Hardy nursery stock propagation guide · Not so easy to contain costs It can be difficult to find what you want when you need it and in the required quantity Potential lack of reliability

Hardy nursery stock propagation guide

Contents

The information in this guide was complied by Andrew Hewson, ADAS. AHDB is grateful to all those who have commented and contributed to this publication.

3 Foreword 4 Propagation management 4 Do it yourself or buy in? 4 Developing a propagation unit 6 Planning, programmes and record keeping 11 Stock plants 20 Clonal selection and plant health 20 Rootstocks 21 Collection and storage of vegetative propagation material 22 Preparation and handling of cuttings 27 Wounding, leaf stripping and trimming of cuttings 29 Rooting hormones 31 Propagation containers 33 Propagation media and nutrition

36 Propagation techniques 36 Seed 46 Cuttings 52 Micropropagation 58 Grafting and budding 72 Division 73 Layering 74 Stooling (mound layering)

76 Propagation environments and systems 76 Influenceofwater,temperatureandlight 77 Understanding the environmental needs of cuttings 78 Light levels and shading 80 Interaction of light and moisture 82 Mist and high humidity environments 86 The role of the Evaposensor 88 Polythene systems 93 Coldframeswithandwithoutplastic 93 Cuttings in the open ground 93 Heated bins 94 Direct sticking of cuttings

96 Aftercare 96 Crop protection 97 Pest and disease control 103 Weed control 110 Post-rooting nutrition 113 Growthcontrol 117 Overwinteringofrootedcuttingsand young liners 120 Aspects of liner production

123 International Plant Propagators Society case studies 123 International Plant Propagators Society 123 Cracking Photinia 124 Hibiscus grafting 125 Lavander propagation – rooting rotters 126 Rhododendron and Azalea propagation 128 SuccesswithHebe cuttings

130 Research and knowledge transfer requirements 130 Propagation management 130 Propagation techniques 131 Propagation environments and systems 131 Aftercare

134 Appendices 134 AppendixI–Dealingwithcommon problems 142 Appendix II – A summary of propagation methodsforarangeofwoodyHNS subjects 147 Appendix III – References and further information 150 Appendix IV – Glossary of terms 151 Acknowledgments 152 Photographic and image credits

Since its inception, AHDB Horticulture has funded a considerable amount of research relating to hardy nurserystock(HNS)propagation.Duringthisperiodandbeforeit,Defraalsosupportedasignificant programme of research and technology transfer on hardy nursery stock plant propagation, much of whichwascomplementedbyAHDBHorticulture-ledwork.Notableexamplesincludeworkundertakenat the former ADAS Experimental Horticulture Stations HRIEffordandLuddingtonandNIABEastMallingResearch station, on stock plant management, chip budding, propagation environments, substrates, nutritionandmicropropagation.Theprincipalfindingsfromthisworkarewidelyscattered throughout numerous project reports and associated references, including EHSs open day handouts, annual reports, summary reports, reviewsand,morerecently,variousAHDBHorticulturefactsheets.Thereisalsoawealthofinformationofvalue to the hardy nursery stock industry from other sources, most notably the Annual Proceedings of theInternationalPlantPropagators’Society(IPPS).However,becausetheinformationissowidelydispersed,itisdifficultandtime-consumingfor growerstoaccessandevaluateitandthenapplyoradaptthekeyfindingstotheirownnurserysituation inordertoimprovepropagationperformance.As a result, AHDB Horticulture commissioned ADAS tocollatethisinformationwiththeprincipalaimsofsummarisingexistingknowledge,criticallyreviewing itandassessingnewadvances,inordertoproduce a practical Hardy nursery stock propagation guide.

For ease of reference, the guide is divided into six main sections, encompassing propagation management, propagation techniques, propagation environments and systems, aftercare, a series of practical propagation summaries from the IPPS and industryresearchandknowledgetransferrequirements.Case studies are featured throughout to illustrate good practiceandshowhowleadinggrowershaveappliednewtechnologiestoimprovepropagationoutcomes.A number of appendices are also included at the back of the guide providing information on dealing withcommonproblemsencounteredanddetailing thepropagationmethodsforarangeofHNSsubjects.While aimed primarily at the experienced propagator, the Hardy nursery stock propagation guide is also intendedforuseasatrainingaidforusewithstudentsandnewstaffmembers.Assuch,itisstructuredin a readily extractable format that can be adapted and usedforbespokenursery-specifictraining.Itisalsoeasy to navigate, featuring signposting to further, importantsourcesofinformation.Theguidealsofeatures numerous illustrations in the form of charts, tables,graphsandimagestoshowandsummarise keypoints.AHDBHorticultureisgratefultoAndrewHewson ofADASforleadingthisworkanddevelopingthe guide.AHDBHorticulturewouldalsoliketothank the IPPS for its commitment and contribution to the projectandeachofthegrowerswhohavecontributedtotheguide,especiallythosewhohaveparticipated inthecasestudies.Ian Ashton, Lowaters Nursery

Foreword

Foreword3

Do it yourself or buy in?Thoughtshouldalwaysbegivenbeforedevelopinganewenterpriseorextendinganexistingonethatitisthecorrectdecisiontobeundertaken.Couldsomeorallof the plant material be bought in from other, specialist suppliers? Is, for example, buying in unrooted cuttings a viable alternative? Might outsourcing be a cheaper, less wastefulandmoreflexibleoptionandonethatdoesn’ttie up capital, space and other resources for lengthy periods?Table1summarisesthebenefitsandrisksbehindthedecision.Thereisn’tastandardanswertothequestionof whethertopropagateorbuyinasdifferentnurserieshavedifferentneedsandmuchdependsonindividualcircumstances.Inreality,growersoftencompromise andfocustheirresourcesonwhattheyknowandgrowwellwhilebuyinginthosecropswithwhichtheyhavedifficultiesfromspecialistproducers.Outsourcingdoeshelp release valuable time and space to focus on other activitiesorcrops.

Plant material can be purchased as unrooted cuttings, rooted plugs or established young plants in 7, 8 or 9 cm pots(liners).Buyinginunrootedcuttingsfromspecialistpropagatorsworkswellforsomebusinesses.Often,such material is imported from the Mediterranean area (notably,Israel)wherestockplantsfromwhichcuttingsareharvestedaregrowninawarmerclimatewithlongerdays,whichmaysuityear-roundproduction.However,supplychainproblemsandassociatedcosts,mayensuewhenbuyinginallkindsofplantmaterialandtheseshouldbetakenintoaccount.Thereisalsoa risk of importing non-indigenous quarantine pest and disease problems and it is also less easy to monitor truenesstotype.

Developing a propagation unitThe principal aim of any propagation enterprise is to produceasufficientnumberofwell-graded,healthy, high-quality plants as economically as possible to securegoodreturns.

Propagation management

Table1.Thebenefitsandrisksofin-housepropagationandbuyingin

In-house Bought in

Benefits Benefits

Quality control and independenceReliabilitytocustomers,self-sufficiencyandsecurityofsupplyOpportunity to exploit market opportunities created by those whohavereducedorabandonedpropagationAttractivetostaffandenablesspecialistskillstoberetainedby the businessUtilises existing space and facilities throughout the yearUsuallycheaperwhereskillsandsuitablefacilitiesarein place and can be developedCloser control of costs and programmingEasiertomanageandcontrolthedevelopmentofnewplantsLessriskofpests,diseasesandweedsbeingbroughtonto the nurseryWorkswellwherecontinuityofsupplyisrequired,especiallysmall runs of less common lines

Obviates need to invest in costly facilities for in-house propagation or to expand existing facilitiesFrees up time for other developmentsSpecialistpropagatorscanofferimprovedquality, uniformityandtheabilitytohelpschedulefinishedcropsFlexibility to respond quickly to changing market trends and requirementsConvenienceFillsin-houseskillgapswherepropagatingskillshavediminishedIn-house time, space and resources are released to use onotheractivitiesorcropsthenurserywantstofocusonUsuallylesswasteifdifficultcropsarelefttospecialistsAvoidance of the need to manage and maintain stock plants

Risks Risks

Space,staffandequipmentaretiedupmakingitdifficulttorespond quickly to market trendsPlant licensing arrangements may preclude in-house propagation of particular plantsStock plants or nursery crops are required to supply propagation materialStock plants require time and space to manageMay not make best use of existing resourcesWastagecanbehighwithdifficultcropsLoss of in-house propagation skills may make propagation of somesubjectsdifficulttocontinuewith

Usually more costly, especially as transport costs riseQuality can be variableCanbedifficulttooutsourcerare,unusualorspecialistplantsNotsoeasytocontaincostsItcanbedifficulttofindwhatyouwantwhenyouneeditandin the required quantityPotential lack of reliabilityMaybringpests,diseasesandweedsontothenurseryRisingcostsofplanthealthinspectionsassociatedwithimported material

4 Propagation management

Planning considerationsAnimportantconsiderationwhendevelopingorextending a propagation unit is to ‘keep it simple’ and staywithinanyfinancialbudgets.Avoidunnecessary,overly sophisticated equipment that may be costly andunlikelytobeused.Expensiveequipmentisn’tnecessarilythebestandsimplesystemswilloftendeliverthemostsuccessfulresults.There are some important points to consider:

• What about planning and building regulations requirements?Theseshouldbecheckedoutwithyour local authority at the start

• Whatcropsaretobepropagated,whichtechniqueswillbeusedandwhatfacilitiesarerequired?

• Whataretheplantnumbersinvolvedandhow muchspaceofwhichfacilitytypeisrequired?

• Willpropagationbecombinedwithlinerproductiononthissite,inwhichcasemorespacewillprobablybe required?

• Will stock beds be used and established on the site, either as an adjunct to existing beds or as replacements?

• In the case of open ground herbaceous, a ‘dirty area’ forinitialdivisionisagoodidea,asisawashing-offarea to keep soil out of the main unit

• Whatotherfacilitieswillbeneeded(includingcoveredworkspace,coldstorage,growingroom,staffroom,carparking,equipmentstorage)anddotheseneedtobeneworcanthenewdevelopmentbelinkedtoexistingworkareas?

• Think carefully about the allocation of space and relationshipsbetweenstockbeds,propagation unitandstorageareas,aswellasaccess

• Whatsortoftransportandhandlingsystemwillbeusedandhowwillthisimpactonsitedevelopment,suchasbedareaandtheirconfiguration,pathwaysand access areas?

• Whereisthebestlocationforthenewor expanded unit?

Site considerationsThe next step is to think about the site and, in particular, thefollowingrequirements.Drainage and shelterChooseawell-drainedandwell-shelteredsiteifpossible,strongwindsaredamagingandcreate heatlossfromglasshouses.Usewindbreakswherenecessary but site these carefully so they give maximumprotectionwithoutcastingundueshade.Asaguide,windbreaksrelativetoaglasshouseblockshouldbeanoptimumheightoftwo-thirdsoftheheightoftheridgeandsitedsothatthedistancebetweenthewindbreakandtheglasshouseblockisthreetimestheeventualheightofthewindbreak.Livingwindbreaksshould be thinned periodically to give 50% porosity

andsoprovideasteadyfilteringofstrongwinds.Internalwindbreaksmaybeneededonlargersites andshouldalsoprovide50%porosityandbewellsecuredagainststrongwinds.Topography and shape of site Ideally, the site should also be reasonably level, that is, slopenomorethan1:75.Theshapeofthesiteisn’tofgreatsignificancebutregularshapesenablebestuse ofspaceandaremucheasiertoworkwith.Layout of site Carefulplanninghelpsmakethemostefficientuseof allresources,particularlymachineryandnurserystaff.Muchofthiswillbeinfluencedbytheprevailingorproposedhandlingandtransportsystem.Duringsiteplanning, take account of common bottlenecks such aspreparationandpottingareas.Thinkcarefullyabout:

• Theentranceareaandgeneralaccess.Preferably,this should be centrally located and lead directly tothecarparkandoffice/staffareas

• Thepreparationareaandproductionstructures.Theseshouldleadonfromtheofficeandstaff areas and combine preparation space for sorting and grading stock plant material, handling and insertingcuttingsandpotting.Locatecoldstorageandgrowingroomfacilitiesnearby

• Anorbitalroad.Thisshouldleadoutfromthe car park, past the production building and service therestofthesite.Itshouldfollowacircularroutebecausethisisusuallymorespaceeffectivethanprovidingvehicleturningareas.Thesurfaceshouldbesmoothandfirm.Awidthof4.5mshouldenablevehicles to pass

• Bedsandpathways.Theseshouldbeofastandardsizeandlinkedwiththechosentransportsystem.Asaguide,thepreferredhandlingdistancefrompathwaytosetting-downpointonabedis2–3m;anywider,thentheworkbecomesharderandslowerand,so,morecostly.Narrowpathsbetweenbedsfortrolleysshouldbearound1mwideandwiderpathssuitableformini-tractors, forklifts and pallet trucks should be 2 m

• Bedconstruction.Bedsusedforpropagationandgrowingonlinersmustbewelldrained;capillarysandbedsareidealforproducinguniformcropswithcleanfoliageandminimumweeds.Permeablemembranescanbeusedtocontrolweedsandrootingthrough.Baseheatcanbeinstalledforpropagation.Heatedfloorsofporousconcreteconstructionmakegood use of space and are easy to clean

• Roomforexpansion.It’snotalwaysnecessary todevelopthewholesiteinonegobutphaseddevelopments should take account of future plans andallowforanypossiblechanges

Water supplyAnadequatesupplyofwatersuitableforcropirrigationisessentialandextracapacitymaybeneededwhenexpandingexistingfacilities.Waterusedinfoggingpropagationsystemsshouldbedrawnfromaclean,

Propagation management 5

directmainssupplytohelpsafeguardstaff(fromcontracting Legionellaviainhalationofthefog).Enclosingfogunitswithinhighpolythenetents providesafurthersafeguard.Water quality is particularly important for propagation, especiallywheremistandfoggingsystemsaredeployed.‘Hard’waterislikelytoblockjetsovertimeand discolour crop foliage and high salt levels may alsoscorchseedlingsorcuttings.Highwateralkalinity(above200mg/lcalciumbicarbonate)canalsotriggerexcess callusing of cuttings and be detrimental to rooting.Acidificationofirrigationwatershouldbeconsideredifwateralkalinityisanissue.Power supply Anadequateandreliablethreephasepowersupplywillbe required for lighting, supplementary lighting, heating andgeneraluse.

Layout of propagation structures Multi-span constructions make the best use of available space,withcompartmentsforaccommodatingdifferentpropagationorgrowingzones.Integratingareasinthiswayisefficientandprovidesflexibility.Work areas should be in a dedicated space that is linked internally to the propagation areas to increase the speed ofhandlingofsensitivecuttingmaterial.Productionhouseswithcorridorsareideal.Keypointsinclude:

• Check planning and building regulations requirementswithyourlocalplanningauthoritybefore developing anything

• Cost items out carefully to ensure you have an adequate budget

• Design propagation beds or benches around an integrated materials handling system and ensure all work,propagationandgrowingareasarejoinedup,such that plant material can be seamlessly moved from onetoanotherwhenready,preferablyundercover

• Include a plant material storage area for cutting preparation and one large enough for receipt of bought-in plant material such as rooted plugs or liners

• Usemobileworkbenches,withwipe-cleansurfacesforflexibilityandeaseofcleaning

• Avoidclutterandmakeworkareascomfortable withadequateheatandgoodnaturallight

• Use sliding doors for easy movement of materials andtoincreaselightandventilationwhenrequired.Makesurethewallsandroofareinsulated to conserve heat energy

• Allowsufficientspaceforgood,safeaccessbothinsideandaroundtheglasshouse;mainpathwaysshould accommodate pallet trucks

• Gantry systems make excellent use of available space in and around propagation areas, functioning eitherasworkplatformsorirrigationboomsbutthey are costly and require large areas of free, unobstructedspacetowork

Thefollowingtwocasestudies(overleaf)illustratehowtwoleadingnurserieshaveplannedanddevelopednewpropagationfacilities.

Planning, programmes and record‑keepingPlanningPlan ahead to ensure adequate resources, including staff,facilitiesandpropagationmaterialsareavailablewhenrequired.Propagationfacilitiesareusuallycostlyso they need to be at or near to full capacity for as muchoftheyearaspossible.Insituationswhereyear-roundpropagationisnotfeasible,suchfacilitiescouldbeprofitablyusedfor otherpurposessuchasgrowingonlinersorshort-termcontainer-growncropstomaximisethroughput.Heatedbedsorfloors,forexample,canbeusedforspringandsummercuttingsandwinterbenchgrafting.Coldframesorsuntunnelsoftensufficeformanyconifer,heathers,semi-ripeandhardwoodcuttings.Some aspects of propagation such as bench grafting alsorequireskilledandexperiencedstaffwhileothertaskslikesummerandwintercuttingpreparationcan befrequentlyundertakenbyseasonalstaffwhohavereceivedthenecessarytraining.Ensuresufficientspaceisavailableforrootedcuttings tobeweanedandyoungplantstobegrownon.

Devising a propagation programmeMost nurseries have some form of propagation programme,devisedaspartoftheforward-planningprocess,whichshouldreflectstaff,spaceandpropagationmaterialrequirements.Thereisnostandardprogrammeand,whiletheyusuallyvaryintheirlevelofdetail, sophistication and the method of presentation, theyneednotbecomplicated.The programme should focus on crops that suit the availableskillsandfacilities.Ideally,theseshouldbe those in short supply that can be propagated successfullyin-housewiththebestreturnsandlowestriskoffailure.Buyinthosethataredifficultoruneconomictoproducein-houseorwheremarketdemandisuncertain.Successfulpropagationdependsongoodtiming,whencuttingmaterialisintheoptimumconditionforrooting.Thisismorecrucialwithsomesubjectsthanothers, for example, the spring propagation of deciduous Azalea, Magnolia and Syringafromsoftwoodcuttings.Cuttings of some herbaceous subjects must be taken whenvegetativeratherthanfloralforbestresults,forexample, Epimedium,whichisbesttakeninlatespringafterflowering.Similar remarks apply to seed harvesting and germination,aswellaspropagationbygrafting andbudding.


Case study 1: West End Nurseries Preparing and planning for a new propagation unitWestEndNurseriesinDevonisrunbyPetervanDelft and specialises in the propagation of shrubs andclimbersforthetrade.Theyinvestedinanewfacilityin2000toimproveproductionefficiency andsatisfyarisingdemandforqualityliners. “Itwasbecomingmoredifficulttobuyintheplantsthatourcustomerswantedandpriceswereincreasing, exacerbated by rising transport costs,” explainsPeter.“Withsomecompetitorsabandoningpropagation,wealsofeltinvestmentwastimely,enabling us to improve service levels to our customers,”headds.“Throughout the planning process,” Peter continues, “beawareofthemarketaroundyou;itmaybethatfor some lines it becomes more economical to buy in;changesoccurrapidlyandyourplansneedtobesufficientlyflexibletoenableyoutorespondquickly.Also,clearlyestablishwhatyouneedfromthenewunit;atWestEndNurseries,weneededimprovedefficiency,morecapacity,greaterflexibilityandreduced running costs and, so, factored these intoourplanning.“Wealsowantedtogrowbetterqualitylinercropsbyreducingstressonourpropagationmaterialwithbetterfacilitiesimprovingtherootingofcuttings.Higher productivity can be achieved by shortening rootingtimesandimprovinglabourefficiencyandtheworkingenvironmentforstaff,”advisesPeter.He continues, “When planning, stay abreast of researchdevelopmentsandnewtechnologies, too;wewereespeciallykeenonusingIPM,improving disease prevention and reducing rooting times.Whenmakingabiginvestmentlikethis,tryalso to make it as ‘future-proof’ as possible so that it doesn’t become dated or constrain expansion goingforward.Weaimedtoensureournewfacilitywouldenableustoexpandanddevelopnewmarkets.Flexibilityisthekey.

Try to also build in safeguards through thorough risk assessments and plan contingencies in case offailures.“When it comes to site preparation, ensure the terrainissuitableandyoucancopewithdrawbacks;ournewunitisonaslopingsite,sowehadtoputinamechanicallifttomoveourbenchesbetweentwolevels.Thelocationoftheunitwithinthenurseryandaccesstoitarealsoimportantconsiderations.Remember too, that it’s very easy for costs to spiral, soallowfora20%overruninyourcostingsandbesuretohavefullcontroloveralldevelopments.Think,too,aboutstaffresourcesasthiscanmakeorbreaktheefficiencyofanewenterprise;somestaffmayneedtorelocate,travelfurtherorlearnnewskills.

Mobile benching in the propagation unit

“Think about your plant range in relation to the plannedfacilities;theremayinfactbescopetoexpandthisandgrowcropspreviouslynotpossible.Conversely, a more specialist approach could be the wayforward.Balanceopportunitieswiththerisks ofoverproduction.”WestEndNurseries’carefulplanningledtothecompletionoftheirnewpropagationunitin2003,featuring 2,350 m2ofVenlostyleglasshousewith 13spans,rollerbenches,workbenchesforpreparingand sticking cuttings, a scissor lift to move benches betweenthetwolevelsofthepropagationhouse,environmental computer control, thermal shade screening,acoldstoreandweaningunit.Reflectingontheprojectfollowingcompletion,whilePeterispleasedwiththeresults,healsorecognisessomeerrors.“Eventhoughweplannedcarefully,wedidmakemistakes,”hesays.“Wedidn’tallowenoughtimetolearnhowtousethenewfacilitybeforeitwascommissionedanditshouldhaveincludedmorestoragespace.Wealsodidn’tsetasidesufficientfundstocompletetheunitinitsentirety.Insomecases,wealsoreliedtooheavilyonadvicefromconsultantsratherthanourownknowledge,”heconcludes.

Amechanicalliftallowsbenchestobemovedbetween twolevels


Case study 2: Palmstead Nurseries Ltd Developing a new propagation unitKent-basedPalmsteadNurseriesLtdgrowsawiderangeofnurserystockforthelandscapeandamenitymarket,includingcontainerandfield-growncrops.Theypropagatemuchoftheirrequirement,usingacombinationofmainlyfield-grownstockplantsandnurserycropsforpropagationmaterial.The nursery employs a range of propagation methods, mainly cuttings but also seed (early spring sowingsdirectintomodules),division(variousherbaceous and grasses) and bench grafting using hot-pipe callusing (Betula, Fagus, CorylusinwinterfollowedbyHamamelis and Viburnuminsummer).Evergreen Prunus are direct stuck during late September to early October and rooted cold under contactpolythene,acheapandeffectivewayofpropagatinganimportant,highvolumecrop.In2010,PalmsteadNurseriesopeneditsownbrandnewpropagationunittoboostin-houseproductionand meet the rising demands of the nursery for uniform,high-qualityliners.Occupying an area of one hectare and costing intheregionof£1million,thenewunitcomprises a multi-span glasshouse block that integrates four differentenvironmentalzonesforpropagationandweaningwithgrowingonbedsforrootedcuttingsandaworkareaforpropagation.At£1million,theunit represents a substantial outlay but the business is committed to propagation and keen to be as self-sufficientaspossible.“Weenjoypropagationandwanttodomore,”saysYoungPlantsManagerGeoffDeLaCour-Baker.“Ourneedforyoungplantscontinuestogrowandwelikethequalitycontrol,flexibilityandself-sufficiencythatin-houseproductiongivesus.We’doutgrownouroldspaceanddecidedtoinvestinnewfacilitiestokeeppacewithdemand,”hesays.The facility combines sophisticated environmentally controlledpropagationzoneswithspaciouscompartments for accommodating rooted material andliners,allunderoneroof.

NurseryTechnicalManagerLeeWoodcockexplainsmore.“Akeyfeatureofthefog/mistbaysisthatwenowhavetheabilitytoalterthemistingfrequencyof each bay independently, giving us the option of weaningin-situ,ratherthanmovingthewholebayintoadrierareatowean,whichislabourintensive.Ourcomputerisedmistingsystemalsoallowsustosetupaweaningprogramme.Plantscanbeweanedover any period of time by setting the programme to gradually decrease the misting frequency over a periodofaweek,twoweeks,amonthorwhateverisrequired.Thisgradualweaningoffreducesthestresstothecuttingsandlossesfromweaningare athingofthepast.“The computer system is really the hub of the unit andwebelieveitisuniqueintheUK.Itisriggedupto a number of sensors measuring light, temperature and relative humidity, to calculate the vapour pressuredeficit.“Energyscreensarealsoafeatureofthenewunit,toconserveheatandforshading.“Wedidourhomeworkandgotoutandaboutbeforefinalisingourplans,visitingdifferentgrowerstoseewhatwasavailableandgleanknowledgefromtheirexperience,’’saysGeoff.

Currently, transport and handling evolves around Danish trolleys but there are plans to install conveyors to ease and speed the movement of plant material.“Wedesignedthelayoutoftheblocksoithasalogicalflowtoit,”continuesGeoff,“startingwiththeworkareawherewepreparematerial,leading to the propagation compartment and weaningzones,thenthroughtothegrowingonbeds,wherewehaveamixofrootedplugsand8cmliners.“Water is disinfected using chlorine dioxide, whichhelpstokeepfog/mistnozzlesfreeofalgae;we’vealsofoundithelpscontrolvariousleaf-spotproblems on crops like Hebe, Hedera, Lavandula and Viburnum tinus,”addsGeoff,“andweuseJet5todisinfectourpathsandbedsasweplaceabigemphasis on maintaining good nursery hygiene, especiallyinourpropagationareas.”

Energy saving shade screens being pulled over a crop

Fog/mistingsysteminthepropagationunit


Thelengthoftimerequiredforpropagationwillvary withsubject,timingandavailablefacilities,forexample,cuttings propagated using basal heat usually root quickerthanthosewithout.Thereisalsoaneedtobeawareofhowlongcuttingsandseedswilloccupypropagationspaceinordertoplanthroughputsandmakethebestuseofresources;thisunderlinestheneedtopropagatematerialwhenit isintheoptimumconditionforrapidthroughput.Table2.Examplecalculationtodeterminecutting numbers required

Stage % losses Plants remaining

Total plants required 100 1,000

Losses during rooting 10 900

Losses during establishment 10 810

Other losses 10 729

Unsaleable 10 656

When calculating the number of plants to propagate, thefollowingfactorsneedtobeconsidered:

• Final total of plant numbers required (use sales data and market information)

• Germination or rooting percentage

• Establishment losses during propagation

• Losses due to pests, diseases or other cultural issues

• Wastage (unsaleable or poor quality plants)10cuttingsarerequiredtoobtain6.56rootedplugsorliners.Therefore,thetotalnumberofcuttingsrequiredfor 1,000 rooted plugs or liners is 1,525 (1,000 divided by6.56x10)asshowninTable2.

Record-keepingSuccessful propagation requires disciplined record-keepingandattentiontodetail.Someform of diary or record sheet is a useful reference point, particularlyforfutureplanningandwhenstudying thecasehistoriesofparticularcrops,especiallywhendiagnosing losses or seeking a better understanding ofsuccesses.Figures1,2and3showexamplepropagationandweaningrecordsheets,whileFigure4showsanexample propagation best practice sheet devised by aleadingnurseryforstafftraining,qualitycontrolandmonitoringpurposes.Eachoftheseexamplescanbedevelopedandadapted.Table3(overleaf)showsanexampleofanannualpropagation programme suitable for nurseries able to employawiderangeofresourcesbutwhichcanalso beadaptedforthosewithmorelimitedfacilities,systemsorrequirements.

Plant name...........................................................................................................................................................................................................................

Propagation method...........................................................................................................................................................................................................

Propagation date _ _ /_ _ /_ _ _ _ Potting date _ _ /_ _ /_ _ _ _ Sales date _ _ /_ _ /_ _ _ _

Planned Actual

Salesrequirement(finishedplants)

Losses during rooting

Losses during establishment

Other losses

Unsaleable

Cuttings required

Location................................................................................................................................................................................................................................

Propagation space required (m2)..........................................................................................................................................................................................

Growingonarearequired(liners/plugs)................................................................................................................................................................................

Planned Actual

Propagationdate(weeknumber)

Propagation source

Labourrequired(manhours/days)

Personnel involved

Comments

Figure1.Examplepropagationrecordsheet


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Qua

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_ _ /_ _ /_ _ _ _

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Figure2.Examplepropagationchecksheet(Quality and uniformity scores: Poor = 1, Acceptable = 2, Good = 3, Excellent = 4)

Batch number Week started

Block weaned

(Y/N)

Percentage weaned Quality Uniformity Date Signed

off

_ _ /_ _ /_ _ _ _

_ _ /_ _ /_ _ _ _

_ _ /_ _ /_ _ _ _

Comments:

Cutting source Stock plants and nursery crops

Location of cutting preparation Propagation unit

Ripeness of wood Softwoodcuttings

Rooting medium and tray Fertis84/100

Preferred tools Red snips

Type of cutting Nodaltip

Rooting hormone ChryzoponRose(0.1%IBA)

PPE required Nonerequired

Propagation environment White plastic

Prone to Botrytiswheninflower

Rooting requirements Removeflowers,otherwisewon’trootwell

Weaning requirements 48hoursunderfleece

Other notes

Work rates 2010 2011 2012

Target Actual Target Actual Target Actual

Collection of cuttings

Preparation/insertion

Grade/weantrays

Figure3.Exampleweaningchecksheet

Figure4.Examplebestpracticerecordsheetforstafftraining,monitoringandqualitycontrol(Abeliaxgrandiflora)


Table3.Exampleofanannualpropagationprogramme

Method Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Seed under glass

Seed outdoors

Micropropagation

Softwoodcuttings

Semi-ripe cuttings (deciduous)

Semi-ripe cuttings (evergreens and conifers)

Leaf-bud cuttings

Hardwoodcuttings

Root cuttings

Division

Layering and stooling

Budding

Bench grafting

Field grafting

Optimum periods Other potential periods

Itisnotanticipatedthatnurserieswilluseallofthesetechniques,ratheraselectiondependingoncropsandresources.

Stock plantsManyeasyrootingHNSsubjectscanbereadilypropagated from nursery crops, provided they are healthy.Dedicatedstockplants,however,enablegrowerstoexercisequalitycontrolfromthestartoftheproductionprocessandareespeciallyusefulforslowgrowingordifficulttorootsubjects,forwhichnurserycropsmaybeunabletoprovidesufficientmaterialoftherequisitequalityattheoptimumtime.While stock plants may be costly to have and maintain, most propagators use them for at least someoftheirrequirements.Theyoffersecurityof supplyandenablecropstobepropagatedatspecifictimeswithinascheduleandwheninoptimumcondition;container-grownmotherplantsforcedunderprotectionforearlyseasoncuttingsareanexampleofthis.HRIEfford(formerlyknownasEffordExperimentalHorticulture Station) undertook a considerable programme of research into stock plant management and quickly demonstrated several advantages, notably the ability to collect cutting material at the optimum time for propagation and a marked improvement in theuniformityofgrowthwithinbatchesofplants. Adisciplinedmanagementprogramme,whichincludednutrition, irrigation, crop protection and pruning to manipulategrowth,alsoprovidedevenflushesofgrowth,enablingeasyselectionofuniform,gradedmaterial. Well-managed stock plants


AlloftheHRIEffordstockwasclonalinorigin,selectedfor trueness to type and propagated from selected motherplants.Pruning techniques and the preconditioning of cutting material (by etiolation or partial blanching using blackouts placed over stock plants early in the season orbywrappingstemsectionswithblacktapetoexcludelight)toimproverootingofdifficultspeciesfeaturedinacomplementaryprogrammeofworkatNIABEastMallingResearch(NIABEMR).The management and manipulation of stock plants for theproductionofleafycuttingswasalsoconsidered inanAHDBHorticulture/Defra-fundedprogrammeofworkundertakenatNIABEMRdevisedtoprovideHNSgrowerswithabetterunderstandingofhowtocontrolgrowthandoptimisecuttingproduction.

Practical aspects of stock plant managementAwell-managedstockbedareaprovidesnurserieswithhigh-quality,well-gradedcuttingsthatareanessentialpartoftheproductionprocess.Theyalsocruciallyprovide security of supply at the optimum time forpropagation.Well-managed stock plants provide propagation material ofknownhealthstatusandshouldbefreefrompestsanddiseases,includingvirusinfection.Weedscanalsobekeptunderclosecontrol,whilenutritionandpruningcanbefocusedandcarefullymanaged.Field-grownstockplantsareanespeciallyusefulsourceof clean cutting material for crops regularly troubled by leaf spot diseases such as Berberis, Camellia, Hebe and evergreen Prunus,whichtendtobemoreprevalentamongcontainer-grownplants,especiallywhereirrigatedoverhead.High-quality plants that are clonal in origin, true to type, propagatewellandareofknownhealthstatus,providethe best and most reliable stock plants and, in turn, high-qualitypropagationmaterial.When selecting clones, ensure they are correctly named andlabelled,ofgoodformandhighrootingpotential.Keepanoteofthedonororsourceofeachplant,batchorblockforfuturereference.As a general guide, the number of stock plants required should be based on average yields of 25 cuttings per plant during the second year of establishment, rising to 50 cuttings per plant in year three, 100 cuttings per plant in year four and 150 cuttings per plant from year fiveonwards.ResearchatHRIEffordestablishedthatyields may be higher, especially if several grades of cuttingsaretakenovertime.Allowatwotothree-yearestablishment period before harvesting propagation materialregularly.Stock beds should be located near to the propagation areatosavetime;cuttingmaterialshouldspendaslittletime in transit as possible, particularly soft, summer cuttingmaterial.Chooseawell-shelteredsitewithwindbreaks,ifnecessary,andfenceagainstrabbitsanddeer.

Avoidfrostpocketsandheavilyshadedareaswithpoorlightlevels.Selectawell-drainedbutmoistureretentive mediumloamsoilwithaneutralpH(6.5to7.0)thatwillaccommodatemostspecies.Ericaceousorcalcifugesubjects such as Camellia, Crinodendron, Enkianthus, Hamamelis, Hibiscus, Magnolia and Skimmia require alowpHsoil(4.5to5.5),asdomostconifersandheathers.Undertakesoilanalysespriortoplanting andapplybasedressingsaccordingly.Top-dress withafertiliserinearlyspring.

Field-grownstockplants

Alpines,heathersandotherlowgrowingsubjectsshouldbeplantedonraisedbedstoaidwinterdrainageandreducesoilsplashontofoliage,whichcanspreaddiseases, notably Rhizoctonia, a common problem onheathers.

Plantsgrowingonraisedbeds

Soil-grownplantscanalsobehousedunderprotectionviamobileshadetunnelsinfieldsituationstoprovidefurtherflexibility.Keeparecordandsketchaplanofwhatisplanted,andwhereandwhenforfuturereference.Thisalsosavestime,particularlywhenharvestingcuttingsonlargersites.


Allowenoughspacebetweentheplantsandtherows toenableeasyaccessandmanagement.WithslowgrowingspeciessuchasCamellia and Rhododendron, whichproducefewercuttings,plantdoublethenumberrequired to provide increased numbers of cuttings earlyon,beforeremovingalternateplantsasgrowthincreases.Table4canbeusedasaguidewhendecidingonstockplantspacing.Table4.Stockplantspacing

Vigour In row spacing (m)

Between row spacing (m)

Slowgrowing(e.g. Camellia) 0.6–0.9 0.9–1.2

Medium(e.g.Berberis) 0.9–1.2 1.2–1.8

Fast(e.g.Buddleia) 1.2–1.8 1.8–3.0

Spacealpines,heathersandotherlowgrowingsubjects, including some herbaceous perennials at 0.45mx0.45mor0.6mx0.6mdependingonvigour.Highnumbersofstockplantscanbegrownwellinrelativelysmallareas,forexample,withstockplanthedgesspaced3mapartand45cmintherow,6,500stockplantscanbegrownperhectarealthoughadditionallandwillberequiredtoaccommodatereplacementplantingstoensurecontinuityofsupply.

Stock plant husbandryA summary of the month-by-month cultural requirementsofHNSstockbedscanbefound inTable5attheendofthissection.Soil preparationPreparesoilsthoroughlyandwellinadvanceof planting, using bulky organic manures to boost fertility andimprovestructure.Avoidsitesknowntohaveahistory of soil-borne diseases such as Phytophthora species or Verticillium dahliae.Checksshouldalsobe carried out for root invading nematodes such as Pratylenchus species and Xiphinemaspecies.Weed controlPerennialweedsincludingbrambles,bindweeds, couchgrassandthistleshouldbedealtwithwellinadvanceofplanting.Usepermeablegroundcoverfabricsormulchesforsafeandeffectiveweedcontrolaroundstockplants,particularlywhiletheyestablish.EarlyworkatHRIEffordwithpolyethylenemulchesfound that cutting quality during drought periods did sufferwithoutirrigation,andsubsequentplantings hadlow-levelwateringsystemsinstalledunderneath themulch.Residual herbicides can be considered once stock plantsareestablishedbutshouldbeusedwithcare;verysolubleproductsmaycausedamage,checkgrowthorpossiblyreducetherootingpotentialofcuttingmaterial.Crop protectionStockplantsshouldbegrownlikeothercommercialcrops, monitor them regularly for pest or disease

problems.Useintegratedcropmanagementtechniquesincludingbiologicalpestcontrolwherepractical,toreducepesticideinputs.IrrigationIrrigate stock plants during dry periods and, for best results, at least 24 hours before removing cutting material.Goodrootingrequirescuttingmaterialtobecool,freshandturgid;similarremarksapplywithbudwood.SubjectssuchasdeciduousAzalea and Ilex are especiallysensitivetodrought,whichreducesextensiongrowthandcuttingquality.Mulchescanalsobeused toconservesoilmoisture.NutritionMaintainthenutritionalstatusofthestockplantswithregularfertilisertop-dressingsbutdon’tover-dothis; anexcessofnitrogen,forexample,willproduceverysoft,lushgrowthunsuitableforpropagation.Forthisreason,verysofttipgrowthisusuallydiscardedwhenpreparingsummercuttings.Asageneralguide,field-grownstockplantsshould betop-dressedwitha2:1:1fertiliserannuallyeach spring, augmented by the outcome of soil analyses everythreeyears.However,accountshouldbetakenofthedifferingrequirementsofslowgrowingconifers,saltsensitiveericaceoussubjectsandquickgrowing,more vigoroussubjects.Container-grownstockplantsshouldbemonitored morefrequently,withgrowingmediaanalysesundertaken each spring and supplementary nutrition providedasrequiredtomaintainvigour.Plantswill alsorequirerepottingintofreshgrowingmediaorpotting-on into larger pots, periodically depending upon plantvigour.Stock plants should also be liquid or foliar fed, for example, using a 1:2:1 fertiliser during periods of active growthtomaintainqualityandboostphosphatelevelsaheadofcuttingspropagation.Routinemicro-feeding ofstockplantswithcompostteaswillprovidesupplementarynutrition.Littledetailedworkappearstohavebeendoneon the nutritional requirements of stock plants and, in particular, the merits of using supplementary feeding toimprovetherootingpotentialofcuttings.ShadingWorkatHRIEffordfoundthatshadingsignificantlyimprovedthequalityofgrowthandcuttingmaterial ofmanyHNSsubjects,notablyAzalea, Camellia, Eucryphia, Magnolia, Pieris, Rhododendron and Skimmia.Othersubjectsthatrespondwellinclude ferns and various herbaceous perennials, such as Anemone x hybrida, Epimedium, Heuchera, Hosta and Pulmonaria.Inmoreexposedareas,fullerprotection may be required for evergreen subjects inwinter.Shading heather stock plants during the spring and summerperiodreducesflowerinitiationandincreasesthenumberofcuttingsperplant.


Shade provision over evergreen stock plants

Grouping plants togetherPlantswithsimilarculturalrequirementsshouldbegrouped together, for example, deciduous stock, evergreenstock,conifers,climbers,etc.Thisenablestheir cultural requirements to be considered more fully andeasestheharvestingofcuttings,asmaterialwithineachblockshouldbereadyoverasimilartimeperiod.Growing stock plants under protectionWorkatHRIEffordexamineddifferentformsofprotection to manipulate stock and provide greater managementflexibility,aswellasimprovedcuttingquality.Shorttermpolyethylenecoverswereusedsuccessfully to accelerate cutting production of HydrangeawithplantsbeingcoveredduringApril andMaywhileAcer, Magnolia and deciduous Azalea weregrowninwalk-intunnels.Shade structures also gave marked improvement in quality for several high-value subjects needing protection from bright summer sun, including: Acer, Azalea, Camellia, Mahonia, Photinia, Pieris and Rhododendron.

inwinter.Stockplantsgrownunderprotection

Glasshouse structures can be used to force high-valuestockgrownincontainers.Growingsuchplants in containers enables them to be moved outside

forarestingperiod,althoughproductioninthiswayisshorttermandusuallyrestrictedtoacycleoftwoorthreeyears.Artificiallightingcanbeusedtoadvancethegrowthof stock plants, for example, Clematis, to enable the rooting season to be extended and a greater number ofcuttingstobeharvestedfromeachplant.

PruningResearchhasshownthatpruningisanessentialpartofgoodstockplantmanagement.Itinfluencescuttingyield, quality, rooting potential and timeliness and this can be exploited to aid crop scheduling, raise productivityandimprovecuttingquality.Theuseofdifferentpruningtechniquesenablesthenumber,timing and quality of cuttings produced to be managed, althoughtheoptimumpruningtechniquevarieswithsubjectandobjective.AtHRIEfford,pruningwasregardedasoneofthemost important annual management tasks to maintain juvenility for enhanced rooting, increase cutting numbers,initiateapredictable‘flush’ofmaterialofoptimum size and condition and shape plants to enable easyaccessandharvesting.Juvenileplantmaterialusuallypropagatesmorereadilythanmaturewood,especially in terms of cuttings, largely due to it having greatercarbohydratereservesandfewerlignifiedcells inprimarytissues.To maximise cutting yield, stock plants should be prunedlightlyduringearlyspringpriortogrowth,harvestingthecuttingsduringJune.TheprocessofcuttingremovalwillalsostimulatefurthergrowthflushesthatcanbeharvestedduringJulyandAugust.Alaterharvest may also be possible but cutting quality and, inturn,rootingpotentialmaydecrease.Hard pruning of stock plants in early spring, by removingathirdtoahalfoftheoriginalframework willreducethecuttingyield,butthecuttingsgeneratedwillbelargerandstronger.Ingeneral,suchcuttings root and establish better later in the season than cuttings taken from lightly pruned stock plant hedges, especiallyinthecaseofmoredifficulttorootsubjectslike Garrya elliptica.WorkundertakenatHRIEffordindicatedthatHydrangea, Hypericum, Potentilla, Senecio and Syringa responded welltostoolingwhileDeutzia, Forsythia, Philadelphus and Weigela should be pruned back by at least half eachyear.Deciduous Azalea and Viburnum should be pruned backbyaboutaquarteronly.Ilex aquifolium responds welltolightpruningregimes,supplementedperiodicallywithrenewalpruning,duringwhichaproportionoftheolderwoodisremovedtomaintainjuvenilityandvigour.Camellia and Viburnum x bodnantense also respond welltotheperiodicremovalofolderwoodundertakenonathree-yearcycle.Mostconifersrespondwelltolightpruningortrimming;formanycultivars,theremovalofcuttingmaterialsufficeswithouttheneedforfurtherformativepruning.


To maximise cutting production throughout a season, theremovalof50–80%ofthepreviousyear’swoodconsistentlygavethebestresultswitharangeofsubjectsatNIABEMR.Suchpruningalsoenabledbatchproductionofcuttingstobeundertaken,withuptothreeseparateharvestsbeingfeasible.ResearchatNIABEMRfoundtheextenttowhichfloweringwoodisremovediscritical;inearlysummer,floweringsubjectslike Philadelphus and Weigela, pruning should be sufficienttoremoveflowerbuds,otherwisesubsequentshootproductionwillbepoor.WorkatNIABEMRfoundthatresponsedifferencesto pruning regimes also persisted for quite some time withcuttingnumbersstillbeinggreaterfromlightlyprunedstockplantscomparedwiththosethatwerehardpruned,some15monthslater.Cuttingyieldinthesecondyearafterpruningwasnotsignificantlyaffectedbyheavyharvestingofcuttingsinthepreviousyear.Inthe case of Garrya and Philadelphus, for example, yield actuallyincreased.Older stock plants can sometimes be regenerated by hard pruning or ‘stooling’, usually in February and March, cultivars of Cornus, Malus and Salix often respondwelltosuchtreatment.However,severepruning regimes often delay the production of cuttings inslowgrowingsubjectssuchasViburnum carlesii ‘Aurora’byuptofourweeks,withanattendant fall-offinrootingpotentiallaterintheseason.Thetimingofpruningworkisimportantandvarieswithsubject.AtNIABEMR,subjectssuchasForsythia x intermedia ‘Lynwood’LA79andGarrya elliptica‘JamesRoof’ responded better to early pruning (March), in contrast to Philadelphus‘Virginal’LA83wherepruninginMayyieldedmostcuttings.AtHRIEfford,theworkwasusuallydoneinApril,withtheseverityofpruninglargelydependentonspecies.However,stoolingwasusuallydoneduringFebruaryandearlyMarch.Commercially, annual pruning is usually done in late winterorearlyspringtomaintainjuvenilityandsoimprovetheyield,rootingpotentialandgrowthpotentialofcuttings;assuch,itisanessentialpartofgoodstockplantmanagement.Containerstockplantsofquickgrowingcropsunderprotection may be trimmed several times during the season as cuttings are removed, for example: Abelia, Ceanothus, Choisya, Cistus, Clematis, Fuchsia, Hebe, Hydrangea, Jasminum, Lonicera, Pieris, Senecio and Spiraea.Herbaceous stock is usually cut back during the dormantautumnandwinterperiod,whendivision mayalsobeundertaken,forexample,withAster, Astilbe, Geranium, Hosta, Helenium, Heuchera and Rudbeckia. With Nepeta,ifplantsarecutbackwhenflowering,theywillproduceaflushofvegetativebasalshootsforpropagationthatrootwell.Alpines, heathers and herbs can be pruned or clipped backwhencuttingsareremovedforpropagation,usuallythroughoutthesummermonthsorafterflowering.

PreconditioningIn this context, the term preconditioning refers to the etiolation or partial blanching of cutting material toimproveitsrootingpotential.Coldstoragetodelay cutting material and forcing stock plants under protection to advance material availability are other recognisedpreconditioningtechniques.Essentially, the dark preconditioning of shoots prior to cutting removal raises the level of endogenous auxin, the naturally occurring plant hormone that stimulates root initiation, thereby helping to improve percentage rooting, rootquality,speedofweaningandsubsequentgrowth.Preconditioning is undertaken to increase the rootingpotentialofcuttingstakenfromdifficult torootsubjects.Thistechniquecanbeusedforrecalcitrant species, initially on a trial basis to build confidence.Darkpreconditioningcanalsoimprove rootquality,speedofweaningandsubsequentlinergrowth.AtNIABEMR,Corylus avellana ‘Aurea’ plants, forexample,reached0.5mbytheautumnofthepropagationyearwhengrownunderprotection, whilecultivarsofSyringa comfortably exceeded thisheightwithinayearfrompropagation.Establishedstockplanthedgesarecoveredwithventilated black polythene clad frames prior to cutting collectioninspringorearlysummer.Alternatively,container plants can be palletised and moved into adarkroomortunneltopreconditionshoots.ResearchatNIABEMR(AHDBHorticultureproject HNS41:Stock plant management and reconditioning) found that dark preconditioning plants during late May andthenpropagatingfromthesethreetofourweekslater,followingweaningtheplantsbackinto50%light,raisedtherootingabilityofdifficultsubjects,andledtobetterrootquality,improvedspeedofweaningand linerthroughput.Container-grownstockplantsalsorespondwellto preconditioningand,whilecuttingnumbersmaybefewerthanwithstrongerfield-grownplants,theyoffergreaterflexibilityintermsofforcing(underglass)ordelaying(usingcoldstorage)cuttingproduction.Wrappingstemsectionswithblacktapetoexclude lightisanotherwaytodarkpreconditionshootsand hasbeenshowntoimprovetherootingof‘difficult’speciessuchasM9rootstocksforfield-workingandcultivars of Syringa.Preconditioning stock plants using darkness for a two-weekperiodinspringtoearlysummerisunlikely to reduce cutting yield in the propagation year, or stock plantvigour.

Cutting storageCutting material should be labelled and stored in shallowtrays,boxesorwhitepolytheneorhessian bagstokeepthemcool;coldstoresareidealandremovefieldheat.Asaguide,around3°Cand90%relativehumiditywillsufficeformostsubjects.Materialshouldbeusedquicklyandlong-termstorageavoided.


Container-grown stock plantsContainer-grownstockplantsgiveflexibilityandcan be forced under protection for early cutting material orpreconditionedtoimproverooting.Subjectssuch as Azalea (deciduous), Cotinus, Exochorda, Magnolia and Syringarootwellfromsoft,juvenilecutting materialtakenearlyintheseason.Supplementarylightingcanalsobeusedwithstockplantsunderprotectiontoextendtheperiodoverwhichcuttingsareavailableandtoincreasecuttingyield.Containergrowingisusefulforalpines,heathersandmany herbaceous perennials and associated subjects propagated from cuttings throughout spring and summer such as Aster, Astrantia, Campanula lactiflora/latiloba, Delphinium, Penstemon and Salvia nemorosa. Cultivars of bearded Iris and Hemerocallis can also be propagatedfromsummerdivisions,forwhichstockplants are especially useful, due to the large quantities ofmaterialrequired.Alpinesandheathersgrownthrough 9 cm to 3 litre pots over a three-year timeframe makeidealstockplantsforscheduledproduction.

inwinter.Alpinesgrownin3-litrepotsmakeidealstockplants

Container-grownstockplantsalsopermitbatchorscheduledproductionofHNSsubjectsrequiringtimelyandsequentialsuppliesofuniformcuttings.

Stock plants for root cuttingsFor propagation using root cuttings, young stock plants eithergrownincontainersortheopengroundprovide the best propagation material, the former obviating the time-consumingtaskofliftingfromthefieldpriortoremovingrootmaterialforcuttings.Theuseofpeat-basedgrowingmediawithcontainer-grownstockplantsalsopromotesthedevelopmentofyoung,fibrous,activelygrowingrootmaterialidealforpropagation.Iffield-grownstockplantsarepreferred,bulkyorganicmatter should be incorporated as soil conditioning prior toplantingtohelppromoteactiverootdevelopment.Irrigationisessentialindrysummerweathertopromotemaximumrootgrowth.Field-grownstockplantsshouldbeliftedfromthegroundandthesoilgentlyshakenawayfromtherootstoenablesuitablerootmaterialtobeselectedandremoved.Withlargefield-grownplantsthatcannotbelifted,thesoilshouldbescrapedawaytoexposetherootsforuseandcollection,afterwhichthesoilshouldbereturnedandfirmedpromptlytopreventdryingout.Large,establishedcontainer-grownplantscanbehandledlikewiseonceremovedfromthepotsor,inthecase of younger plants, root cutting material can be removedwhenthegrowingmediumhasbeengentlyshakenawaytoexposeyoungroots.

Stock plants for layering and stoolingHigh-qualitystockplantsgrownonwell-drained,fertilelandwithashelteredaspect,freeofperennialweeds,areessential to produce the requisite succession of strong, youngshootssuitableforlayeringandstooling.Inthecaseoflayering,plantsshouldbewellestablishedandwidelyspaced,usuallysome2–2.5m,inrowsset3mapart,toenablethenecessarypeggingdownofshoots.Given the long-term nature of stool beds, only high-qualitystockplantsofknownhealthstatusshouldbeused.In-rowspacingvarieswiththevigourofthespeciesgrownandthenumberofshootsproducedby aparticularsubjectwheninfullproductionbutwillgenerallybearound25–40cm.Typically,rowsarespacedat1mtofacilitateearthingup.

Stock bed production periodsThe productive life of a stock bed is usually 10–15 years (withregularpruning),dependingonspeciesandhowwellorotherwiseithasbeenlookedafter.Sometreespecies including Malus, Platanus, Prunus, Quercus and Tilia produce juvenile material for longer if pruned regularly,whileheatheroralpinestockplantsmayneedreplacingeverythreetofiveyears.Beginrenewalplantingsatleastthreeyearsinadvanceofstockreplacementtoensurecontinuityofsupply.Container-grownstockplantsareusuallykeptforoneortwoseasons,perhapslongerwithsupplementarynutrition,beforebeinggrownonassaleablespecimenplants.


Table5.Examplemanagem

entp

rogram

meforH

NSstockbe

ds

Mon

thPl

antin

gPr

unin

gC

rop

prot

ectio

nC

ultu

ral

Har

vest

ing

January

Con

ifers

, eve

rgre

ens

and

deci

duou

s sp

ecie

s

Fruita

ndornam

entalH

NS

forb

udwoo

dprod

uction

andhardwoo

dcutting

s

Review

and

upd

atespray

prog

ram

mes

for p

est a

nd

dise

ase

cont

rol

Che

ck s

tock

pla

nts

unde

r pr

otec

tion

for B

otry

tis

Review

and

upd

ate

pl

antin

g pl

an

Root

cut

tings

(her

bace

ous)

Hardw

oodcutting

s(shrub

s,fruitstocks

andHNS)

Sem

i-rip

e cu

tting

s (c

onife

rs)

Softw

oodcutting

sfro

mfo

rced

stock

plan

ts u

nder

pro

tect

ion

(dec

iduo

us a

nd

ever

gree

n sh

rubs

)Sc

ionwoo

dforb

enchgrafting

(e.g.B

etul

a, C

arpi

nus)

Febr

uary

Con

ifers

, eve

rgre

ens,

ro

ses

and

deci

duou

s sp

ecie

s

Fruita

ndornam

entalH

NS

forb

udwoo

dprod

uctionfor

hardwoo

dcutting

s

Review

and

upd

atespray

prog

ram

mes

for p

est a

nd

dise

ase

cont

rol

Che

ck s

tock

pla

nts

unde

r pr

otec

tion

for B

otry

tis

Che

ck la

bels

, tre

e tie

s

and

stak

es

Root

cut

tings

(her

bace

ous)

Hardw

oodcutting

s(fruitstocksandHNS)

Sem

i-rip

e cu

tting

s (c

onife

rs)

Softw

oodcutting

sfro

mfo

rced

stock

plan

ts u

nder

pro

tect

ion

(dec

iduo

us a

nd

ever

gree

n sh

rubs

)Sc

ionwoo

dforb

enchgrafting

(e.g.B

etul

a, C

arpi

nus)

Mar

ch

Con

ifers

, eve

rgre

ens,

ro

ses

and

deci

duou

s sp

ecie

sH

erba

ceou

s pe

renn

ials

Stoo

lstockbed

s(e.g.

Cor

nus,

Hyd

rang

ea,

Hyp

eric

um, P

oten

tilla

, Sa

lix, S

enec

io, S

pira

ea

and

Syrin

ga)

Prun

e Be

rber

is, B

uddl

eia,

D

eutz

ia, F

orsy

thia

, Ph

ilade

lphu

s, W

eige

la

and

sim

ilar

Renewalpruneasrequ

ired

(e.g.C

amel

lia, V

ibur

num

an

d Ile

x)Pr

une

heat

hers

Prun

e st

ock

hedg

es fo

r hardwoo

dcutting

produ

ction

(shr

ubs

and

trees

)

Appl

y re

sidu

al h

erbi

cide

s fro

mM

archonw

ardsfo

rspringandsummerweed

cont

rol o

n es

tabl

ishe

d st

ock

beds

onl

yC

heck

and

trea

t Mal

us

for s

cab

Che

ck a

nd tr

eat a

ll st

ock

for

aphids,M

archonw

ards

Appl

y fe

rtilis

er to

p-dr

essi

ng

(und

erta

ke s

oil a

naly

ses

ever

y th

ree

year

s)

Scionwoo

dforfi

eldgrafting

(d

ecid

uous

shr

ubs

and

trees

)Se

mi-r

ipe

cutti

ngs

(con

ifers

)So

ftwoo

dcutting

sfro

mfo

rced

stock

plan

ts u

nder

pro

tect

ion

(dec

iduo

us

and

ever

gree

n sh

rubs

)Leaf-bud

cuttings(e.g.C

amel

lia,

Mah

oniaetc.)

Root

cut

tings

(her

bace

ous)

Her

bace

ous

basa

l cut

tings

Earlysoftwoo

dcutting

sforced

un

der p

rote

ctio

nSc

ionwoo

dforb

enchgrafting

(con

ifers)

Seed

harvesting,M

archonw

ards


Mon

thPl

antin

gPr

unin

gC

rop

prot

ectio

nC

ultu

ral

Har

vest

ing

April

Con

ifers

, eve

rgre

ens

and

deci

duou

s sp

ecie

sH

erba

ceou

s pe

renn

ials

Broa

d-le

af e

verg

reen

s fo

r cu

tting

pro

duct

ion

Che

ck a

nd tr

eat f

or

two-spottedspiderm

ites,

Aprilonw

ards,p

articularly

unde

rprotection(e.g.

Budd

leia

, Crin

oden

dron

, C

hois

ya a

nd E

uony

mus

)Check/treatforcaterpillar

damage,Aprilon

wards

(e.g.C

hois

ya, E

uony

mus

, Ph

otin

ia, c

onife

rs)

Use

irrig

atio

n to

mai

ntai

n vi

gour

dur

ing

dry

perio

ds

fromAprilon

wardsfo

rstool

beds

and

laye

r bed

sM

ulch

app

licat

ion

for

springweedcontrol

Softw

oodcutting

s(e.g.A

cer,

Azal

ea,

Cot

inus

, Exo

chor

da, H

yper

icum

, M

agno

lia, S

pira

ea, S

yrin

ga),

idea

lly

prop

agated

info

gwithbasalheat

Her

bace

ous

basa

l cut

tings

May

Her

bace

ous

pere

nnia

ls,

com

plet

e pl

antin

gBr

oad-

leaf

eve

rgre

ens

for

cutti

ng p

rodu

ctio

n

As A

pril

Checkand

treatforpow

dery

mildew

(e.g.E

uony

mus

, H

ydra

ngea

, Lon

icer

a,

Mal

us, P

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Clonal selection and plant healthVariabilityinrooting,growthandfloweringcharacteristicsbetweendifferentclones(thevegetativelyproduced progeny of a single plant) of a particular plant isacommonprobleminHNSproduction.Itinfluencespropagation performance and, ultimately, saleability, particularlywhereclonesarehighlyvariableandnot truetotype.Forthisreason,superiorclonesareoftenselected from stock and bulked up to provide a reliable sourceofpropagationmaterialthatistruetotype.

HNS clonal selection schemeVariationwithinHNSformedthebackdroptoahardyornamentals scheme that began in 1976 at the former LongAshtonResearchStation,progressedtoNIABEMR(1984)andceasedin1991atHRIEfford.OfparticularconcernwasthatthesameHNSsubjectssuppliedbydifferentnurseriesperformeddifferently,dependinguponthesource.Theprincipalobjectivesoftheschemewereto:

• Examine the causes of variability

• Assess, identify and select a clone or clones that weretruetotype,reliableinperformanceand,ifpossible, an improvement on those in commercial practice at the time

• Identifyplantsshowingnovelandinterestingvariationthatwouldbeofvalueinmaintaininggeneticdiversitywithinthespeciesorcultivar

Threemaincausesofvariabilitywereidentified:incorrect naming, genetic variation and infection by virusesorotherdiseasepathogens.Duringthecourseofthescheme,manysuperiorcloneswereidentified andreleasedtotheindustry.Someofthese,denoted bytheEMorLAsuffix,stillexistandareworth sourcingforstockplants.

Dutch Plant Health and Inspection Service (NAKTUINBOUW formerly NAKB)Thisschemewasderivedfromagradualmergerofseveral plant health inspection services, including the former Inspection Service for Arboriculture (NAKB,establishedin1943)and‘NederlandseAlgemeneKeuringsdienstvoorBloemisterij-enBoomkwekerijgewassen’–InspectionServiceforFloricultureandArboriculture(NAKTUINBOUW)whichis a foundation run under the auspices of the Dutch MinistryofAgriculture.The scheme functions along similar lines to the former NuclearStockAssociation(NSA)intheUKanditsprincipalremitistopromoteandfacilitatethegrowingofhealthy,high-qualitytruetotypeplantmaterial.Itsinspectionworkcoverstopandsoftfruitspecies(most notably, Malus and Prunus) and ornamental trees (including: Acer, Betula, Crataegus, Fagus, Fraxinus, Tilia and Quercus) and conifers (particularly, those grownintheNetherlandsfortimberproduction).Nurseryinspectionsforapprovalandcertificationcoveradministration, plant production, plant management

and phytosanitation, and include stock plant material, nurserypropagationmaterialandplantsgrownonforsale.SuccessfulnurseriescanusetheNAKTUINBOUWqualityinspectionmarkontheirmaterial.TheschemefosterscloselinksbetweentheDutchPlant Health Service and the research expertise at Wageningen,fromwherevirus-freeandtestedclonalmaterialisderived.ThismaterialispropagatedandmaintainedbyNAKTUINBOUWandeachyearnewvirus-freestockisaddedtothecollection.Ensuringgrowershaveaccesstohealthyplantmaterialthat is true to type is one of the principal aims of the inspection service and, in order to facilitate this, the organisationmanagesitsownstockplantmaterial,whichissoldtogrowersondemand.UKgrowersoftensourceNAKTUINBOUWcertificatedmaterialforplantpropagation,particularlybudandscionwoodforfruitandornamentaltreepropagation.

RootstocksRootstocks,ontowhichabudorscionisgraftedorbuddedtoformtheheadormainbranchframeworkofthetreearecommonlyusedinnurserystockproduction.Withornamentalsubjects,thiswillusuallybebecauseof their greater vigour or rooting potential although, withfruittreepropagation,itcanalsobeonaccountoftheirgrowthcontrolcharacteristics,asinthecaseofdwarfingrootstocksrequiredfortheproductionofsmaller,morecompacttreessuitableforretailsales.

Seedling rootstocksRootstocksgrownfortheproductionofwoodyornamentals, can be raised successfully and economically from seed, normally drilled in outdoor seedbedstoproduceoneortwo-yearseedlingsforbuddingorgraftingonto.Whilerelativelycheap,themaindrawbackofseedlingrootstocksistheirinherentvariability,leadingtounevengrowthfollowingbuddingorgrafting.Hence,onlystrong,high-qualityrootstocksgrownfromreliableseedsourcesofknownhealthstatusandprovenanceshouldbeused.

Clonal rootstocksClonal rootstocks are propagated vegetatively, usually fromhardwoodcuttingsand,whilemorecostlytoproduce than seed raised material, have the advantage of greater uniformity, provided that evenly graded, good quality propagation material taken from clonal stock plantsisused.Fruit tree rootstocks for budding or grafting are usually propagatedbyhardwoodcuttingsduringthewinterperiodwhentheyareleaflessanddormant,althoughtheycanalsoberaisedfromstoolbedsandlayering.

MicropropagationMicropropagation can be used for raising rootstock material,usuallyinrespectofsubjectsthataredifficultorslowtorootbyconventionalmeansorwhererapidbulkingupisrequired.


StoolingTheunderlyingprincipleofthistechniqueisthatwhenyoung shoots are placed in darkness, for example, by having soil earthed up over part of them, they become blanched and produce young, adventitious roots, at whichpointtheyareharvestedfromthemotherplantandgrownonforbuddingorgraftingortoformyoungnurserytrees.Itdiffersfrometiolation,wherebyshootsareactuallygrownindarkness.While probably the oldest form of vegetative propagation and one of the most reliable, the labour-intensive nature of stool bed management has ledtoitbeingsupersededbyother,morecost-effectivetechniquesforpropagationofrootstocks.

LayeringRootstocks, particularly those intended for fruit tree production can also be propagated by a form of layering knownasetiolationlayering,wherebyyoungmotherplantsareplantedatanangleof45°,peggeddownandcoveredwithfinesoilbeforebudbreaksuchthatyounglateral shoots are produced in darkness and become etiolated.Theemergedshootsarethen‘earthedup’twoor three times, starting in late spring before the rooted shootsareharvestedduringthewinter,linedoutandgrownonforbuddingorfieldgrafting.Unrootedshootsarepeggeddownagaintoproducerootstockmaterialforthefollowingyear.Once favoured for the production of cherry rootstocks and,occasionally,walnutandmulberryplants,thissystemisalsolabourintensiveanddifficulttomechanise,andnolongereconomiconacommercialscale.Other types of layering are still practiced for the raising ofarangeofwoodyornamentalsubjects.

Collection and storage of vegetative propagation materialCollectionThecollectionofcuttingsandgraftwoodshouldbedoneinacarefullycoordinatedandstructuredwaysoastolinkefficientlywithsubsequentstorage,preparationandinsertion.Collectedmaterialshouldnotbeleftunattendedotherwiseitwillquicklydeteriorate.Therearesomebasic,butimportant,rulestofollowwithbags and labels used for the collection and storage of propagation material, notably:

• Usestrong,whitepolythenebagsorhessiansackswhencollectingcuttings.Avoidusingclearorblackpolythene bags as they absorb more heat and the cuttingswillquicklydeteriorate,especiallyinsummer

• Dampenthebagslightlywithplainwaterontheinside to help keep cutting material moist and turgid, especiallyinspringtosummer.Don’toverdothis,otherwisesoftcuttingmaterialwillquicklyrot

• Ensure each bag is clearly labelled using a waterproofmarkerpen

• Write clearly and ensure the material is correctly labelled,withthenameoftheplant,thedatecollected and the source of the material

• Ensurethelabelsarestrong,waterproofandclearlyvisibleand,inthecaseoftie-onlabels,arewellsecured to the bag

• Ensurethelabelsfollowthepropagationmaterialthrough the preparation and insertion stages so the plantmaterialcanbequicklyandcorrectlyidentified

• Onceinserted,useplastic,stickinlabelswitheachtrayorbatchofcuttingsorseed;writethefullnameof the subject on the label, the source and the date of insertion

Generally, cuttings taken from strong, juvenile, actively growingshootswillrootquickerandbetterandproducestrongerfinishedplantsthanmaterialtakenfromlessactiveshoots.Verysoftgrowingpointswithhighnitrogenlevelsarelesslikelytorootwell.InworkatNIABEMR,thetimingandfrequencyofharvestingaffectedcuttingproductivity.Earlyseasonharvesting(earlyJune)andrepeatharvestingasnewshoots reached the requisite size led to a greater number of cuttings compared to leaving cutting materialonthestockplantsuntillater(lateJulyormid-September).Theearlyseasonremovalofcuttingmaterialoftenstimulatednewshootgrowththatcouldbeharvestedlater.Whencollectingcuttingmaterialinthefield,theremovalof branches or larger shoots from stock plants and the subsequent preparation of cuttings from these on return tothepropagationareaisusuallymoreefficientthanremovinglargenumbersofsmallcuttingsatsource.

.Removing larger shoots from stock plants and preparing cuttings fromtheseisefficientandhelpskeepsoftmaterialfresh


Spring and summer cutting material should be collected intheearlymorningwhenconditionsarecoolandfresh.It should be kept out of direct sunlight and transferred tocoldstoragepromptly.Soakingcuttingsorcuttingmaterialinwaterforprolongedperiodsinanefforttokeep them fresh is not advisable, as such material can quicklydeteriorate;controlledtemperaturestorageismuchbetter.Whilelessperishablethansoftwoodandsemi-ripecutting material, the collection and handling of hardwoodcuttingsshouldbeundertakeninasimilarway,inthatthematerialshouldbebaggedanddealtwithpromptlyandkeptawayfromdirectsunlightor heatandextremesofmoisture.

StorageWhen handling propagation material, especially softwoodsummercuttings,whichcandeterioratequickly,theemphasismustalwaysbeonworkingquicklyandefficiently,tokeepmaterialin optimumcondition.Water loss from unrooted leafy cuttings must be minimised so they remain fresh, turgid and in optimum conditionforrooting.Materialshouldbehandledquicklyandkeptinacool,shadedlocationawayfromdirectsunlight.Materialshouldalsobehandledcarefullyas damaged tissue may become an infection site for disease, notably Botrytis;softcuttingsespeciallyareeasilybruised.Plasticboxeslinedwiththingaugewhitepolythene canbeusedtokeepcuttingmaterialcoolandmoist.

winter.Plasticboxeslinedwiththingaugewhitepolythenekeepcuttingmaterial cool and moist

Coldtemperaturestoragetoremove‘fieldheat’fromsoft leafy cutting material maintains cutting quality and improvesrootingpotential.Usually,twohoursstorageat1–3°Cfollowingcollectionwillrestoreturgidityandensure cuttings are fresh before insertion, although mostspeciescanbestoredinthiswayforseveraldays.Storageperiodsshouldbekepttoaminimumwherepossible.Refrigerationunitscanbeusedforsmallquantitiesofmaterial.Suchfacilitiesneednotbeexpensive;forsmallpropagationunits,largecapacitydomesticfridgesoftensufficeandlargerenterprisesmaywellfindthatsimplelow-costrefrigerationunits areadequate.Material should be transferred promptly from cold stores to propagation beds and should be labelled accurately anddatedwheninserted.

Preparation and handling of cuttingsWork areasWork areas for propagation tasks, notably the preparation and insertion of cutting material, should be cleanandtidy,organisedandfreeofcluttersothatworkcanproceedquicklyandefficiently.Allmaterialsneedto be close to hand, for example, cutting material for preparation, tools, trays and rooting hormone and an exit route for inserted material to be removed promptly tothepropagationstructure.Goodlightisessentialandworktopsshouldhaveasmooth,wipecleansurfacethatcanbedisinfectedregularly.Theworkareashouldalsohavealogicalflowtoitforefficientworkingtomaximisethroughputs.Staffshouldhavesufficientspacetoworkandnotbecramped.Seatingshouldbeadjustableandideallywheeledtoenablestafftomovefreelyandworkquickly.Benchesshouldbeofaconvenientheightforstafftoworkatcomfortablywithoutstretchingorstruggling,whichinducefatigueandreduceproductivity.

winter.Workshouldflowsmoothlywithallmaterialsclosetohand


Team workingItisimportanttoworkwellasateam,particularlywhenhandlinglargevolumesofpropagationmaterialduringpeakperiods.Separateoutthekeytaskssuchas collection, preparation, insertion and transfer to thepropagationstructuresbutensurethesearewellintegratedtoenableworktoproceedsmoothly withminimumdisruption.Usually,themostefficientapproachisforsomeone to‘service’thoseteammemberstaskedwithpreparingand sticking the material (collection is usually dealt withseparately).Thispersonshouldensureeverythingruns smoothly and the team doesn’t run short of tools, cuttingmaterial,trays,rootinghormone,etc.Itisalsotheir responsibility to ensure that cutting material is correctlylabelledandtakenawaypromptly,toensurethatconveyorsdon’tbecomebackedup.Theteamleaderorservicer(theyareoften,butnotalways,thesame person) should also check outputs to ensure workisprogressingasrequiredandisqualitycontrolled.

Managing staff and the workplace environmentItisimportanttorotatestaffperiodicallytoavoidfatigueand so maintain productivity, especially during busy periods;asaguide,trytodothisatleastonceaday so that team members don’t spend all day, every day, repeatingthesametask.Manynurseriesuseseasonal,part-timestaffandemployshiftworkingforhighlyrepetitiveworksuchasthis.Thisusuallyworkswell,providedstaffaresupervisedandcorrectlytrained.Staffarealwaysmoreproductivewhentheirworkingenvironment is safe and comfortable, so ensure there is adequate shade and ventilation during bright, hot periods and background heat is provided whenrequired.

Give careful thought to the location and layout of the workarea;oftenthisiscentrallylocatedonsitebutneedstobenearthepropagationstructure;theyarenotalwaysthesamething,leadingtoexcessivehandlingtimeandcosts.Onlargeormulti-siteoperations,considermobilisingtheworksoitcanbelocatedclosetothepropagationstructuretominimisetransporttime.Considerusingmobileworkareassuchasportakabinsorcaravans,whichcanbeadaptedandmovedasworkproceedsandlocationschange.

Selecting cutting materialWhen selecting cutting material, it is important to avoid usingverysofttipgrowthwithhighlevelsofnitrogen asthematerialisunlikelytorootwellorgrowonto formstrong,satisfactoryplants.Theyarealsodifficult tomanageandkeepfresh.Similarly,olderwoodyportions of stem should be discarded as such material isslowtoroot.Weak,thinshootmaterialshouldalso beavoidedaswellasverythickportionsofstem.Thebestmaterialtouseisthatgrowninfulllight,whichhasadegreeofflexingbutismatureenoughtosnapcrisplywhenbentsharply.Often,strongsideshootsandlateral branches provide the best material and pruning out the leading shoots of shrubs, for example, helps to promote their development and the total number produced.Forhardwoodcuttings,well-ripenedwoodofmoderate size and vigour should be used to ensure the cuttings have adequate food reserves in the form of carbohydrates, to sustain root development and initialshootgrowth.Shoottipsareusuallydiscarded;centralandbasalstemsectionsmakethebestcuttings.

Awell-organisedteamworkinginclean,well-litconditionsmaximisesoutput


Handling cuttingsMostcuttingsarenowrooteddirectlyintopotsorplugtrays to ease and speed up handling and reduce root disturbance, leading to quicker establishment once transplantedorpottedon.Thepreparationandinsertionofcuttingscanbetime-consumingandlaboriouswork.Itcanalsobeexpensiveandworkshouldproceedquicklybutbeunhurried,withdueregardto maintainingcuttingquality.

winter.Wheninsertingcuttings,traysshouldbetiltedgentlyforwardtoease and speed up handling

ADASstudiesduringthe1980sidentifiedseverallabour‘bottlenecks’inthepreparationofcuttings,whichled to the development of improved or preferred methods of handling, capable of up to 50% savings in production time.Whilesecateurswerestillused,thetraditionalknifewasreplacedbyascalpel-likedisposabletool thatwascheaper,saferandeasiertouse.

Theworkstudyprinciplesandbenefitsremaintruetodayandcanbeadaptedtocurrentpractice.Tweezers,for example, can be (and are) used for the handling and inserting of very small, soft cuttings into plug trays andlightweightscissorsorsnipsarepopularwithstaffpreparingcuttingmaterialforinsertion.Advantages of the ADAS system include:

• Easy to teach and learn

• Muchquickerthantraditionaltechniqueswherecuttingsmaybepickedupandputdownseveraltimes, therefore increasing productivity

• Reduced handling means less bruising and damage to cutting material and, as a consequence, less disease problems

• Quicker throughput limits moisture stress of cuttings, especially soft, leafy material in the summer

• Opportunitiesforstafftoearnmoreandmanagers tostimulateproductivitybybonusorpiece-work

• Easiermonitoringofworkqualityandoutputsbyteam leaders or managers

ThetechniquesweredevelopedbyformerADASAdvisorBrianMorgan.Theycanbeadaptedfor batch preparation and insertion of easy to handle cuttings(e.g.semi-ripeconifercuttingsandshrubspropagated by tip cuttings such as Buddleia, Cotoneaster and Hypericum)orsingle/doublepreparationofmoredifficultmaterialsuchaslargeleavedcuttings(e.g.Rhododendron), internodal cuttings (e.g.Clematis)orverysmallcuttings(e.g.heathers).Figure 5 summarises the ADAS methodology for batch preparation and insertion, and Figure 6 the methodology forthepreparationandinsertionofoneortwocuttings atatime.Commontoeachmethodistheinclusionofwoundingandhormonetreatmentofcuttings.Staffmembers areseatedandworkfromabenchwithtraysgentlytippedtowardsthemforquickerandeasierinsertion ofcuttings.

Lightweightscissorsor‘snips’areidealwhenpreparingsoftcuttingmaterial


Figure5.Batchpreparationandplantingofcuttings

Pick up another cutting and repeat the process

As they are prepared, gather the cuttings in one hand, keeping the butt ends together

Continue until a handful of cuttings are prepared

Dipthebuttendsofthegatheredcuttingsinapotofhormone.Flickoffsurplushormone

Dispense one cutting at a time to the free hand, insert the cutting into the propagationtray,startingatatopcorner.Workdiagonallyacrossthetray

Pick up a cutting in one hand, transfer it to the other

Semi-ripe cutting e.g.conifers

Remove cuttings from branches/stockmaterial withsecateursanddrop cuttings onto a table in a pile of the selected grade

Stripoffbasalleavesbydrawingfingersdownthestem

Cutbaseofstemwithknife

Tip cuttings e.g.Hypericum

Large thorny cuttings e.g.Berberis

Remove cuttings from branches/stockmaterial withsecateursanddrop cuttings onto a table in a pile of the selected grade

Selectionofcuttingmaterials.Cuttings collected individually fromstockplantwithaknife

Cutstembelowanode, removebottomtwoleaves

If necessary, cut top leaves inhalfwithyourknife

(Wearing a glove on one hand) cutoff,belowanode,requiredlengthofcutting.Theendcan

be dropped onto the pile of cutting material

Cutoffunwantedstemabove top node

Cutoffbottomthorns; pulloffleavesifnecessary

Woundthestemwithsecateurs

10–15 cuttings 15 cuttings

5–8 cuttings


Outputs and monitoring of workTable 6 provides reference points for trainers and supervisors, and incorporates the average of the best25%ofstaffingoodconditions,thetypical workerundertypicalconditionsandtheaverage oftheworst25%ofworkersinpoorconditions.Table6.Timesforpreparationandinsertionofcuttings

Type of plant material

Time (minutes per 1,000 cuttings)

Good Typical Poor

Hypericum species 50 60 100

Cupressus species 70 90 140

Berberis species (gloved hand) 150 280 380

Rhododendron species 180 270 420

Thesefigurescanbeusedasbenchmarkswhensettingtargetsforstaffandmonitoringtheiroutputs.However,takeaccountofworkconditionsandthetypeofcuttingmaterialinvolved.Thebetterandmoreorganisedtheworkplace,thegreatertheoutput.Record rates on a daily basis and separate out preparation and insertion from the collection of cuttingmaterial;thetwotasksareinvariablydoneatdifferenttimesbydifferentstaff.Keeprecordsandtheinterpretationofdataassimpleaspossible.Use colour labels in trays to code and monitor individualssothatproductivityandqualityofwork canbemonitored.

Lean managementLean management is a set of techniques that can be usedtohelpreducecostsandaddvaluetobusinesses.It does this by improving productivity and customer servicelevels,reducingplantlosses,removingwastage

Large-leaved cuttings e.g.Rhododendron

Cutstemsbelowanode. Cutofflowerleaves.Wound

baseofstem.Cuttop leaves as necessary

Dip individual cuttings inrootinghormone.Plantin

propagation tray

Eachmatureleafwillyieldonecutting.Preparecuttingsbycutting the stem of the stock

material into pieces, forming piles ofwasteandcuttingsonthetable

Use thumbnail of one hand tobreak1.5–2cmofstemfromstock plant material held in the

other hand

Removethelowerleavesbydrawingfingersdownthestem

Pickuptwocuttings, one in each hand

Dip both cuttings inrootinghormone.Insert

cuttings into propagation tray, startinginthemiddleoftherow

farthestawayfromyou.

Insert the cutting, in a propagation traywithpre-madeholes;startat

therowfarthestaway

Internodal climber cuttings e.g.Clematis

Very small cuttings e.g.Erica

Cuttings collected individually fromstockplantswithsecateurs

Collect small branches of cutting material

Pick up a cutting in one hand, transfer it to the other

Figure6.Preparationandplantingofoneortwocuttingsatatime


andcuttingleadtimes.IthasbeensuccessfullyappliedintheUKtomanyhorticulturalbusinesses,includingproductionnurseries,gardencentresandlandscapers.Nurserystudieshavemainlyconsideredorderdespatchactivitiesandhowproductivitycanbeimprovedwhilecopingwiththeusuallylargefluctuationsinseasonaldemand.Thecollection,preparationandinsertionofcuttings, direct seeding into modules and subsequent transplantingalsoinvolvesignificantamountsofmaterialshandlingandstafftime.Assuch,theyarecostlyandlendthemselveswelltotheprocessmappingandimprovementprinciplesofleanmanagement.SeveralHNSbusinesseshavesuccessfullyappliedtheprinciplesofleanmanagementtocriticallyreviewandsignificantlyimprovetheirpropagationpractices.Thereis clearly scope to apply the principles and practices of leanmanagementmorewidely,focusingonthespecifictasksmentionedpreviously.Itcouldalsobeusefullyapplied to other tasks, notably liner potting, budding andgrafting.The HTA (the‑hta.org.uk) currently runs a bespoke service on lean management for their members, in partnershipwithNeilFedden(fedden‑usp.co.uk), one oftheUK’sleadingauthoritiesontheapplicationofleantoolsandtechniques.

Wounding, leaf stripping and trimming of cuttingsWoundingWounding the basal stem area of cuttings such thatthehardenedouterlayerofepidermalwoodispartlyremovedtoexposethecambiumisknowntostimulaterootinginmanyHNSsubjects.Often,onlyalightscrapingorwoundingisnecessaryasinthepropagation of soft evergreen species such as Azalea.Withwell-ripenedorhardwoodcuttingmaterialaheavierwoundisrequired,usuallyasaprecursorto theapplicationofarootinghormoneproduct.Asimplescrapingactionissometimesusedwithcuttingswhenitisdifficulttoeitherremoveasliceofstemtissueortopenetrateintothestemwithaknifeblade,forexample,withverysmallcuttingssuchasheathers.Infact,withnarrowleavedevergreenspeciessuchasheathersandmanyconifers,thewoundingeffectofstrippingthelowerleavesorlateralshoots to enable their insertion into the rooting medium often createsanadequatewoundingeffect.Woundingmay,however,increasebasalrottingandsorequirescare andattention.Wounding increases the quantity and quality of roots asnewsitesforrootinitiationaretriggeredwhen basalstemtissueisexposed.Itenhancestheuptakeandeffectofappliedrootinghormonesanditalsoincreaseswateruptakefromtherootingmedium,important to maintain the turgidity of large leaved cuttings such as Rhododendron, Magnolia and evergreen Prunusvarieties.

Wounding also encourages roots to develop further upthestem,offeringausefulsafeguardifbasalrootsdeteriorateandrotoff.Physiology of woundingTherootinitiatingeffectofwoundingisdueprimarily toitstimulatingaproliferationofnewrootinitialsand inturnmorenewrootsfromthevascularstemtissue. Italsotriggersthedevelopmentofnewparenchymacells(‘callus’),aknownprecursortorootinitiation.Thephysical removal of a portion of harder basal stem tissue isalsothoughttoenablegreaterwaterabsorption,easier penetration of applied rooting hormones and, in some subjects, the removal of physical barriers to root emergence,suchasthickwalledstemcells.Inatleastsomesubjects,itisalsolikelythatwoundingfacilitatesthereleaseofrootpromotingstimuli.Usually,themorecommonslicewoundisaround2cmlongandinvolvesremovingshallowsliversoftissuefromthebaseofthestem.Normally,thisisdonewitha sharp knife although the more practiced propagators are able to use the blade of a secateur for this, for example,withlargeevergreencuttingssuchas Prunus laurocerasus.Often,asingleslicewoundmadetoonesideofthebasalareawillsufficebut,forhardwoodormoredifficulttorootsubjects,bothsidesmaybewounded.Thedepthofthewounddependslargelyonthespecies,theextentoflignificationor‘ripeness’ofthewood,thethicknessofthebarkandtheoverallstemdiameter.Insomecases,aheavierslicewoundisrequired in order to penetrate the bark and expose cambialtissue.However,thismustbedonewithgreatcareotherwisethecuttingwillbedamaged.Shallowwoundingshouldalsoexposecambialtissuebutisgenerallymoreeffectivethanheavywounding,whereitcanbeused;itispossiblethatshallowwoundingproportionately exposes more cortex and phloem than xylem(wood)tissueascomparedtoheavywounding,anditisthistissueratherthanxylemfromwhichnewrootsariseincuttingsofwoodyHNSsubjects.Tobeeffectiveandminimisedamagetothestemofthecutting,woundingmustbedonequicklyandpreciselyusingasharpknifeorblade.Italsorequirespatienceandpracticetodoitcorrectly.

Types of woundingSlice woundingSingleslicewoundingisthemostcommontechniqueand useful for semi-ripe cuttings of subjects such as Elaeagnus, Garrya, Ilex, Osmanthus, Prunus (evergreen species) Pyracantha and Viburnum (evergreen species), forexample.Thedoubleslicewoundcanbeusedforsubjectsthatdo not root readily around the stem, such as some of the Rhododendron species,whichoftenrootononesideandsoaremoreliabletodamagewhentransplanted.


winter.AsingleslicewoundissuitableforawiderangeofsubjectsandthemostcommontypeofwoundusedwithHNS

Thereisalsoathirdtypeofslicewoundknownasthemodifiedslicewound,inwhichthecutismadefurtherupthestem,leavingthebottom1cmunwounded.Although more common in America, this technique has provedsuccessfulforevergreenhardwoodcuttingsinwhichstemrotorpoorrootingoccursatthebaseof thecutting,especiallywhenthereisthelikelihoodof therootingmediumbecomingtoowet.Incision woundWiththistypeofwound,notissueisremovedbutthetipofasharpknifeisdrawndownthebasal2–3cmofstemsothatitpenetratestothexylemwood.Insomecases,uptothreesuchwoundsaremadeonthecutting.Thistechnique is less common and not easy to do unless thecuttingissupported,forexample,helddownon aflatsurfacewithonehandwhilemakingthewound.Incisionwoundingisusefulwiththinnerstemcuttings,for example, of conifers such as Cupressus and Juniperus,whereslicewoundingismoredifficulttodo.

winter.Incisionwoundingislesscommonbutusefulforthin stemmed cuttings

Anatomicalstudieshaveshownthatthecallusthatdevelopsfromincisionwoundingisderivedmostlyfromthecortex(centralpith)andthatnewcambiumdevelopswithinthiscallustissue,adjacenttotheoriginalcambium,soineffectformingacambial‘bridge’.Thiscallusislaiddownasanoutwardpointingprotuberanceanditisatthispointthatanewrootinitiatesanddevelops.This‘bridge’alsodevelopsfollowingslicewounding.

Split woundThiswoundinvolvessplittingthebasalstemarearatherthansurfacewoundingit.Itissometimesdonewhenpreparinghardwoodcuttings,forexample,offruittree rootstocks but requires care to avoid damaging thecutting.Italsoworkswellforsummercuttingsof Edgeworthia chrysantha.Typically,suchsplitsarearound1cmdeep.

winter.Splitwoundingcanbemoreeffectiveatpromotingrooting insomeHNSsubjects

WorkatNIABEMRwithdormantwintercuttingsofapplerootstocks(M26)inheatedbinsshowedthatincisionwoundingwasmoreeffectiveinpromotingrootingthanslicewoundingandthatsplitwounding wasbetterstill.GoodresultswerealsoevidentwithwintercuttingsofAcer platanoides ‘CrimsonKing’andCastanea sativa.Splitwoundingenablesmorecallustodevelopthanincisionwoundingandalineoftwooutwardpointingprotuberanceslaterdifferentiatetoprovideasourceofpotentialrootsratherthantheusualsinglelinewithincisionwounding.ThismayexplainwhysplitwoundingcanbemoreeffectiveatpromotingrootinginsomeHNSsubjectsthanincisionorslicewounding.Thegreateruptakeofrootinghormonefromsplitwoundingoverincisionwoundingmaybeanotherfactor.

Leaf removalTraditionally, basal leaves are removed from cuttings to prevent their deterioration on the rooting medium, whichcantriggerplantpathogenicinfectionssuchas Botrytis.Theremovalofthelowerleavesisalsofrequently necessary to enable secure insertion of the cutting,forexample,withheavy,large-leavedevergreensubjectswithstrongleavesandleafpetiolessuchasCamellia, Elaeagnus, Ilex, Mahonia, Osmanthus and Skimmia.Thisisespeciallysoifthechosenmediumisverylightweight,forexample,a50:50peat-perlitemix.Usually, basal leaf removal also enables more cuttings tobeinsertedpertray.Timespentremovingleavescan,however,besignificant,particularlywhenhandlinglargenumbersofcuttings.WorkundertakenatMerristWoodCollegetoinvestigateleafremovalwitharangeofspecies


to assess its necessity, found that only one subject (Ceanothus) from 17 subjects tested during the SeptembertoMayperiodwereseriouslyaffected by Botrytis whenbasalleaveswereleftintact.Another reason often given for the removal of basal leavesisthatnewrootsarisemorereadilyfromthewoundscreatedwhentheyarepulledaway,althoughthesamestudyalsofoundthatmanyHNSsubjectsrootedreadilyfromthebaseofthecutting.Thestudyalso highlighted that some subjects such as heathers and Viburnum tinus, whichnormallyrootfromnodesratherthanstembases,rootedbetterwhenthelowerleaveswereleftintact,possiblybecauseofthebetteraerationaroundthebasalstemareawithintherootingmedium.Inthesametrial,Hebe rakaiensis rooted more readilyfromleaflessnodes(ratherthanwhentheleaveswereleftintact)thanfromthebasalareaofthecutting.It appears, therefore, that Hebe benefitsfromleafremoval.Table7summarisestheresultsofthiswork.Table7.EffectsofleafremovalonHNScuttings

HNS subjects not requiring leaf removal

HNS subjects requiring leaf

removal

Berberis (evergreen)

Berberis thunbergii ‘RoseGlow’

Ceanothus (in spring)

Conifers (various)

Elaeagnus pungens ‘Maculata’

Heathers

Hebe ‘Eversley Seedling’

Osmanthus heterophyllus

Pernettya mucronata

Pyracantha species

Spiraea x bumalda

Viburnum tinus

Ceanothus (in autumn)

Hebe rakaiensis

Skimmia japonica

Leaf trimmingReducing the size of the leaf blade is often done whenpropagatinglarge-leavedevergreensubjectssuch as evergreen Prunus, Rhododendron and sometimes Camellia,toreduceinitialwaterlossfromcuttings and to enable easier insertion into the rooting medium.Usually,italsoenablesmorecuttingstobeaccommodatedinatrayorpot.However,thecutsurface is susceptible to disease infection and care shouldbetakentoensurethecutsmadeareclean. A protectant fungicide treatment post-insertion is alsoadvisable.Researchwithfogpropagationindicatedthatuntrimmedcuttings may perform better than those that have their leaves cut, as they can photosynthesise better and are less likely to deteriorate under such high humidity environments.However,fogisamoresupportiveenvironmentthantraditionalmistorpolythenesystems.Where leaf trimming is undertaken, the aim should be to reduce the leaf blade by around one-third to one-halfinsize.

Rooting hormonesTo encourage quicker root initiation and more substantial root development, auxin-based root promoting hormone products are often applied to cuttings.Theseplantgrowthregulatorsareregistered as pesticides and require training in their storage, handlinganduse.Theyareparticularlyusefulfor semi-ripeandhardwoodcuttingmaterialandsubjectsknowntobedifficulttoroot.However,theyarenotusuallyessentialforsoftwoodcuttingmaterialoreasyrooting alpine or herbaceous subjects, although their usemayincreasetheuniformityandspeedofrooting.Literature mentions products based on the synthetic rootinghormoneIBA(indole-3-butyricacid)whichisnon-toxicandeffectiveoverawiderangeofHNSsubjectsandsomeuseofNAA(1-naphthaleneaceticacid) and the naturally occurring root hormone IAA (indole-3-aceticacid)but,currently,therearenoUKapprovedproductscontainingIAA.FollowingthecommercialwithdrawalofSeradixproducts(arangeofdifferentstrengthpowderIBAformulations) and Synergol (a ready to dilute hormone solutionbasedonIBAandNAA)during2011,Rhizoponproducts(basedonIBAorNAAandavailableas ready-usepowdersorwatersolubletabletsdissolvedforuseasdipsorsprays)arenowthestandardproductsapprovedforuse.

Powder preparationsThese are convenient and simple to use, requiring fresh cuts to be made to the base of the cuttings shortly before dipping the basal centimetre of stem into the powder,shakingofftheexcessandinsertingthecuttingintotherootingmedium.Itisimportantnottooverdosethecuttings,otherwisephytotoxicdamagemayoccuratthecuttingbase.Wherelargenumbersofcuttingsareinvolved, they can be bundled into a convenient number and dipped but it is important to ensure all the bases arelinedupevenly,otherwisesomecuttingswillreceivemorepowderthanothers.Cuttingswithlittleornonaturalmoistureshouldbemoistenedwithadampspongeortheendsdippedinwatertoaidretentionofthepowder.Cuttingsshould beinsertedimmediatelyfollowingtreatment.Cuttings should not be directly dipped into the bulk container of the product as this may lead to an early deteriorationofthepowderduetoitbecomingsoiledorcontaminatedbymoisture,fungiorbacteria.Instead,asufficientamountfortheworkinhandshouldbetransferred to a temporary container such as a plant potsaucerandanyleftoverdiscarded.Tomaximiseproductlongevity,containersshouldalwaysberesealedandstoredinacool,dryplacefollowingthecodeofpracticeonpesticideuse.When inserting treated cuttings into the rooting medium, it is good practice to use a dibber, as pushing the cuttings into the substrate may displace much of therootingpowder.


Concentrated solutions (‘quick dips’)Concentrated hormone solutions applied via a ‘quick dip’treatmentarealsousedintherootingofHNScuttings.Withthismethod,thelower0.5–5cmof stem (depending on the size and type of cutting) is dippedforfivesecondsinaconcentratedsolution ofhormone.‘Quickdips’aregenerallythoughttoofferquickerand more even rooting due to their rapid and easy absorptionintocambialtissuefromwhererootprimordia emerge and through the base and sides of thecutting.Takeparticularcaretoensurecuttingsare not dipped beyond the recommended period and appropriatedepth.Onlyusetheamountrequiredandavoid returning any surplus into any stock solution, otherwisecontaminationmayoccur.

Dilute solution soaking method (absorption method)This technique involves soaking the base of the cuttings in a dilute solution of rooting hormone preparation for severalhourspriortoinsertionintotherootingmedium.Theconcentrationtousewillvary,dependingontherootingpotentialofthespeciesinvolved.Currently,thisprocedureisnotwidelyusedintheUK,largelybecauseitisslowandrequiresconsiderabletime.All rooting hormone preparations should be used fresh wheneverpossibleandstoredincool,dryconditionsawayfromdirectsunlightandinclean,sealedcontainers.

Rhizopon product rangeThe Rhizopon range of products, originally developed intheNetherlandsbutusedworldwide,comprises ready-to-usepowderpreparationsandwatersolubletablets.Thelatteraredissolvedinwatertoformsolutions of varying concentrations for use either as absorption, total immersion (cutting dip), ‘quick dip’ or foliarspraytreatments.However,thislattermethodisnotcurrentlyapprovedintheUKafterthecuttingshavebeeninserted.Rootinghormonesareclassifiedaspesticidesandnotall of the products in the Rhizopon range have approval foruseintheUK,anumberhavealsobeenrevokedincludingproductsbasednaphthaleneaceticacid(NAA).Thosethatareapproved(atthetimeofwriting)are listedbelow:

• ChryzoponRose(0.1%IBA),whichistheequivalentof Seradix 1 and so suitable for softer cutting material

• ChryzotopGreen(0.25%IBA),whichissimilarinstrengthtoSeradix2(0.30%IBA)andsosuitable for general propagation of semi-ripe cuttings

• ChryzoplusGrey(0.8%IBA),whichistheequivalentof Seradix 3 and so more suitable for the propagation ofhardwoodcuttings

• RhizoponAAPowder1%(1.0%IBA)

• RhizoponAAPowder2%(2.0%IBA)

• RhizoponAATablets(50mgIBApertablet),whichare used to make liquid solutions of IBA at various strengths

Further information on Rhizopon products, including a useful ‘rooting guide’ to assist product selection can be found at rhizopon.com/en

Research with ‘quick dip’ solutions and powder preparations HRIEffordstudiesconsideredtheuseofliquid‘quickdips’andpowderedhormonepreparationsacrossarangeofHNSsubjects,includingRhododendron, some ofwhichareespeciallydifficulttoroot.Responsestoarangeofhormonetreatmentsvariedwithcultivar.Complementaryworkalsocomparedliquid‘quickdips’andpowderpreparationswithwinterstruckcuttingsforarangeofthemoredifficulttorootHNSspecies, including Camellia ‘Francie L’, Chamaecyparis lawsoniana ‘Lutea’, X Cupressocyparis leylandii, Elaeagnus pungens ‘Maculata’ and Mahonia bealei.Thisinitialworksuggestedthat1,250ppmofIBAcangiveequalorbetterresultswithsomespeciesthanthepreviousstandardof2,500ppm,althoughfurtherworkwouldberequiredtoconfirmthisoveranother,perhapspoorer,rootingseason.Asinearlierworkthough,the‘quick dips’ gave more consistent results overall than thepowderformulation.IncontinuedworkwithCamellia ‘Francie L’ and ‘E.G.Waterhouse’, Chamaecyparis lawsoniana ‘Columnaris Glauca’, Chamaecyparis lawsoniana ‘Lutea’, X Cupressocyparis leylandii, Elaeagnus pungens ‘Maculata’, Juniperus x media‘PfitzerianaAurea’, Mahonia japonica and Thuja occidentalis, IBA ‘quick dips’ gave similar or slightly improved rooting topowders(0.8%IBA)intermsofpercentagerooting,withlowerrates(1,250ppm)producingsimilarresultstohigherconcentrationswithmostspecies.The speed of rooting among the evergreen shrub specieswasquitesimilar,whethertreatedwithpowderorliquidhormonebutfasterwiththeconiferswhere‘quickdips’wereused.InfurthercomparativetrialsatHRIEffordovera four-yearperiodusingpowders(0.8%IBA)and‘quickdips’ofvaryingconcentrations,witharangeofautumnstruck semi-ripe cutting material, the ‘quick dips’ gave betterresultsthanpowderpreparations.Forexample,therewasamarkedincreaseinthespeedofrootingofElaeagnus pungens ‘Maculata’ and Mahonia japonica from ‘quick dips’ (1,500 ppm IBA gave good results), whileCamellia also rooted better from IBA ‘quick dips’ (2,000–4,000ppmIBA).Several Rhododendroncultivarswerealsoconsidered,including the popular ‘Cunninghams White’ and ‘Lady ClementineMitford’.Althoughresultswereagainvariable, on average, ‘quick dips’ gave slightly better rootingthanpowdertreatmentsalbeitatstrongerconcentrations(3,750–6,250ppmIBA).Erica carnea


‘SpringwoodWhite’alsorootedquickerwhentreatedwith‘quickdips’ascomparedtopowder(0.8%IBA).The trial also included Chamaecyparis lawsoniana ‘Columnaris Glauca’, ‘Pembury Blue’ and ‘Stardust’, alongwithX Cupressocyparis leylandii.RootingwasvariableamongtheChamaecyparislawsonianacultivarswith,onaverage,fewdifferencesevidentbetweenpowdersor‘quickdips’.However,X Cupressocyparis leylandiiprovedtheexception,withthe1,500ppmIBA‘quickdip’givingthebestresults.Note:Atthetimeofwriting,therearenoapprovedliquidrooting hormone products currently available for sale ontheUKmarketcontaininghighconcentrationsofIBAfortherootingofcuttings.Theonlysuchproductcontaining IBA for making liquids is the Rhizopon AA50mgwatersolubletabletandthemaximumconcentrationofIBAcurrentlypermissiblewiththesetabletsinwateris1,500ppm(30tabletsRhizoponAAperlitreofwater).

Hormone dips and drying off timesAcomplementarystudyundertakenatHRIEffordduring1982examinedtheeffectsoftimeofimmersioninhormoneliquiddipsontherootingofarangeofHNSspecies to establish if cuttings required the hormone treatmenttobedriedoffbeforeinsertionintotherootingmedium.Thetreatmentscompriseda‘rapiddip’(immediatewithdrawal)andastandardfive-second‘quick dip’ and compared the rooting of treated cuttings eitherinsertedwetimmediatelyafterdippinginhormoneordriedoffbeforeinsertion.ThespeciesusedwereEscallonia ‘Crimson Spire’, Hebe(speciesunspecified),Hypericum calycinum and Juniperus sabina tamariscifolia.AllcuttingswerestruckduringearlyFebruaryandrootedunderpolythenecovers.With each of the four species, there appeared to be no needtoallowcuttingstodrybeforeinsertionintotherootingmedium.Infact,withEscallonia and Hypericum, resultswereslightlybetterifmaterialwasinsertedwet,immediatelyafterdipping.Withthesetwosubjects,the‘rapid dip’ produced equal or better results than the five-second‘quickdip’.Thecommercialsignificanceofthisworkliesintheconsiderabletimesavingsthataccruewhencuttingsare ‘rapid-dipped’ and inserted immediately rather than driedofffollowingthestandardfive-seconddip;thisisanespeciallyimportantconsiderationwherelargevolumesofcuttingsarebeinghandled,andlinkswellwiththeADASsystemforhandlingcuttings.However,thespeciesusedinthistrialwererelativelyeasyrootingandthefindingsneedconfirmingthroughcommercialexperiencewithawiderrangerofHNSsubjectsthatareknowntobemorechallengingtoroot.

Propagation containersSelecting containers that enable good root development is crucial for the successful establishment of plants followingpropagationandtransplanting.Pointstoconsiderwhenchoosingpotsandtraysinclude:

• The percentage take and uniformity you are likely to achieve.Pre-formedcells(cellsthatholdorbindtherooting medium together) enable easy grading of slowerormoredifficulttorootsubjects.Rootedmaterial can also be readily spaced in situ

• Thetypeandsizeofcutting.Largercuttingswillrequirealarger,deepercellorpot,withmorespace

• The length of time the rooted cutting is likely to spend inthetrayorpot.Choiceisoftenacompromisebetweencostandthebestsizefortheplant

• Futurepotmoves.Rootedcuttingsarenormallytransplanted or potted on into larger containers, thesizeofwhichwillalsoinfluencethetypeand sizeofthatusedforpropagation.Avoidpotting smallrootedcellsintolargepots,particularlywithslowgrowingorsaltsensitivesubjects,eitherusealarger cell for propagation or a smaller (intermediate) potwhentransplanting

• Automation(forseedingortransplanting).Automationwillsavealotoftimebutonlyifthereissufficientvolumetojustifythecostandthechosenpotortrayneedstointegratewiththis

• Rootquality.Airpruningdiscouragesdamagingrootcirclingwhilepromotingstronglateralrootgrowthandsuccessfulestablishment.Traysthatpromotethis may be particularly useful for vigorous, fast rooting subjects prone to root circling and rooting throughintostandingbeds.Airpruningtraysrequiregoodairflowunderneathtoworkwell,forwhichopenbenching or raised beds are needed

winter.An example of root circling and constriction


Container selectionModuleorplugtraysofvaryingtypesandsizesarenowusedforHNSpropagationandlinkwellwithautomatedseeding units and transplanters to ease and speed up handling.Growthchecksarealsolesslikelycomparedwithstandardtraysasrootsystemsremainintactandsoundisturbedwhentransplanted.Preformedplugtrayswithready-to-userootingmedium,whilemorecostly,areconvenientandsavetime.However,very soft cuttings can easily snap during insertion, particularlywheretherootingmediumhasbeenovercompressed.Lackofuniformitycanalsobeaproblemintermsofmoisturecontentanddegreeofcompression.Root curling and constriction of young plants causes stuntingandpoorgrowthbutcanbeovercomebytheuseofbiodegradablecontainersorthoseformedwithgroovedinternalsurfacesthatchannelrootsdownratherthan round, so discouraging root circling (although good lateralrootgrowthmayalsobeconstrained).Biodegradablepotsalsosavetimewhenpottingonandreducenurserywastebutcanbeawkwardanddifficulttomanage,particularlyintermsofwatermanagementandnutrition.Variousmaterialsareavailableincludingpeat,coirandpaperwaste.While plastic pots and trays can be reused, they requirecleaninganddisinfectingtoreduceweedanddiseasecarry-overandstoring,whichiscostly.Therefore,newpotsandcarriertraysareoftenusedinstead or biodegradable types are used for some of theproduction.Thereisstillsomeuseofpolystyrenetrays,whicharelightweightandeasytohandlebuttheyaredifficulttocleanandreuseand,likeplastic,requiredisposal,whichiscostly.Loose-fillandpreformedplugtrayseachhaveadvantagesanddisadvantagesintheiruse;Table8providesaquicksummaryofeachtype.

Plugtrayswitharangeofcellsizesareavailableand choosing the most appropriate size is crucial to successfulpropagationandpost-rootingperformance.Larger, heavier cuttings usually require a larger cell size,bothintermsofdiameteranddepth.Ifthecellsare too small, rooted material can become constricted, quicklydryoutandrunshortoffeed.Largecuttingsandseedscanalsobedifficulttoinsertorsowaccurately.Conversely,toolargeacellcanwastevaluablespaceandincreasehandlingandtransportcosts.High levels of soluble salts and moisture around emerging roots can also develop and pose problems withlargecells,particularlywithslowrootingsubjects.Afurtherconsiderationisthenextactionfollowingrooting;forlinerpotting,smallcellsthatrootfasterandarequickertopotonareusuallypreferredwhilelargercells are easier to ‘hold’ and lend themselves better topottingonintolargerpots,typically1-litreupwards.

Cultural considerationsContainers,growingmediaandbedsusedforpropagationmustbewelldrainedtoavoidover-wetconditions,whichwillimpederooting.Drainedsandbeds are ideal (the sand should be of a grade similar to that used for capillary sand beds, comprising a range of particlesizes(30–40%greaterthan0.5mm,40–60%at0.5–0.2mmand5–15%lessthan0.2mm).Goodcontactbetweenthebaseofthetraysorpotsandthebedsisimportant.Ideally,sandbedsshouldbeuncoveredtomaximisecapillarycontactandwatermovementbetweenbedsandcontainers.However,rootingthroughandsubsequentgrowthcheckscanbea problem unless rooted material is removed promptly, especiallywithvigoroussubjects.Permeablegroundcover fabrics can be used over the beds to help reduce thisproblembutmayimpaircapillarycontact.

Table8.Theadvantagesanddisadvantagesofloose-fillandpreformedplugtrays

Loose-fill plug trays Preformed plug trays

Advantages Advantages

Cheaper to buyAvailable in a range of types and sizesGreaterchoicewithpropagationmedium,particularlywhenmixed in-houseControl over compression to minimise damage to cuttings duringinsertion,especiallywithsoftmaterialArguably, greater uniformity in terms of moisture content and firmness

Convenient,readytouseandsavestimeotherwisespentfillingtraysEasier and quicker to extract during transplantingAvailable in a range of types and sizes depending on requirementsAvailable pre-drilled for rapid insertion of cuttingsEasier grading of rooted cuttingsLittle or no root disturbance at transplanting

Disadvantages Disadvantages

Propagation media has to be mixed or bought in and handled separately,traysneedtobefilledRootedmaterialisslowertoextractandhandlewhentransplantingMore root disturbance likely

Moreexpensivetobuythanloose-filltraysMore limited choice of propagation mediaCanlackuniformity(variablefirmnessandmoisturecontent)


While rooted plant material can be held back until required by environmental control and manipulating nutritional regimes, material should not be left for long periodsbeforetransplanting,otherwiserootconstrictionwilloccur.Thisdelaysestablishmentandcanleadtolosses.Heavilymattedrootiseasilydamaged.Rootedmaterialthatisactivelygrowingcanalsoquicklyrunshortofnutritionordryout,eachofwhichcanseverelychecksubsequentgrowthandestablishmentandsorequireregularmonitoring;insuchsituations,automaticcapillaryirrigationisideal.

Propagation media and nutritionResearch into propagation mediaWhile easy rooting subjects usually propagate quite readilyinarangeofmedia,therootingofmoredifficultspeciesisinfluencedmoresignificantly,intermsofpercentage rooting, by the quality of rooting and the speedofrooting.MuchoftheearlyworkwithHNSpropagationmediawasundertakenatHRIEffordduringtheearly-mid1980s.Principally,itfocusedonthedevelopmentof granulated pine bark as a rooting medium in combinationwithpeattoimprovethespeedandqualityofrootinginsoftwoodandsemi-ripecuttingsandtheuse of controlled release fertilisers for post-rooting nutritiontomaintainquality.InitialworkfocusedonbarkasitwaswidelyavailableandcommercialexperiencewithithadbeendevelopedelsewhereinEuropeandintheUnitedStates.EarlyworkintheStates,forexample,foundthatfinerootspenetratedintobarkparticlesorgranulesaswellasbetweenthem,soenablingthedevelopmentofstronger,denserrootsystems.Mixesof50:50peatandbarkand100%barkwerecomparedwith75:25peatandgrit,withandwithoutcontrolledreleasefertiliser.Thenitrogenimmobilisationpropertiesofbarkprovidedanimportantbufferagainstthe‘flash’releaseofnutrients,whichimpedesrooting,particularlyundercoverandwherebaseheatisused.While 100% pine bark promoted rapid root development,itwasmoredifficulttomanageduringtheweaningphaseduetodryingout.The50:50peatand bark mix improved rooting and cutting quality acrossarangeofHNSsubjectscomparedwithpeat:grit,providedthatacontrolledreleasefertiliserwasincorporated.Withoutthis,resultswereinfactpoorer.Thismixwasalsoeasiertomanagethan100%bark.Significantly,thisworkunderlinedthevalueofthenutrientbufferingeffectofbark-basedmixes,whichprovedsaferthanpeat:gritmixeswherecontrolledreleasefertiliserwasused,protectingyoungrootsfromtheeffectsofhighsaltsand,togetherwiththestructuralbenefitsofbark,improvingthequalityofrootedmaterialandthespeedofestablishment.AtHRIEfford,whilethiseffectwasparticularlystrikingwithCamellia,allwinterrootedevergreenandconiferspeciesscreenedshowedgreateruniformityofgrowth.

Inthesameprogrammeofwork,trialswithsprucebarkdidnotgiveasgoodaresultaspinebark.Mostrecently,materialssuchacoirandwood-fibrehave been successfully used for rooting cuttings, particularlycoir,whichhasperformedwellacrossarangeofHNSsubjectswhencombinedwithbarkforcommercialHNSpropagation.Regardless of the materials used, propagation media should be:

• Readilyavailableandaffordable• Clean,lightweightandeasytohandle• Physically uniform and stable

• Robust and able to support cuttings, particularly ‘heavy’ semi-ripe evergreen species

• ConsistentintermsofpH(5.5–5.6istheoptimumforgeneralHNS)andnutrientcompositiontomaintainquality post-rooting

• Flowableintermsofpotortrayfilling

• Sterileintermsofpest,diseaseandweedcontamination

• Non-phytotoxicandreadilypenetrableby young roots

• Welldrainedandmoistureretentivewithanadequateair-filledporosity(AFP)

Therootingmediummustbewelldrainedandprovideadequate oxygen around the base of unrooted cuttings, whichutilisecarbohydratetoformnewtissueandsorespirerapidly.Poorgrowingmediumstructureanddrainage is a common cause of cuttings failing to root, especiallyinpoorlycontrolledmistorfogsystems.Damping-offdiseasesmayalsooccurandexacerbatetheproblem.At the other extreme, too much aeration can lead to excess callus formation at the expense of root initiation (commonly seen in Camellia, Leyland Cypress and Taxus species, for example) and cuttings becoming unstable.Theremustbeabalancebetweengooddrainageandmoistureretention.

Physical raw materials for propagation mediaPeatPeatremainsthemostpopularandwidelyused bulkingredientinnurserystockproduction.However,environmental and legislative pressures to reduce its useandseekalternativescontinue.Forpropagationpurposes, good quality medium-grade sphagnum peat is the most suitable as it retains moisture and isstable,uniformandchemicallyinert(whichenablestheeasyadjustmentofpHandnutrientlevels).Intermsofstructure,peatsusedforHNSpropagationshouldhaveanair-filledporosity(AFP)ofIndex2(10–15%)althoughfinerpeatsareoftenusedfor seed propagation and cuttings rooted in small modules,usuallyinblendswithperliteorvermicullite.


Bark and other wood-based materialsGranulated pine bark has an open structure that providespropagationmixeswithgooddrainageandaeration, so complementing the moisture retaining propertiesofpeatorcoirfibre.Itisalsolightweight,sterile,chemicallyinertandprovidesausefulbufferagainstexcesswaterorsolublesalts.Thisenablestheinclusionofcontrolledreleasefertiliserproductswithinmixes used for rooting cuttings, a major advance in termsofpost-rootingnutrition.Bark is especially good at promoting rapid root growthandthedevelopmentofafibrousrootsystem,whichhastenstheestablishmentofcuttingswhentransplanted.However,itimmobilisesnitrogenleadingto depletion and loss of quality, necessitating the use of base fertiliser or supplementary nitrogen in potting mixes(unlessliquidfeedingisavailable).Thisisusuallyunnecessaryinpropagationmixeswheretheinclusionof controlled release fertiliser (or liquid feeding) provides sufficientpost-rootingnutrition.Granulated pine bark is preferred to spruce and larch barkasitusuallyhasfewervolatileoils.ItalsohaslowercalciumlevelsandalowerpHvalueandsoismoresuitableforHNSsubjects.Barkisnowwidelyusedfortherootingofcuttings,usuallyinmixeswithpeatorcoirtoaidnutrientandwaterretentionduringpost-rootingnutrition.Theaddition of peat or coir enables easier insertion and supportofcuttingswithintraysorpots.Barkcanhaveausefulsuppressanteffectonsoilandwater-bornediseasepathogens,notablyPythium and Phytophthorabothofwhichareinvariablylinkedwiththe‘damping-off’ofseedlingsandcuttings.Asitbecomesmorewidelyavailable,wood-fibreisnowalsobeingusedinpropagationmedia.Coir fibreThephysicalcharacteristicsandwater-holdingcapacityofcoirfibrearequitesimilartopeat.Itis,therefore, easytooverwaterandoftenappearsdryonthe surfacewhilebeingadequatelywetunderneath.Butit can also dry out quickly and so requires particularly carefulmanagement.Nitrogenimmobilisationcanoccur,leadingtoleafyellowingsymptoms.ThesesymptomsmayalsobeduetotheinitiallyhighpHofcoir,apointtoconsiderwhenaddinglime.WhilecoirisnowusedmorewidelyforcontainerHNSproduction,usuallyinblendswithpeatand bark, it is also an excellent propagation substrate fortherootingofcuttings,particularlywhencombinedwithgranulatedpinebark(50:50byvolume).Sand and gritSand and grit are relatively cheap and available but vary intheirphysicalandmineralcomposition.Theyarealsoheavyandaddconsiderableweighttoapropagationmedium,whichisanimportanthandlingandtransportconsideration.Theyalsoretainlittlewaterandsorequireblendingwithothersubstrates,usuallypeat.Assuch,

their commercial appeal has diminished in favour of morelightweightmaterials,notablybarkandcoirfibrebutalsoperliteandvermiculite.For some subjects, sharp sand, a non-calcareous sand derived from sandstone or granite, should be used, withagoodspreadofparticlesizes(0.01mmto3mm).Addition does provide the necessary sharpness and physicalsupportduringrooting;Taxus, for example, andmanyotherconifersrespondwelltotheuseofasharp sand as do Magnolia species (although, these alsorootwellin50:50blendsofpeatwithbark).OtherHNSsubjects,though,producelong,unbranchedratherbrittlerootsystemsratherthanthemorefibroustypesdevelopedwithbark.PerliteAn inert material of volcanic origin that is heat treated to form stable aggregates, perlite is clean, easy to handleandlightweighttouse.Itiswidelyusedforseedandsoftwoodorsemi-ripecuttingsduetoitsgooddrainagecharacteristicsandisoftenusedwithpeatorbarkwherefreedrainageisrequired,usuallyatratesof20–30%byvolume.Unlikevermiculite,ithaslittleornobufferingcapacitybutitissometimespartneredwithit,usuallywithmediumgradesphagnumpeat.ForHNScuttingspropagation,thehorticultural grades (medium or coarse) of perlite should be used andnotthosecontainingahighpercentageoffineparticlesordust.VermiculiteVermiculiteisanaturallyoccurringlightweightmineralalso created by heat treatment to produce a material of highporosityandgoodairtowaterratio,withausualpHof6.0–6.5.Itisoftenusedasasurfacedressingin seed propagation over trays or modules to retain moisture, protect seeds and exclude light, and in propagationmediaasamineralbufferagainstexcesssalts,usuallyat20–30%byvolume.HNScuttingsgenerallyrootbetterinvermiculiteifthelargerparticlesizesareused.Magnolia cuttings respond particularlywelltovermiculitewhenitismixedwithpeat,formoistureretentionandsupportofthecuttings.RockwoolAninert,fibrous,lightweightandsterilesubstratederivedfromvolcanicrock,capableofrootingHNScuttings,duelargelytoitshighaircapacity.Usedquite extensively during the 1980s, commercial experiencewithitwasmixed.Whiletheslow-rootingBerberis types, Ceanothus, Cotoneaster, Elaeagnus, Escallonia, Garrya, Lavatera, Spiraea, Viburnum davidii and Viburnum tinusrootedwell,othersprovedlessresponsive, notably Cytisus, Euphorbia, Pernettya and wintercuttingsofIlex and Laurus nobilis and Photinia, whichdidbetterinapeatandbarkmedium.ItisnotwidelyusedforHNSpropagation,duelargelyto its high cost, variable results and concerns about the environmentalimpactofitsuseanddisposal.


NutritionHistorically, nutrients to maintain quality and promote rootdevelopmentinapropagationmediumwereprovidedbysuperphosphates,groundchalk,lowratebase fertiliser dressings and, prior to the development ofpeat-basedmedia,theinclusionofloam.However,modernproductionthatbuildsontheHRIEffordworkusesmoreefficientcontrolledreleasefertilisersthatprovidenutritioninlinewithtemperatureandgrowthrequirements.GroundchalkorMagnesianlimestone(‘Dolodust’)arenowusedforpHadjustment.Theprincipalbenefitfromfertiliserincorporationintherooting medium is the improved establishment and early qualityandspeedofgrowthofcuttingsoncepottedon.AtHRIEfford,whilethiseffectwasparticularlystrikingwithCamellia,allspeciesscreenedshowedgreateruniformityofgrowthand,whiletheeffectwaslessobvioussixmonthsafterpotting,itwasstillevidentamong Camellia and X Cupressocyparis leylandii.Inearlystudieswithwinterrootedevergreensandconifers, including Camellia, X Cupressocyparis leylandii, Griselinia and Pittosporum, leaf-tissue analyses prior to potting on of rooted cuttings also showedthattheinclusionofcontrolledreleasefertiliserreduced nitrogen depletion from the cuttings during propagation,whichhelpedtoimprovefoliagecolour,particularlyamongconifers.The type and rate of controlled release fertiliser used in propagation media is critical, especially under the highertemperaturesofpolythenecovers(wherethereislessleachingofexcesssaltscomparedtomist).Inearlytrials,ratesof0.5and0.75kg/m3 of medium-term productsgavegoodresults,particularlywith50:50peatandbarkmixes.Longer-termproducts(12–14month)weresaferandenabledhigherratesofuse(0.75kg/m3), withtheinclusionofbark.ThiscombinationbecametheHRIEffordstandardpropagatingmediumforallwinterpropagationunderpolythene.

winter.Effectofcontrolledreleasefertiliserintherootingmedia,left liquidfeedingfollowingweaningand,right,fertiliserincorporationin the tray

Subsequentworkfoundscopeforincreasingthefertiliserratebeyond0.75kg/m3 of the 12–14 month product,providedbarkwasused,whichledtotheuseofhigherrates(typically,1.5–2.0kg/m3)bygrowers,

forexample,withvigorousspeciesrootedunderthesaferenvironmentofmist(ratherthanpolythenetents).HRIEffordworkalsoindicatedthatbarkmixesproducedmorenewrootgrowthcomparedwithcuttingsrootedinfibrouspeatandgritmixes,particularlywherefertiliserhadbeenincluded.Asinprevioustrials,thesebenefitscontinuedafterpotting,resultinginfasterestablishment,earliergrowthandgreateruniformitywithinthebatch;effectsthatwerestillevidentsixmonthsafterpotting.

winter.Thebenefitsofincludingcontrolledreleasefertiliserwithbarkinthe rooting medium, from left to right, no feed during propagation, liquidfeedingafterweaningandfertiliserincorporation

TheHRIEffordstudiesalsofoundthatthetypeandrateoffertilisertousevariedwiththetimeofpropagationandinturnthesystemused.Duringthespringandsummermonths,forexample,whenmistorfogenvironmentsarewidelydeployed,thereisscopetousehigherfertiliserrates(1kg/m3 of 8–9 or 12–14 month products gave excellent results across a range of subjects)butforautumnandwinterpropagationunderpolythenecovers,whereleachingisminimal,lowerrates(0.75–1.0kg/m3)ofa12–14monthproductweresaferyetstillprovidedsufficientnutrientreservestomaintaincuttingqualityuntilspringpotting.


SeedSeed sourcesAlthough there are many good seed houses dealing in plantsfromtemperateclimates,whichsupplyseedsinexcellent condition, harvesting seed from local sources to augment commercial supplies and broaden the range ofspecieshasadvantages.Forexample,itenablestheidentityandqualityofthematerialtobespecificallydeterminedandcontroloverthetimingofcollection. In turn, this creates the potential for greater certainty andsooffersamorereliableoutcome.Theprovenanceof locally collected seed also provides a strong indication of the likely performance of that particular speciesinthelocalenvironment.If obtaining seed from local sources, the most important considerationistodetermineandconfirmtheidentityofthesubjecttobepropagatedanditstruenesstotype.It is also important to assess the available plants that are producing seeds in order to select the most suitable parent.Moreoftenthannot,therewillonlybeone seed-bearing parent plant available but there may beseveralspecimensthatexhibitsufficientlysimilarcharacteristicstodemonstratereasonableuniformity. Atthisstage,itisalsousefultodeterminewhetherthesepotential parents are seedlings or are of vegetative (clonal)origin,asthiswillgovernthelimitsoftheavailablegenepoolanditspotentialforvariation.Insituationswhereotherrelevant,relatedspecies aregrowinginthesamearea,thepotentialfor cross-pollinationandtheproductionofhybridoffspringshould be considered and thus seed collection avoided fromsuchpotentialparents.Seedling and plant vigour are largely governed by genetics, and seed collected from a group of plants of the same species that cross-pollinate is more likely tohavegoodvigour.Assuch,itislikelytoperformmuch better at the seedling stage compared to progeny resulting from seed collected from isolated, self-pollinatedindividuals.Monitoringeachseed source is, therefore, important to ascertain its suitabilityforfutureseedcollection.Trueness to type of the resultant seedlings also requirescheckingbecause,whileaparentplantitselfmay appear to be correct, it may in fact be derived from a cross and characteristics that indicate this only tend toappearinthenextgeneration.Influence of parent plants on seed productionWhen collecting seeds from plants that have only recentlymatured,beawarethatmostfoodreserves arestillbeingchannelledintovegetativegrowth.Normally,therefore,thelevelofseedproduction willberelativelysparseandthequalityofanyseedsproduced, especially in terms of the amount of stored foodreserve,maybelow.As the plant progresses further into the mature phase, theamountofannualvegetativegrowthdeclines and seed production in both quantity and quality potentiallyimproves.Atthisstage,vegetativeextension

growthhasmoderatedconsiderablyandtheplanthas reached the greater part of its ultimate height and spread.Thisincreaseandstabilisationofthegrowthpattern is accompanied by maximum leaf area and by anincreasedpropensitytoproduceflowers.Asaresult,high-qualityseedsmayfollow,untilthesenilephaseapproaches,whentherewillprobablybeaflurryofheavycropspriortodeath.The established mature plant is, therefore, diverting its resources into the development of both the embryo and the food reserve of the seed, and a good crop canbeanticipated.However,especiallyintheUK,thistheoreticallevelofseedproductioncanbeaffectedby environmental conditions in any particular year, for example,frostoccurrenceatfloweringandlowsummertemperatures,aswellastheincidenceofleafpests anddiseases.Season of collectionNormally,itisanticipatedthatseedswillbecollectedjustpriortodispersalwhenallofthebiologicalprocessesinvolvedwiththedevelopmentoftheseedhavebeencompleted.Atthisstage,theseedismatureandwillbesuitableforgerminationorstorage.However,thereareasignificantnumberofspeciesofwoodyplants(suchasAcer campestre, Acer palmatum, Carpinus betulus, Daphne mezereum,etc.)forwhichthis is not necessarily the best strategy as, by this stage, theseedwillhavedevelopedintransigentdormancyconditions.Itis,therefore,prudenttocollectsuch seedsatanearlierstage.Periodicity of seed productionThere are many tree species (including Fagus sylvatica, Quercus robur and Sorbus aria) that exhibit a periodicity in the production of seed crops and, as such, the productionofprolificharvestswillonlyoccuratinfrequentintervals,referredtoasmastyears.Insuchcases,itisimportanttogathersufficientcropintheproductiveyearstoaccountforthedeficiencyintheotheryearsbystorage.This more or less genetically controlled condition shouldnotbeconfusedwithafailuretocropduetoa particular prevailing environmental condition, such asfrostincidence,whichmayaffecttheinitiationordevelopmentoftheseedatfloweringorfertilisation.

Seed viability, vigour and longevityWhendeterminingthesowingratesforasampleofseed, in order to achieve a predetermined density ofseedlingproduction,itisessentialtoknowwhatproportion of the sample is viable and so, potentially, capableofdevelopingintoaseedling.ViabilityA viable seed is one that has the potential to germinate and establish as a seedling, given the provision of suitable conditions and, thus, be capable of producing bothasufficientrootandshootsystemtoensurecontinuingautonomy.

Propagation techniques

36 Propagation techniques

There can be several reasons for the lack of viability in seeds, notably:

• The absence of an embryo

• The presence of a malformed embryo

• Thelackofasufficientfoodreserve• An inability to mobilise or use the food reserves

• Physical damage engendered by the collection, extraction and cleaning treatments

• An attack by biological organisms causing degradation

• Ageingtoanirreversiblestateofdeterioration,whicheffectivelydoesnotallowtheprocessofgerminationto proceed

The potential viability of a seed lot is usually expressed as a percentage of the number of seeds present and reflectstheproportionofthesamplethatiscapableofsatisfactorygermination.Thisfigure,however,onlyrepresentsthepotentialatthetimethatitismeasured;seed viability naturally diminishes over time and is influencedbymanyenvironmentalfactors,makingaccurateassessmentoftherateofdeclineverydifficult.Thereare,however,severaltechniquesfortheassessment of viability under nursery conditions:

• Cutting test

• Germination test

• Excised embryo test

• Staining techniquesThe cutting test is the simplest operation to carry out, as it relies on exposing the internal tissues of the seed toobservation.Fromthis,byavisualassessment,thestatus and condition of the embryo and food reserves canbedetermined.The germination test provides a relatively more accurate assessment of the potential for germination that might beachievedunderoptimalconditions.Seedscanbesubjected to reasonably constant and reproducible environmental conditions that are suitable for initiating andsustainingtheprocessofgermination.Theresultsare measured by the seeds’ responses and these can thenbeevaluated.The excised embryo test is more complex and requires the availability of laboratory resources and the development of expertise in being able to dissect out theembryowithoutdamage.The technique involves the removal of the embryo from its surrounding tissues and seed coats and its transference to a moist situation in a petri-dish or similar receptaclewhereitcanbesuitablyincubatedandanyresponsesassessed.The use of staining techniques in determining the presenceandpatternoflivingtissuewithintheseedcanbeachievedusingarangeofstainingagents.Thereareanumberofsuchchemicalsthatwillachieveusefulresultspermittingavisualinterpretationofseedviability.

VigourThe measure of viability provides the overall picture of thestatusofaseedlotbutexperiencewillindicatethepotentialthislevelwillhaveontherateandstrengthofseedlingemergenceduringthegerminationprocess.Thisaspectisdescribedasthevigouroftheseedlot.When a seed is fresh and ready for dispersal there is normally no deterioration in the seed structure or the correspondingphysiologicalprocesses;themaximumnumber of embryos are viable and the necessary metabolicprocessesareatmaximumefficiency.Whenthe germination process is delayed, this causes damage and the deterioration of seed structures and processes willensue.LongevityThe term longevity, in the context of seed viability, is used to describe the length of life of a seed sample duringwhichsomeusefulcapacityforgerminationisretained.Itis,however,rarelydefinedinameasured wayandisoftenusedinarelativeorcomparativefashiontodeterminetheeffectofstorageconditions onmaintainingviability.Inpractice,thisperiodcan varyfromafewdaysasinthecaseof Acer rubrum, Acer saccharinum,manywillowsandpoplarstomanyyearsaswiththehardseededLeguminosae.

Collection and extraction of seedsSeed collection and initial handlingSeedcollectionlendsitselfwelltobusinesseswithanextensivecatalogueofsubjectsgrowninrelativelymodest quantities requiring small samples of seed eachyear.However,itistime-consumingandquitespecialistworkandtheeconomicsofthisapproachmustbecarefullyassessedfirstandcomparedwithcommercialsourcing.When collecting seed, the main objective is to harvest high-qualityseedsinsuchawaythatthereisnodetriment to the integrity and condition of the seed and its contents so that the highest level of viability andconditionismaintained.Donotwasteresourcescollectingsubstandardseed.The collection of seeds or fruits requires a number of preliminaries to be considered:

• Obtain the necessary permissions if required

• Determinethesourceandconfirmidentification

• Assess likely seed quality

• Assess seed quantity (monitor through season)

• Assemble the required collection equipmentTheactualcollectionprocedurewillalsorequiresomeattention:

• Collectwhenconditionsaresuitable,avoidveryhot,coldorveryrainyperiodsinwhichseedscanquicklydeteriorate.Seedcollectinginsuchconditionscanalsobearduouswork

• Adopt suitable methods to avoid seed deterioration

Propagation techniques 37

• Only collect manageable amounts of seed and keep it outofdirectsunlight.Itwouldalsobeprudenttoprovide a cool box for temporary storage and transport inordertoremovethe‘fieldheat’fromtheseeds

• Collect a clean sample, remove leaves and other detritus as you go

• Check to ensure there are no obvious pests, diseases or surface moulds present

• Do not collect fruits until they have reached such a stageofmaturitythattheywillreleasetheseedseasily

• Spread out collected seed evenly and thinly on a clean surface to prevent heating up

• Provide good air movement and turn seed periodically until the batch is cleaned, extracted anddealtwith

• Weargloves,dustmasks,etc.,whennecessary, to avoid allergic reactions

• As large amounts of big seeds or fruits are likely to heat up as a result of their normal metabolic activity, the material should be packeted into smaller units

• Keepaccuraterecordsofallseedcollectedforreference and future comparison

Seedcollectionandripeningmethodsvarywithspeciesandinturnthemethodofseeddispersal.Forexample,acorns (Quercus species) and chestnuts (Aesculus species)canbeharvestedfromthegroundwhileothers,such as elm seed (Ulmus species)requiresweepingup.Alternatively,sackingorpolythenesheetingcanbelaid on the ground around the plant that is then shaken toremovetheseed.Withsomespecies(forexample,Fagus sylvatica), nature must take its course and the seedcollectedoveraperiodoftime;thisrequiresdiligentmonitoringtojudgewhenbesttoplace nettingorsackingdownforcollection.Berries usually require hand picking from the plants, although major specialist seed producers collecting largebatchesofseed,generallymechanisethework.Whenhandpickingseed,verydenseplantgrowthinvariablymakestheuseofacollectionsackdifficultand, in such situations, it is often quicker to place sackingorsheetingunderneaththetreeandallow theseedbeingpickedtofallnaturallyontoit.Ifcollectingseedbyhand,careshouldalwaysbetakentoavoidremovingspursorsmallbranchesthatwillbearsubsequentcrops.Alackofdiligenceinthisrespectcanquickly reduce future seed crops and increase the cost ofseedcleaningwork.Use hessian sacks, rather than polythene bags for collectionofseed.Labelpromptly,withthecorrectname,dateofcollectionandsourceofmaterial. Usewaterprooflabelsandmarkerpens.Seed extractionThe principal objective in the extraction of a sample of seed from its surrounding fruit is to avoid damage to the structure and integrity of the seed or to reduce the level ofseedviability.

The extraction of seeds from the fruit is achieved byeitherofthefollowingprocesses:

• Separation of the seeds from multi-seeded fruits into single entities

• Separation of the seed from the remainder of the fruit, in order to obtain a clean sample

The process should be achieved:

• With the minimum of damage to the physical integrity of the seed

• With the retention of acceptable levels of quality

• Without altering the internal physiology of the seed andespeciallywithoutenhancinganydormancyconditions or inducing secondary dormancy

• Without enhancing any seed coat condition associatedwithmoisturepermeability

• Withoutcriticallyaffectingthemoisturecontentof the seed

Methods of seed extractionThe actual methods of extraction are as disparate astheindividualtypesoffruitthemselves.Itis possible to describe various generalised methods of seed extraction but, importantly, each sample should bedealtwithonanindividualbasis.Theprocess should be monitored continuously in order to modify the action of equipment or the treatment process itself tosuiteachsample.Thestatusoftheseedshouldberegularly assessed in order to maintain quality control andsoproduceasamplewiththehighestcapacity toregenerate.Extracting seeds from dry fruits and conesThis relates to those plants that liberate their seeds from the fruits simply as a result of drying and is quite a commonprocess.Aswateriswithdrawnbytheparentplant or is lost by the action of external factors, the fruits maturetothepointatwhichtheyopen.Fruitscanopengradually, disintegrate or even explode depending on theirmodeofdispersal.Fruits of this type should be collected as they become fullymatureandareapproachingthestageatwhichtheywillopentodispersetheseeds.Thetimeofcollection is often critical as drying of the fruits, using an artificialsource,willnotnecessarilyproducethecorrectdryingprocessresultinginthepointsofweaknessnotbeing triggered so that fruits remain stubbornly closed, forexamplewithCeanothus, Euonymus and Magnolia.The cones of conifers, in general (not those producing afleshyfruitorserotinouscones),normallyopenandliberate their seeds as a result of a natural drying process.Asharvestedconesarenecessarilycollectedbefore they open and liberate their seeds, the cones can bedriedartificiallyingentle,drywarmthwheretheywillrespondwithoutdifficultyandopensuccessfully.Onalarge scale, this activity can be undertaken in a suitable kilninwhichtheconescanbetumbledriedatnomorethan60°C.Thiswillachievesatisfactoryresultsandacleansampleofseedswillbeproduced.


If the cones are of the type that break up to liberate the seeds,itwillbenecessarytofantheresultingmasstoseparatetheseedsfromthescales.Serotinous (closed) cones can usually be opened by flamingthemoverafire.However,iftheyareparticularlytightly closed and do not respond, they should be soaked,thenfrozen,thawedanddried.Theseeds willshakeoutoncethescalesopen.Extracting seed from fleshy fruitsFleshyfruitsofwhatevertype(drupes,pomes,berries,etc.)havegenerallyevolvedasamodeofdispersalfortheseedandrepresentthevariouswaysofattractingananimalbyprovidingafoodresource.Theattractionis often enhanced by the development of colour that identifiesthefoodresourceandthestageoftheirdevelopmentintermsofpalatability.Fruitsofthistypewill,moreoftenthannot,containseedswitha‘hard’seedcoat,whichprovidestheprotection for it to avoid damage as it passes through theanimal’sdigestivetract.Usually,theseedcoatwillhavebeendegradedclosetoalevelallowingwaterpermeabilitywhenitiseventuallyexpelled.Artificialextraction does not achieve this degradation so it is important that the process does not enhance the conditionthatusuallyoccurswhentheseedisdriedmorethanisnecessarytosurfacedry.Soakthefruitsinwarmwaterforaperiodto encouragefermentationoftheflesh;eventually,withsomeagitation,itwillseparateandfloatsothattheseedsfalltothebottom.Theliquidcanthenbedecantedoffandtheseedswashedcleanandthensurfacedried.Donotallowtheprocesstogobeyondthestageatwhichseparationcanbeachievedtoavoidanydetrimenttotheseeds.Washtheseedswithasmallamount of detergent in order to remove any residual fat thatmayaffectwateruptakebytheseedoranyfleshorskinthatmaycontaingerminationinhibitors.

Seed dormancyWhen a viable and quiescent seed is subjected to conditions suitable for germination and it does not respond,theseedissaidtobedormant.Thisimpliesthat there is present, in the make-up of the seed or its coverings,amechanismforpreventinggermination.Althoughdormancypresentsdifficultiesforthepropagator, the condition is an evolved strategy that particular species have developed to enhance survival, oritmayalsoreflecttheneedtospreadgerminationovertime.Ithasevolvedtoensurethatgerminationandestablishmentoccurswhenthemostsuitableenvironmental conditions for the survival of the seedling are available and conversely that germination ispreventedwhenconditionsareadverse.Itmayalsodelay germination spasmodically over a number of years inordertoachievesuccesswhensuitableyearsoccur.Some seed coat conditions have also evolved to protect theseedfromdigestionwhilepassingthroughthegut ofananimal.

Propagators need to recognise and overcome these limitations to enable seed germination to proceed in ordertoachievethebestproductivity.Inbroadterms,seeddormancyinwoodyplantsfromtemperate climates can be attributed to:

• Externalconditions,inwhichtheseedcoatmaypreventtheuptakeofwater,restrictgaseousexchange or limit embryo expansion

• An immature or rudimentary embryo

• Biochemical conditions that inhibit endogenous physiological reactions that form part of the germination process

Hard seed coatsMany plants (for example, Crataegus, Prunus and leguminous species such as Acacia, Cytisus and Ulex) produce seeds that develop a hard seed coat, the commonestformofwhichisahardstone-likeor shell-likestructure.Theeffectivemethodofreducingthistoawaterpermeable condition varies from caustic digestion, through heat treatment, physical and biological degradation,towarmwatersoakingdependingonthedegreeofseedcoatdevelopment.Tough seed coatsThe types of seed coat that constitute this category are quite varied in their constitution but all are to some degreeleathery.Theyare,whenfullydeveloped,pliable,toughandimpermeabletowaterandhaveamoreorless constant and uniform consistency or sometimes haveareticulatestructure.Allareintractable,insofarastheartificialremovalofseedcoatmaterialisdifficultandoftenhazardous.Although it is possible to degrade them by digestion withacidorothercausticmaterials,thisisusuallydifficulttodo.Thoughslower,theuseofanaturalmaterial that degrades the seed coat biologically is safer andcanbedoneeffectively,ifnotwithgreataccuracy.Waterproof seed coatsAlthough fairly uncommon, there are several plants (including Aesculus, Cedrus and Wisteria)forwhich the seed is maintained in a quiescent state by a surfacewaterproofing,whichpreventstheingress ofwater.Materialssuchaswaxes,fatsandoilsare themostcommonlyfoundagents.Oftenthecondition is only short lived but, should it need to be removed, hotwatersoakingisusuallysufficient.Immature and rudimentary embryosInmanyspeciesofwoodyplants(forexample,Fraxinus excelsior, Ilex, Podocarpus and Taxus), the process of germination is prevented simply because the embryo hasnotdevelopedtoasufficientlymaturestageforgerminationtooccurwhenconditionsaresuitable.Thecondition can be mitigated by storing the imbibed seed at awarmtemperature(around20°C)forasufficientperiod(usually4–12weeksdependingonthespeciesandseason)toallowthematurationprocesstobecompleted.


Endogenous dormancyThistypeofdormancycontroloccurswithintheseeditself and depends on the presence of particular chemicals that prevent or interrupt the normal patterns ofmetabolicactivityandgermination.Currently,itwouldappearthatthepreventionofgermination of the imbibed seed is caused by the presence of inhibitors that the seed has metabolised duringthematurationprocess.Thechiefrecognisedagentisabscisicacid.Furtheractivitythendependsonthereductionoftheleveloftheinhibitorwithacorrespondingincreaseintheproductionofthegrowthpromoter(usuallycitedasagibberellicacid).Thistypeof dormancy can be mitigated by the exposure of the imbibedseedtoaperiodofcoldtemperature.Epicotyl dormancyTheconditionknownasepicotyl(double)dormancy,although not uncommon in herbaceous plants, especially the Liliaceae,isnotcommonamongwoodyplantsingeneral.Itistypifiedbytheemergenceoftheradical,fromtheimbibedseed,duringthefirstwarmperiodafterdispersal;however,theplumulerequiresaperiodofchillingbeforeitwillgerminatewhenconditionsareagainsuitable.Thisusuallymeansthattheseedbedisoccupiedfortwogrowingseasonsbeforetheseedlingisproduced.ExamplesamongwoodyplantsthathaveadoptedthisstrategyincludeChionanthus, DavidiaandsomeNorthAmerican species of Viburnum.Multiple types of dormancyItisnotuncommontofindamongwoodyplantsfromtemperate climates, the development of more than one typeofdormancy.Innature,thisusuallyensuresthespreadofgerminationovermorethanoneyear.Thismorecomplexpicturecreatesfurtherdifficultiesforthepropagatorbutitcanbedealtwithbyeliminatingtheconditionsinsequenceinordertoachievegermination.In some species this entails, at the extreme, all three modes of dormancy and involves in order of elimination a seed coat condition, an immature embryo and a chillingrequirement.Theclassicexponentofthis state is Fraxinus excelsior.Avoiding dormancyDormancy caused by intransigent seed coat conditions are conventionally overcome by the degradation of the seedcoatbycausticagentsforswiftresultsornaturalmethodsthatarerelativelylongtermanddifficulttodevelopaccurately.Ideally,themostsuccessfuloutcomewouldbetobeabletocollecttheseedbefore any of these conditions have developed in the maturationprocessoftheseed.Although it is currently not feasible to avoid endogenous dormancy conditions, it is possible to avoid those dormancy conditions that are controlled by the condition of the seed coat, by harvesting the seed as soon as it is mature and before the seed coat condition hasdeveloped.

Even30yearsago,itwasbarelyrecognisedandaccepted that the collection of the seed, at the point of maturation and before the development of the impermeableseedcoat,wasfeasibleandcouldbeundertakenwithoutanypotentialdamage.However,theconceptisnotnewandaslongagoas1945,VanderGraafintheNetherlandspublishedonthis topic in relation to Daphne mezereum.PlantsinaswidelydivergentgeneraandspeciesasAcer campestre, Acer truncatum, Hamamelis mollis, Carpinus betulus and Viburnum lantana haveallbeenshowntorespondtoanadaptationofthistechnique.

Seed storagePrinciples of seed storageIn essence, the principal aim of any storage technique is to extend the longevity of a seed lot by maintaining the highestfeasiblelevelofviabilityforaslongaspossible.This extension is achieved by the provision of environmentalconditionsthathavetheeffectofreducingtherateofdeteriorationoftheseeds.Themostusualarethosethatslowthemetabolicprocesses,especiallytherate of respiration of the seed and that can be applied underpracticalcircumstances.Inpractice,threefactorsare relevant: temperature, seed moisture content and the gaseousconstitutionoftheatmosphere.Therateatwhichbiologicalprocessesoccurisrelatedto temperature and, as such, this is one of the most commonlymanipulatedparametersinseedstorage.Asageneralrule,thecolderthetemperature,theslowertherateofreactionwillbe.Thus,atalowtemperature, therateofrespirationislower,foodreservesaremobilisedandconsumedmoreslowlyandtheconsequentancillaryprocessesareslower.Anyreductionoftemperaturewillenhancelongevitybutthemosteffectiveresponseisachievedatthelowesttemperaturethattheseedwilltoleratewithoutdamage.Inpractice,formostwoodyplantsoftemperateprovenance,astoragetemperatureof2–3°Cisadequate to achieve the level of longevity required forcommercialpurposes.Atthislevel,anormalhousehold refrigerator can be manipulated to maintainsuchatemperature.Historically, the most favoured method of increasing the longevity of a seed lot is to reduce its moisture contentbutmanyspeciesofwoodyplantsstoretheirfoodreservesintheformofproteinsorfats(aswellas carbohydrates) and these materials do not lend themselveseasilytorehydration.Although rarely practiced, it is also possible to slowmetabolicprocessesinseedsbyreducingtheavailabilityofoxygen.However,thispossibilityshouldbetreatedwithcareasawholesaleremovalofoxygencould induce an anaerobic response if the other parametersarenotalsocontrolled.

Practical aspects of seed storage


Forsuccessfulstorage,seedmustbemature,withadeveloped and quiescent embryo and have a stable foodreserve.Generally,seedswithahighoil(fat)content, such as Abies and Cedrus, don’tstorewell.

winter.Good seed storage maintains viability and enhances longevity

Seeds should be processed and stored as quickly aspossiblefollowingcollection,whilefreshandingoodcondition;theyarethenmorelikelytomaintainviabilityinstoreanddeterioratemuchless.Whilesome nurseries still use cold storage or other chilling techniquestobreakseeddormancy,manynowbuyintheir seed requirements, pretreated from specialist seed suppliers and cool store them on arrival until conditions arerightforsowing.Usually,atemperatureof2–3°Cwillsufficeforgeneralseed storage, although some nurseries report good resultsat1–2°C,whichreducesthelikelihoodofseedsstartingtogerminateduringstorage.Formanyspecies,ambient storage using airtight containers kept in a cool place may also be used, as such seed can retain its viability for at least a year except under very adverse conditions.Controlledtemperaturestorageisadvisableforseedstobeheldforlongerthanoneyear.Therelationshipinstorebetweenmoistureandtemperatureiscritical.Manykindsofshort-lived seeds lose their viability completely if their moisture contentdiminishessignificantlywhileotherproblemsarise(notably,diseaseinfectionandspread)withincreasing moisture levels, so it is essential to strike therightbalance.Generally, reduced temperatures prolong the storage lifeofseedsandhelptooffsettheadverseeffectsofhighmoisturecontent.Usually,seedisstoredinsealed

polythenebagsorsmallsackstoreducemoistureloss.Some subjects require fresh seed for successful germination, for example, those belonging to the Umbelliferae family such as Ammi, Cenolophium and Selinum.

Seed germinationGerminationistheprocessbywhichanotherwisequiescent and viable embryo begins and progresses through the sequence of events that cause it to develop andestablishasanewplant.Itoccurswhenaseriesof required environmental factors coincide and are satisfactoryfortheprocesstoproceed.Fortheprocessof germination to be initiated and develop adequately, theseedwillrequireexposuretoanenvironmentinwhichthereis:

• Provisionofasufficient,non-limitingand suitablewatersupply

• An adequate and non-limiting atmosphere containing oxygen

• A suitable temperature regime

• Light (or lack of it if the seed is photosensitive) for photosynthetic activity, ultimately

Viable seeds that are exposed to the necessary environmental factors for germination and that still failtogerminatearesaidtobedormant.Germination,therefore,canonlybeachievedproductivelywhenthishasbeenovercomebyappropriatetreatmentwithleastlossofviability.More detailed information and guidance on seed propagation, including overcoming seed dormancy, can be found in the publication Hardy Woody Plants From Seed,byPhillipMcMillanBrowse.

Seed sowing in outdoor bedsOutdoor seed beds are mainly used by tree, forestry, rootstock and hedging producers but are also a useful techniqueforgrowingsmallquantitiesofrarerspecies.Easy germinating herbaceous subjects can also be sownoutdoors.Selecting the correct siteToensuregoodgerminationandgrowthofseedlings,the soils and site for outdoor seed beds should be chosencarefully.ThesoilshouldbefreedrainingbutmoistureretentivewithapHof5.5–6.5(towardsthelowerendforconifersandcalcifuges).Itshouldbeofmediumtextureandconditionedwithbulkyorganicmatterpriortousefornutritionandmoistureretention.Poorlydrainedsoilsandlowlyingsitesopentotheelementsshouldbeavoided.Thesiteitselfshouldbewellshelteredand,ideally,beofawarm,south-facingaspecttoencouragepromptseedgermination.Windprotection is especially important to protect seedlings frommoisturelossanddamage.Well-drainedsitesalsoenablepromptsoilpreparationandsowinginspring.


winter.Seedbedsitesshouldbeofawarm,south-facingaspect, wellshelteredandweedfree

Rotation of seedling crops is also vital, to maintain the soil fertility and reduce the possible build-up of soil-borne pests (for example, nematodes) and disease pathogens (such as Phytophthora and Verticillium).Site preparationLandshouldbefreeofweeds,especiallyperennialweedssuchasthistle,dock,bindweedsandcouchgrass;thesemustbeeradicatedwellinadvanceofsoilpreparations.Forresidualweedcontrol,thesoilfumigant‘Basamid’(dazomet)iswidelyused,appliedduringtheautumnforspringsowingsandthesummerperiodforautumnsowncrops.On heavy land, raised beds provide better drainage andareusuallypreferred,formedwitharidgingplough.The bed sides are usually trimmed so they slope gently inwards,toformabedaround1.5mwideatthebaseand1.2macrossthetop.Theheightofthebedisusuallyaround15cm.Bedsshouldbelevelledandfirmedandbase-dressedwithafertiliserinaccordancewithsoilanalyses.Soilsthathavebeeninproductionfor some time may only require a light top-dressing ofnitrogen,whilenewsitesareoftenlowinavailablephosphorusandpotassiumandsowillrequiremore. Afinalrakingandfirmingshouldthenbeprovided priortosowing.Ifthelandiswelldrainedandconditioned,thenraisedbedsarenotessentialbut,whereBasamidisused,thenthebedswillbepreformedbythetractorwheels,orthebedswillbemarkedoutwiththetractorwheelswhendrillingseed.Inpractice,ifthesoiliswelldrained,bedsthat are raised actually tend to dry out faster and so can bedetrimental.

SowingSeedsowingsareusuallymadeduringAprilandMay,sometimes a little earlier depending on the season and locality.Somesubjectsarebestsownduringtheautumnperiod,especiallythosewithshort-termlongevity,whichdeterioratequicklyiftheseedbeginstodryout.Subjectsthatusuallyrespondbettertoautumnsowingsinclude Aesculus, Castanea and Quercus.Populus and Salix also have a short-term viability and these seeds are best collected fresh (as soon as ripe), andsownimmediately.Fraxinus excelsiorcanbesown‘green’(beforetheseedhas ripened) but the resulting populations usually vary andcannotbeguaranteed.Therefore,theseedisbettertreatedandsubjectedtomoist,warmconditionsduringthesummerfollowedbycoldstratification,asthisenablesthedensityproducedtobemorecontrolled.Treatedseedisbestsownearlyinthespringbutcanbecoldstoreduntilconvenientandsownwhenthelikelihood of frosts has gone so avoiding unnecessary workinprovidingprotection.Seed can either be broadcast over the bed surface or sownindrills;thelatterenableseasierhandweedingandthinningofseedlings.Sowingindrillsalsolendsitselfwelltomechanicalandchemicalweedcontrol.

winter.Seedsowingindrills

Whilelargescalesowingsareusuallymechanised, handsowingswillsufficeforsmallerandmorevariedseedlots.Seedsizesandsowingdensitiesvaryandhandsowingprovidesgreaterflexibilityandcontrol.


Aftersowing,theseedshouldbegentlyrakedin,although in larger scale situations it is more usually lightlyrolledintothesurfacetomakecontactwiththesoil and reduce the amount of material required for covering.Whensowingdirectintodrills,theseediseithercoveredwiththeexistingsoilatthesametime orcoveredwithamaterialsuchasgritdowntherow;thisapproachusesverylittlecoveringmaterialcomparedtobroadcastsowings.Afterbroadcastsowing,seedareusuallycovered,generallywithafine,lime-free,gritorshingle,typically1.5–4.5mmsizegrade.Thedepthofcoveringdependsonthesizeoftheseedsbutisnormallyaroundtwice the depth of the seed (around 3 mm for small seeds andupto12mmforlargeseedssuchasacorns).Grit coverings are favoured as they provide good aeration, eliminate soil capping, enable easy removal ofweedsandevenpercolationofrainorirrigationwater.Perforatedplasticfilmsthatliftandopenasseedlingsemerge can also be considered (after the seed has beencovered)toencourageandprotectnewgrowth.Suchfilmsarewidelyusedintheproductionofsaladcropsandfieldvegetables.Each batch of seed should be labelled promptly after sowingwithawaterproofmarkerpen.Thelabel shouldrecordthefullnameofthesubjectsown,thedateofsowingandsourceoftheseed.Itshouldalsocross-referencewithanofficerecordofallsowings.Where only modest quantities of seed are involved, this canbesowndirectintopreparedbedsincoldframestominimiselosses.Suchframesprovidewinterprotectionandsummershade.Cultural workIrrigationmayberequiredaftersowing,especiallyifconditionsarewarmanddryandthesoilsurfacehasdriedoutduringpreparation.Irrigationundertheseconditionswillberequiredotherwisepoororunevengerminationwilloccur.Irrigationwillalsobeessentialthroughoutthespringand summer months during dry periods to enable germinationtotakeplaceandtosustainseedlinggrowth.Usually, irrigation is applied via overhead systems althoughlowlevelsystemssuchaslay-flatplasticcanalsobeconsidered.Summershadingofseedlingsisalsonecessary,especiallywithlarge-leavedsubjects,duringspellsofhot,brightsunshine.Shadenetting(1mhigh)supportedoverthebedsusuallysuffices.Crop protectionPestanddiseasecontrolwillrequireattentionduringthe spring and summer period, notably for aphids and caterpillars,anddamping-offandleafdiseasessuchaspowderymildew.Speciesshouldbegroupedtogetheratsowingtoaidpestanddiseasecontrol.Mice can be a particular problem and seed taken over longperiods,oftenwithnovisiblesignsofactivity,candrasticallyreduceseedlingpopulations.Miceandrabbitswillalsofeedonemergingseedlingswith

possiblebarkfeedingatthebaseintheautumn.Controlmeasuresneedtobetakenfromtheverybeginning.Birds can also devastate seed beds very quickly and some seed species are more susceptible than others (such as Corylus avellana, Fagus sylvatica and Pinus species).Damageisgovernedbythebirdpopulationandspeciesinthearea,coupledwithavailabilityofotherfoodsourcesatthetime.Largerbirds,suchaspigeonsandpheasants,andsmallerbirdslikefinchestendtodomostdamage.Fleeceornettingcanbeusefultoprotectcrops.Weedcontrolwillalsorequireattention.AlthoughtheuseofBasamidwillreduceannualweedsduringthefirstyear;bedsleftdownfortwoyearswillneedsomeformofchemicalorhandweedingtoenableseedlingstodevelopunhindered.Currently,lowrateuseofStompAqua (pendimethalin) and Goltix 70 SC (metamitron) can beusedviaoff-labelapproval(EAMU)forresidual weedcontrol.

winter.Powderymildewonfield-growncropsofAcer


NutritionA top-dressing of nitrogen may be required in midsummertoboostgrowth,dependingonconditionsandspecies.Thefrequencyandtypeoffertiliserrequiredthroughoutthegrowingperiodwillbegovernedby species, size requirement, seasonal conditions and thedegreeofirrigationused.Growthneedstobemonitored,somespeciesrequiremore nutrition than others and grouping these together willalsoaidcropmanagement.Withtheavailabilityofirrigation, it is often better to feed little and often as this reducestheamountlikelytobeleachedaway.Highpotashfeedsappliedinlatesummerwillhelptohardenplantsoff.UndercuttingIn order to improve the root structure of crops, particularlyonmineralsoils,seedlingsgrownonabedsystem can be undercut mechanically in summer or autumn,usingpurposelydesignedequipment.However,this should not be done during lengthy dry periods, and adequate irrigation should be on hand if such conditionsensuefollowingundercutting,otherwise,thecropwillsufferandinextremecasesbelost.Cropsthatareintendedtobegrownoneseasoninsitumaybeundercutonceortwiceduringthegrowingseason.Somecropsbenefitfromaveryearlyundercutting whentheplantissmallandlikelytohaveonlyproducedasingletaproot;thisstimulatesrootdevelopmentmuchearlierandatahigherlevel.Suchplantswouldnormallyreceiveafurtherundercuttingduringthesummer,belowthepreviousdepthbutabovethedepthatwhichthecropwillbelifted.Manycropsmayonlybeundercutonceduringthesummer,producingwhatissometimesreferred to as a ½-u-½ plant – a one-year seedling that hasbeenundercut.Seedlingsthatwillremaininsituforafurtheryearwouldnormallybeundercutduringlateautumnorearlywinterwhenconditionsaresuitable,producinga1-u-1(two-year)seedling.Whenseasonalconditionsareparticularlyfavourableforgrowth,undercuttingisalsoauseful crop management tool that can be used to check orslowgrowthdowntoregulateplantsize.Withplantsthat are to be planted or potted early (early autumn), undercutting10–14daysbeforeliftingwillhelpstimulatenewcellformationforenhancedrootdevelopment andestablishment.LiftingSeedlingscanbeliftedfromautumnonwardsfollowingspringsowing,eitherenmassewithanundercutterorselectivelybyhandwithforks,afterwhichtheyaretransplantedorcoldstoreduntilrequired.Alternatively,theycanbeleftinsituandgrownonforafurtheryear.Plants can quickly desiccate if left to dry out once lifted, particularly those still in green leaf and evergreen subjects.Particularcareshouldbetakentoavoidthishappeningviadampingmaterialdown,keepingmaterialout of full strong sunlight and transferring it promptly tocoldstorage.

Seed sowing under protectionA proportion of seed propagation is carried out under the protection of glass or polythene, for greater control andquickerthroughput.Manyherbaceousperennials,alpines and herbs, for example, are raised quite cheaply inthisway.Sometree,shrubandhedgingmaterialisalsoproducedinthisway.Muchoftheworkisnowautomated.Whilemorecostlythanoutdoororframesowings,thebenefitsofgreaterpredictability,enhanceduniformityandmuchspeedierthroughputoftenoutweightheadditionalcosts.Whilelowvalue,highvolumecrops can be produced readily and cheaply in outdoor seed beds,highvalueandtightlyspecifiedorscheduledcropsrequiretheclosercontrolofindoorsowings.Increasingly,seedraisedcropsaresownandgrownin plug trays to ease and speed up handling and meet the rising demand for year-round sales and planting material.Althoughonasmallerscale,wherelownumbersarerequired,itiseasiertosowintotraysratherthanintocells.Smallseed,suchasthatofmanyherbaceoussubjects,shouldbesievedpriortosowingtoavoidanyblockageofautomatedseederunits.

winter.Many subjects, including herbaceous perennials, can be easily raisedfromseedandsmallnumberscanbesownintrays


Growing mediaProprietary ready-mixed propagation media is often the preferredoptionforseedsowingdirectintoplugtrays.Crucially,itmustbewelldrainedbutmoistureretentive,flowableandeasytohandle.Suchmixesareusually peat-basedandcompriseawetter,limeforpHcontrol, alowlevelbasefertiliser(sufficientforbalancednutritionduringtheinitialsixweeks)andashort-termcontrolled release fertiliser in the form of mini-granules, toaiddistributioninplugtrays.Vermiculite,beinglightweightandsterile,isoftenincluded in seed propagation mixes too, largely on accountofitsusefulbufferingcapacity.Thereisalso some use of perlite to aid drainage and peat alternatives,notablycoirandfinegradebark.Linermixescanbeusedwhereseedissownintopots.Longer-term,cropswillrequiresupplementaryfeedingtomaintainquality.Seed sowingManycropsarenowmulti-seededintopotsorplugtraysviaanautomatedseederunit.Althoughseedqualityandviabilityarenowmuchimproved,itisvitalthat seed germination occurs in each pot or cell and produces a usable plant, hence, the practice of

multi-sowing.winter.Gritorvermiculitearewidelyusedtocoverseedsfollowingsowing

Itisalsodifficulttosowverysmallseedssinglybyhand.Usually,thesownseedsarelightlycoveredwithvermiculiteorgrit,toprotectthemandconservemoisture.Youngplantmaterialfortransplantingandgrowingonshouldbeadequatelyhardened-offbeforetransfertounheatedtunnels,glasshousesoroutdoornurserybeds.

winter.Manyspeciesarenowdirectlysownintomodulesofvarioussizes;deep cells are especially suitable for trees

Environmental controlSeeded pots and trays should be transferred promptly to the protection of a propagation house or frame for germination.ManyspringandsummersownHNSspeciesusuallyrequirelittlebywayofbaseheat,15–18°Cwilloftensufficewherenecessary,butwillrequire a stable environment, including protection from extremesoftemperature,lightandmoisture.Tothiseffect,potsandtraysaresometimescoveredwithalightweightfleeceorpolythenepropagationfilm,oncetheyhavebeensetdownonbedsorbenchestocreatesuchanenvironment.Supplementary lighting can also be used, for example, toacceleratethegrowthofwinterorearlyspringsownseedlingcrops.


Trays and pots require regular checking to ensure they don’tdryoutorbecomeoverlywet.Anysenescingfoliage,whichmayattractBotrytis, should be removed promptly.Checksshouldalsobemadeforearlysignsofdamping-off,afungaldiseasethatthrivesinthedamphumid environments of propagation situations and anysuspectseedlingsremovedimmediately.Periodicventingbyremovingthecoveringfilmoverpotsandtrays aids air movement and the dispersal of heavy condensation.Italsoenablesanynecessaryfungicidespraystobeapplied.Once fully germinated, plant material should be graduallyhardened-offinsidebeforebeingtransferredtoaframeorshelteredoutdoorbedforgrowingon.Earlyspringsowingsmayrequirefleeceprotectionagainstlatefrosts.

CuttingsAwiderangeofHNSspecies,includingherbaceousperennials and alpine plants, can be raised successfully from various types of cuttings, including those made fromsectionsofroot.Cuttingsarerelativelysimpletomakeandcanbepreparedandinsertedbylowcostlabourifwellsupervised.Inthecaseofhardwoodcuttings, this can also be done during the quieter wintermonths.Successwithcuttings,especiallythosedeemed tobeslowordifficulttoroot,dependson:

• Optimum timing

• The type of plant material used

• Howthematerialishandled

• TheenvironmentinwhichthecuttingsareplacedSoftwoodandsemi-ripecuttings,especiallyofthosesubjectsdeemedslowordifficulttoroot,usuallyrequire a more supportive, high humidity propagation environmentthaneasyrootingsubjectsorhardwoodcuttingstakenintheautumnandwinterperiod.

Types of cuttingsCuttingsareusuallycategorisedasfollows:

• Stemcuttings.Therearenumerousdifferenttypes of stem cuttings including nodal, internodal, heel andbasal.Theplantmaterialcanbesoftwood,greenwood,semi-ripeorhardwood,dependingonwhentheyaretakenandthephysiologicalconditionofthewood

• Leafandleaf-budcuttings.Thesetypesofcuttingsare usually formed from semi-ripe material

• Rootcuttings.Thesearenormallytakenduring the autumn to early spring period using dormant root sections

Many subjects can also be propagated by more than one of these methods, for example, Camellia (stem and leaf-bud cuttings) and many herbaceous perennials (stemandrootcuttings).Thechosenmethodoftendependsontheavailabilityofsuitableplantmaterial;

rootcuttings,forexample,arecheapandworkwellforsomespeciesbutmaybedifficulttoobtaininsufficientquantities.Theavailabletimeframeisanotherconsideration;terminalsemi-ripeshootcuttingsof Camellia,forexample,willmakeawell-branchedliner in six months, several months before one propagated fromleaf-budcuttings(typically,upto12months).

Stem cuttingsStem cuttings (made from shoot tips and sections of stem) remain the most commercially important method ofnurserystockpropagation.Suchpropagationisgenerallyfromsoftwoodandsemi-ripematerial.Stemcuttings can be nodal, internodal, heel or basal in origin dependingonthegrowthandrootingcharacteristicsofthesubjectandavailablematerial.Nodal and internodal cuttingsMost cuttings are nodal in nature in that they are cut belowthebasalleafjointduringpreparation,althoughmanysubjectsalsorootwellfrominternodalmaterial,wherebythecuttingissectionedorcutbetweentwoleaf joints, so making greater use of available cutting material.Climbers(singlenodeorleaf-budcuttingsofClematis and Hedera)canbepropagatedinthisway, ascanJapanesemaples(Acer palmatum cultivars) andmanyeasyrootingsubjectswithlonginternodessuch as Buddleia and Hydrangea.Often,bothnodal and intermodal cuttings are prepared from the same length of stem material to make maximum use of availablematerial.

winter.Several cuttings can often be made from the same section of stem material


.Close-up of typical nodal tip cutting

winter.Close-up of a typical internodal cutting

Heel cuttingsHeel or heeled cuttings are made by removing a young shoot (usually semi-ripe) from its parent plant withadownwardpull,bringingawayonitsbaseasmallpieceofolderwood,whichisthenusuallytrimmedpriortoinsertion.ItisdebatablewhetherHNSsubjectsrootanybetterwithaheelbutitcanbeaquickandeasywayofremovingcuttingmaterialfromparentstockwithminimalpreparation.Removingtheheelusuallyenableseasier insertion and better anchorage of the cutting in therootingmedium.

winter.Typical heel cutting, created by removing a young shoot from its parent

Basal cuttings (woody species)Stemcuttingsmayalsobebasalinnature,wherebythey are removed or prepared by cutting through or justbelowwhereayoungshootjoinsthemainstemorparentbranch.Usually,thereisaslightswelling(pulvinus) at this point and the knife is taken through thisorimmediatelybelowit,as,forexample,whenpropagatingfruitrootstocksbyleaflesswintercuttings.This also enables the cutting to be removed more easily fromtheparentplant.Suchmaterialissometimesreferred to as ‘grade 1’ because of its greater rootingpotential.Manyotherwoodysubjectspropagatewellfrombasalcuttings, notably cultivars of Acer palmatum, Exochorda and Syringa,especiallywhentakenearly,usuallyduringApril.Berberis, Cotoneaster and Hebe can also be propagatedinasimilarwaywhentakenassemi-ripebasalcuttingsduringthesummerorautumnperiod. Cotinus, too,respondswelltosoft,basalcuttings struckduringJuneundermistorfog.


winter.Close-upofatypicalbasalcutting;notetheswollenbaseatthepoint of removal from the parent shoot

Often,subjectscanberootedequallywellfromnodal,heel and basal cuttings, for example, species and cultivars of evergreen Berberis taken in September andOctober.Basal cuttings (herbaceous perennials)The term basal cutting is also used to describe cuttings removed from the base of clump forming herbaceous perennials such as Achillea, Aster, Delphinium and Phlox.Usually,thismaterialhasahighpropensityforrooting and so is especially useful for the propagation ofsubjectswhicharelessinclinedtorootfromsoftwoodcuttings, including Astrantia, Campanula lactiflora and Salvia nemorosa.Onsomeoccasions,suchbasalcuttingscomeawayfromtheparentplantwiththe rootsintact,ineffectformingmini-divisionsrather thantruecuttings.Softwood cuttingsThese are usually prepared from juvenile spring or earlysummernon-lignified(orripened)growthofmainlydeciduous but also some evergreen subjects during theApriltoJuneperiod.Typically,softwoodcuttings arequitesmall,nomorethan7–12cminlengthwith twoormoreleafjoints(nodes);cuttingsremovedfromshoottipscanbeusedformanysubjects.Propagation material harvested from stock plants or nursery crops should be removed just above a node to prevent die-back of ‘stubs’ and so in turn permit diseaseinfection.Acutshouldbemadebelowthenodeduringcuttingpreparationforthesamereason.Thelowerleavesareusuallyremovedtofacilitateeasier

insertion and subsequent support of the cuttings in the rootingmedium(althoughthisisnotalwaysnecessary).Very large leaves should be reduced in size to minimise waterlossandtomaximisethenumberofcuttingsperunitarea.Allflowerbudsshouldberemoved.Softwoodcuttingsarepronetorapidwaterlossandmustbehandledquicklyandwithparticularcaretoavoidbruisinganddesiccation.Theuseofshorttermcoldstoragetoremove‘fieldheat’andmaintain turgidityisbeneficialandimprovestherootingpotential.

winter.Typicalsoftwoodcutting,trimmedtoanode

HNSsubjectswidelypropagatedearlyintheseasonbysoftwoodcuttingsincludeAcer palmatum cultivars, Azalea (deciduous), Cotinus, Exochorda, Magnolia, Prunus (deciduous, notably P. incisa cultivars) and Syringa.Suchmaterialrequiresaparticularlysupportiveenvironmentandbenefitsfromtheuseofmistorhighhumidityfog,withbaseheatforrapidrooting.Awiderangeofherbaceousperennials,alpinesandherbs,arepropagatedbysoftwoodcuttings,including cultivars of Achillea, Delphinium, Helenium, Helichrysum, Helianthemum, Lamium, Lavandula, Nepeta, Penstemon, Phlox, Rosmarinus, Santolina, Salvia, Scabiosa, Sedum spectabile and Veronica.Typically, cuttings are quite short (5–7 cm) and removed fromclosetothecrownoftheplant.Suchmaterialcanoftenberootedreadilyatlowcostunderpolytheneormistwithoutbaseheat,directstuckintoplugtraysofvaryingsizes.Adequateshadingisessentialduringthesummermonths,particularlyintheabsenceofmist.While many subjects root readily and quickly from softwoodcuttingswithoutbaseheat,someoftheslowerandmoredifficulttorootspeciesdobenefit fromit.Initiallybetween18–21°C,reducinggradually asrootingoccurs.Althoughsoftwoodcuttingsarequiteresponsivetothe use of hormone rooting treatments, easy rooting


subjectsseldomrequirethemtorootwell.Ifconsiderednecessary,lowconcentrations(0.1%IBA)shouldbeused.Suchtreatmentsarelikelytobemorehelpfulforthe rooting of later struck material if the basal areas havebecomeripenedandalittlewoody,forexample,withlavenderandrosemarycuttings.Similarremarksapplytowounding.Whilebeneficialwithfirmer,semi-ripematerial,particularlyifhavingawoodybaseortakenwithaheelofolderwood,itisusuallyunnecessaryandoflittlevaluewithsoftwoodcuttings.Greenwood cuttingsGreenwoodcuttingsaretakenwhenthestemsareslightlyfirmeranddarker,particularlyaroundthe basalareabutnotsufficientlyfirmtobedeemed semi-ripeinnature.Itisnotawidelyusedtermbutisone that usefully indicates the idea that many subjects (including Deutzia, Fuchsia, Hypericum, Philadelphus, Potentilla, Spiraea and various herbaceous and alpine subjects)normallypropagatedbysoftwoodcuttingsalsorootwelloncethewoodhasgonebeyondbeingsoft.Assuch,theyaretakenslightlylaterthan softwoodcuttings,normallyduringthelatespring tomidsummerperiod.Cuttings are usually nodal or basal in nature, formed fromthecurrentseason’swoodandtypically8–10cminlengthwiththreeleafjoints.Softtipsareremovedandthebaseofthecuttinglightlywoundedwithasingleslice(2.5cm)tooneside.Usually,arootinghormone(0.1%IBA)isappliedtothebaseandthefoliageofveryleafycuttingsreducedinsizetominimisemoistureloss.Likesoftwoodcuttings,greenwoodmaterialrequiresquiteasupportiveenvironmentwithhighhumiditytomaintainfreshnessandreducewaterloss;mistorfogenvironmentsareideal.Baseheat(around18°C),whilenotessential,willaidrooting.Materialshouldbeshadedwellduringthesummer.Semi-ripe cuttingsSemi-ripecuttingsaremadefrompartiallylignifiedorripenedwoodtakenlaterintheseasonthansoftwoodmaterial,mostusuallyfrommidsummeronwardsusingthecurrentseason’sgrowth.Tosomedegree,theyareeasiertohandleandkeepfreshthansoftwoodcuttingsand many broad-leaved shrubs and conifers are successfullypropagatedinthisway.Normally,cuttingsare7–15cminlengthandoftenwoundedatthebasetostimulaterootinitiation.Theyaresometimesremovedfromtheparentplantwithaheelofolderwood,whichisthentrimmedwithasharpknife.Thebaseofthecuttingisusuallyquitefirm andripened.Rooting hormone products are often used and very largeleavestrimmedtoreducewaterlossandenablecloserspacingofthepreparedcuttingsintheirtrays.There is usually some removal of the bottom leaves to facilitate easier and quicker insertion of the cuttings intotherootingmedium.Shoottips,stemsectionsandthe basal portions of stems are used to make cuttings, withthebasalcutusuallybeingmadebelowanode.

winter.Typicalsemi-ripecutting,trimmedtoanodeandslidewoundedatthe base

Leafy semi-ripe cuttings also require rooting under conditionsthatminimisewaterlossfromleaves.Amist unit is ideal although polythene tent systems are commonlyused,particularlyfortheautumnandwinterrootingofevergreensandconifers.Close-contactpolythene(thingaugepropagationfilmlaiddirectlyover cuttings) can be considered but must be carefully managedtoensurecuttingsdonotbecometoowet. It is a relatively cheap system that remains popular intheNetherlands.Forsummerpropagation,whiteplasticisrequiredforshade,oftenaugmentedwithshadeclothabove,andin some cases, a shade paint applied to the roof of the glasshouseorpolythenetunnelaswell.Semi-ripecuttingsofmanyHNSspeciescanalso be rooted easily and cheaply in sun tunnels or cold frames, either in beds formed from prepared soil or rootingmedia,ordirectstuckintopots.These include cultivars of Azalea (evergreen), Buddleia, Deutzia, Forsythia, Hypericum, Philadelphus, Potentilla, species roses and Spiraea.

winter.Softwoodandsemi-ripecuttingstakeninmidsummerrequirerootingunderconditionswhichreducewaterstress


Hardwood cuttingsHardwoodcuttingsaremadefromhardenedorripenedwoodgenerallytakenfromthecurrentorsometimesthepreviousseason’sgrowthduringthedormantperiod,normallybetweenOctoberandlateFebruarytoearlyMarch.Itisusuallyadvisabletodefertakingsuchcuttingsofdeciduoussubjectsuntilafewweeksafterleaf fall because, up to that point, the stock plants are likely to contain high levels of abscisic acid, a naturally occurringplanthormoneassociatedwithleaffallthat islikelytoinhibitrootinitiation.For most trees and large shrubs, cuttings should be 20–30 cm in length, sometimes a little larger (up to 45 cm), for example, in the case of fruit tree rootstocks propagation to enable them to be budded clear of soil levelandontotheoriginalcutting.

winter.

Larger cuttings used to produce fruit tree rootstocks

Hardwoodcuttingscanalsobeusedtorootarangeof conifers, including cultivars of Taxus and various species of Abies, Juniperus, Picea, Pinus and Thuja.Suchmaterialrequiresdifferentpropagationconditionstoleaflesswintercuttings,notablytheprovisionofmoisturetoreducewaterlossfromleaves,hence,theuseofpolythenecoversormist.Thelattercanbecometoowetunlesscloselycontrolled.Well-ripenedwoodofmoderatesizeandvigourshouldbe used to ensure the cuttings have adequate food reserves in the form of carbohydrates to sustain root developmentandinturninitialshootgrowth.Shoottipsareusuallydiscarded;centralandbasalstemsectionsmakethebestcuttings.Normally,thecuttingscomprisestraightstemsectionsofusuallyone-year-oldwood.

winter.Leaflesshardwoodcuttingcomprisingripenedwoodtakenduringthe dormant period

Hardwoodcuttingsofbothdeciduousandconiferoussubjectsareusuallywoundedatthebasetovaryingdegreesandtreatedwitharootinghormonetohelpinitiateroots.Taxusappeartorootbestwhentaken withaheelofripenedwoodfromtheparentplant andwheninsertedintowell-drainedrootingmedia withsharpsandorgrit.Hardwoodcuttingscanberootedwithorwithoutbaseheat,dependinguponspeciesandavailablefacilities.Heated cutting bins are sometimes used for more difficulttorootsubjects,includingfruittreerootstocks.Manysubjectscanberootedwithheatedbenchesorbeds, including: Akebia trifoliata, Celastrus orbiculatus, Cytisus battandieri, Ficus carica, Fuchsia magellanica, Lonicera species, Metasequoia glyptostroboides, Parthenocissus, Polygonum baldschuanicum, Vitis coignetiae, Wisteria sinensis and Wisteria floribunda.Usually,basaltemperaturesof18–21°Csufficebut the tops of the cuttings need to be kept relatively cool (frost-freeorjustabove)anddrywithplentyofnaturaldaylight,notsubjecttomistorcoveredwithpolythene.Iftheairtemperatureistoowarm,budburstandshootgrowthwillensueattheexpenseofrootingandthecuttingswillperish.Rootingnormallyoccurswithinsixtoeightweeks.Cuttings can be inserted into deep plug trays or pots, larger cuttings can be inserted around the edgeofa2-litrepot.Biodegradablepotssuchas those formed from peat, coir or recycled paper can also be considered to minimise root disturbance andwastedisposal.For smaller shrubs and climbers, cuttings are usually nodal, 15–20 cm in length and inserted to about a third orahalfoftheirlength.Theyshouldbekeptwellairedandtherootingmediummoistbutnotwet.Rootedcuttingscanbespringpottedandgrownonunder protection before being moved outdoors during thesummer.Hardwoodcuttingsofmanywoodysubjectscanalsobe rooted cold, either in the open ground, under sun tunnelsorusingtraditionalcoldframes.Bushfruitssuch as blackcurrant and gooseberry, for example, rootreadilyinfieldsituations,asdoothereasyrootingspecies like Ligustrum, Populus and Salix, for hedging andspeciesrosesforrootstockproduction.


Shrub subjects such as Buddleia, Cornus, Deutzia, Forsythia, Philadelphus, Ribes, Sambucus, Spiraea and Weigelacanberootedwiththesimpleprotectionofacoldframe.Principalrequirementsaregooddrainage, natural light and adequate air movement to ensure cuttings don’t rot and attract disease pathogens such as Botrytis around the stems or Phytophthoraintheroots.

Leaf-bud cuttingsAlthoughnotwidelyusedcommercially,leaf-budcuttings are useful for the late summer and autumn propagationofsomeHNSsubjects,forexample,Mahoniawherethemorphologyoftheplantprecludesthe use of stem cuttings and Camelliawhereleaf-budcuttings are useful if propagation material is quite scarce.Onlystrongshootswithwell-developedbudsshouldbeused.Suchcuttingscompriseashortsectionof main stem cut just above a leaf joint and again betweentwonodes,resultinginasingleleafattached tothestemwithaleaf-budintheaxil.

winter.Leaf-budcuttingsmakeefficientuseofpropagationmaterial

Semi-ripewoodisusuallylightlywoundedand,whilerooting hormones can be applied, any treatment should beusedwithparticularcareduetotheproximityofthebudsthatcanbedamagedortheirgrowthdelayed.Some climbers, notably species and cultivars of Clematis are also propagated successfully from internodal leaf-bud or single node cuttings during springandsummerundermistorplasticwithbaseheat.

Root cuttingsMany subjects can be propagated cheaply and efficientlybysectionsofroottakenfromhealthyvigorouslygrowingstockplantsornurserycropsduringtheautumnandwinter,makingsaleableplantswithin12–18months.NotableexamplesincludeAcanthus, Ailanthus, Campsis, Clerodendron, Echinops, Eryngium, Paulownia tomentosa, Phlox paniculata, Rhus typhina, Romneya coulteri and Verbascum.Comparativelyunskilled labour can be used to prepare and insert the cuttingsifwellsupervised.Rootingpercentagesaretypicallyhigh,upto75%.

Rootsofpencilthicknessshouldbeselectedwherepossibleorslightlythickerforthosesubjectswithespecially thick roots such as Eryngium and Rhus typhina.Itisofteneasiesttoremovelongerlengths of root material and cut these into the desired length onabenchwithasharpknife.Sufficientrootshould belefttoenablestockplantstore-establishquickly.The roots of thick rooted subjects are usually cut intosectionsaround5cminlength.Unlikethinroots,they are usually inserted vertically and pushed into therootingmediumuntiltheirtopsarejustbelowthesurface.Toensurethecuttingsareinsertedthecorrectwayup,aslopingcutshouldbemadeatthetoporproximalendandaflatcutatthebottomordistal end;thetopofarootcuttingisalwaysthatpartthat isnearestthestemofthestockplant.Cuttingsshouldbe spaced around 7 cm apart or inserted singly into plugtrays.Thin roots are simply cut into 5 cm sections and laid horizontally on the surface of the rooting medium beforebeingcovered,usuallywitha1–2cmlayerofthemediummix.

winter.Thin roots are laid horizontally on the surface of the rooting mediumandcoveredoverwiththemediumorgrit

Cuttings can be directly stuck into beds, trays, plug trays or pots of standard rooting media and propagated in cold frames or a dry, frost-free location under glass or polythene.Goodmediumdrainageiscriticalandwhilebaseheat(12–15°C)isnotessential,itwillaccelerateroot development and help to minimise losses, as in thecasewithRomneya and Verbascum.Cuttingsareusuallycoveredwithalightweightfleeceorplastictoconservemoistureandretainheat.Usually,rootedmaterialisremovedfromMayonwardsbywhichtimethecuttingsshouldhaveformednewrootsandbegrowingaway.Rootedmaterialshould


be moved on as soon as it has formed satisfactory root systems.However,careisrequired,asrootcuttings,especiallythoseinwarmconditions,oftenproduce topgrowthbeforetheyhaverootedadequately.Once roots do emerge from the bottom of pots or trays, the plantsshouldbepottedandgrownon.Thoseraisedinheatwillrequirehardeningoffintunnelsoracoolglasshousefirst.

winter.Acanthusgrowingawayinsummer,followingearlyspringpropagation by root cuttings direct stuck into plug trays

Callus tissueOften the rooting of mainly semi-ripe cuttings is precededbythequitevisibleformationofwoundorcallustissue.Whilethisisawoundhealerandnaturalprecursor to root initiation, excessive callus inhibits rooting.Highbasetemperaturescantriggerthisproblem.Excess aeration in the rooting medium may also stimulate callus at the expense of root initiation (commonly seen in Camellia, X Cupressocyparis leylandii and Taxus species, for example), underlining thevalueofstrikingtherightbalancebetweendrainageandmoistureretention.Alkalineconditionsintherootingmedia exacerbate the problem by hardening the cells wallsintheouterlayer,somakingitverydifficultforyoungrootstopenetrate.Forplantmaterialinveryfree draining rooting media under open mist systems andirrigatedwithalkaline(hard)water,thiscanbeaparticularproblemasthepHoftherootingmediumrises.Excess callus formation is also caused by using cutting materialwhichisphysiologicallyunderdevelopedforrooting.Thisunderlinestheimportanceoftiming,particularlyinrespectofsoftwoodandsemi-ripecuttings.

MicropropagationMicropropagation is the isolation and culturing of small sections of plant tissue (an explant) in a sterile, carefully controlledenvironment.Usually,thesearemeristematic

tips but material may also be pollen, embryos or callus.Itisahighlyspecialisedtechniquedevelopedcommercially during the 1960s for the production of virus-free plant material, primarily Cymbidium orchids andlaterfruitrootstocks,strawberriesandNarcissus usingmeristemtipcuttings.Sincethen,therangeofHNSspeciesthatcanbesuccessfully micropropagated by specialist suppliers hasincreaseddramaticallyandmanyspeciescannowbeproducedinthisway.TheseincludeAlnus, Arbutus, Azalea, Betula, Buddleia, Clematis, Cordyline, Cornus, Cotinus, Daphne, Eucalyptus, Garrya, Hamamelis, Hebe, Hydrangea, Kalmia, Lavandula, Magnolia, Malus, Photinia Pieris, Potentilla, Prunus, Rhododendron (notably,difficulttorootYakushimanum hybrids), Rosa, Rubus, Skimmia, Syringa, Ulmus and Viburnum.An increasing range of herbaceous perennials can also be raised by micropropagation, including cultivars of Bergenia, Campanula, Cimicifuga, Crocosmia, Digitalis, Echinacea, Geranium, Helleborus, Heuchera, Hosta, Kniphofia, Leucanthemum, Lobelia, Nemesia, Papaver, Phlox and Scabiosa.Itcanalsobeusedforthepropagation of Anemone japonica cultivars to ensure freedom from leaf-bud nematode, a frequently common andseriouspestofthisplant.Several important bulb crops can also be raised this way,includingAnemone, hyacinth, Iris, lily, Narcissus, Nerine,snowdropandtulip,althoughinmostcasesonlytoincreasebreedingstock.Almostanyplantcanbemicropropagatedwithsomedevelopmentworkbuttheefficiencyofproductionvaries considerably so a more limited range is economicallyviableandcommerciallyavailable.The principal advantages of micropropagation are:

• The rapid clonal multiplication and so bulking up of slowordifficulttorootspeciesandnewcultivars

• The production and maintenance of high-quality, uniform, clean, virus-free plant material

• Year-roundpropagationofanincreasinglywidezrange of plants suitable for scheduled production for continuity of supply

Micropropagation also enables a large number of plants to be handled and transported at any one time, although this must be done carefully, as should the weaningofsuchmaterialpriortogrowingonundernurseryconditions.Thehygienicsoil-lessnatureofthe production process also means micropropagated materialcanbeexportedeasierthanplantsgrownbymoreconventionalmeans.Micropropagated plants can be easily transported and exported,onceweaned,aswell,andthisisoftenamorefoolproofwayforgrowerstoreceivematerial.Theprocessisveryspecialist,skilledworkandcanbedifficulttointegratewiththerestofthenursery.Italsorequiressignificantcapitaltoestablishtherequisitelaboratoryandweaningfacilities;evenasmalllaboratoryrequiressignificantspecialistequipment


costing£50,000–100,000.Labourcostscanalsobehigh, up to 80% of the total running costs and vary considerablydependingontheplantbeingpropagated.Including labour for bulking-up, overall production is, typically,25–50plantsperhour.

winter.MicropropagationisnowusedfortherapidmultiplicationofawiderangeofHNSsubjects

Geneticmutationsor‘off-types’mayalsooccur(astheycanwithconventionaltechniques)althoughthisis much more likely to arise from callus cultures than whereshootculturesareusedtomultiplymaterial.For this reason, callus cultures are avoided in commercialmicropropagation.Notallplantsrespondto micropropagation either and so must be increased byconventionalmeans,whichmaytakelongerandbeconfinedtospecifictimeperiods.Forthesereasons,micropropagationintheUKis nowundertakenbyspecialistproducerswiththenecessary expertise, facilities and equipment for commercialsuccess.

Culture mediumUsually, the culture medium comprises mineral salts for essential macro and micro elements, an energy source (usually in the form of sucrose), amino acids, vitaminsandgrowthhormones(notably,cytokininsforshoot formation and multiplication and auxins for root initiation)andagar(gellingagent)forsupport.Thebalanceoftheseelementswithinamediumvarieswithspeciesandcanvarybetweencultivarswithinspecies.Micropropagationspecialiststendtoformulatetheirownmediabasedonexperienceandthedifferingrequirements of the species involved but a limited range of‘ready-to-use’standardmediaareavailable.

EquipmentSterile conditions are essential to prevent infections of bacteriaorfungi,intheculturemedium.Allpreparationworkisdoneinalaboratoryandiscarriedoutunderasepticconditions,usinglaminarairflowcabinetsinordertoexcludecontaminants.The standard equipment required for tissue culture includesglassware,culturevesselsandanautoclaveforsterilisationoftoolsandculturemedia.Scalpels,sharp scissors, knives and forceps are used to handle, dividetheculturesandpreparethepropagules.Flamesterilisation or hot glass bead sterilisers are used for theirsterilisation.Prepared material is placed in jars or tubs on the culturemediuminanincubator,growthcabinetorgrowingroomtogrowataconstanttemperature,usuallyintheregionof20–25°CformostHNSspecies.Light is less critical at this stage and incubators are oftenonlylitbyasinglefluorescenttubepershelf,givingalowlightintensity.

Stages of micropropagationThe process of micropropagation usually comprises fivestages,thesearesummarisedbelow:Stage 0 – stock plant managementFor success, only high-quality clonal stock plants, whicharetruetotypeandofhighhealthstatus, should be used for the provision of propagation material.Stockplantsshouldbegrownunderclean,hygienic conditions and material should be taken at thecorrecttime,thatiswhentheplantsareactivelygrowing.Usually,container-grownplantsareused and brought under protection prior to propagation, to produce clean, fresh, vigorous, juvenile material suitableformicropropagation.Ideally,theyshould bewateredbylow-levelirrigationaswatersplashfromoverhead systems can readily increase the fungal and bacteriagrowthalwayspresentonplantsurfaces.Stage 1 – initiationThis stage consists of the establishment of plantmaterialinculture.Ensuringfreedomfromcontamination at this stage is critical, therefore careful surfacecleaningandsterilisationisessential.Exposuretimeshavetobecarefullyworkedouttominimisedamagetotheexplantmaterial.Only50%,andoftenless,ofthematerialinitiatedwillbecleanenoughtotaketostage2.Stage 2 – multiplicationThe rapid increase of material occurs at this stage, as theculturedmaterialgrowsrapidlyandproducesnewshoots,whichareroutinelydividedandtransferredtofreshmediaforfurthermultiplication(sub-culturing).Materialisgrownoninagrowthchamberuntiltherequiredquantityhasbeenobtained.Highlightlevelsare not required as micropropagated plants do not photosynthesise greatly at this stage, depending instead onthesugarsandnutrientsinthemediafornewgrowthandrootdevelopment.


winter.The multiplication process rapidly builds up plant numbers

Stage 3 – rootingSmall shoots are excised and transferred singly to afreshculturemediatoinduceroots.Usually,thisinvolvesmanipulatingthehormonebalance;highauxinto cytokinin favouring root development, high cytokinin toauxinfavouringshootproduction.Thisstageusuallytakesplaceinagrowthchamberorgrowingroom.Insome species, it can be omitted and shoots produced in culture, treated instead as soft cuttings and inserted intoarootingmediumwithrootinitiationoccurringduringweaning.Stage 4 – weaningWeaningistheestablishmentofplantletsingrowingmediafollowingmultiplicationinculture.Whenrooted,they are transferred to small pots or plug trays to establish.Thisstagecanbethemostdifficultandrequires a supportive, high humidity environment to ensurematerialdoesnotdryout.Thelackofawaxyleafcuticleonmicropropagatedmaterial(alongwithleafstomata being frequently locked open) means moisture islostmuchmorereadilythanwithconventionally raisedplants.Itisequallyimportantnottooverwateratthisstage,otherwisematerialwillquicklydeteriorateandbecomesusceptible to disease infection, notably Botrytis and damping-off.Shadeandadequatebaseheatprovisionarealsorequired.Usually,thisinitialweaningperiodlastsforaroundtwoweeks,afterwhichtheplantletsare transferred to a more open glasshouse or polythene tunnelforfurtherweaningbeforebeinghardened offforpottingandgrownonaslinersorsoldas weanedplantlets.Asaguide,HNSspeciesusuallyrequireintotalagradualweaningperiodofatleastonemonthbeforebeing subjected to a regular nursery environment and afurtherperiodoftwotothreemonthsofgrowingandhardeningoffbeforepotting.

Practical aspects of working with micropropagated materialInlaboratorysituations,growingroomsaregenerallyneithersuitablenorcost-effectiveforweaningand plantlets need to come out of their laboratory environment into gradually more natural conditions at somestage.Decidingwhenisthekey,becausewhileinitiation and sub-culturing are for the most part year-roundtechniques,rootingandespeciallyweaningaremorecloselyalignedtothenaturalseasons.Thisisparticularlysowithhardywoodyplantsandespeciallydeciduousspecies,whichenterdormancyasthedaylengthshortensandambienttemperaturesreduce.Plantsnotattherightstageofdevelopmentwillstruggletooverwinter.Toweanmicropropagatedplantsduringthewintermonthsandevenearlyspring,whichisagoodtimetoweanintermsofsupplyingplantsforpottinglaterintheseason,itwillbenecessarytousesupplementarylighting.Criticaltoweaningsuccessisforthepropagulestohave been given an adequate rooting period after sub-culturing(ifoneisrequired);ideally,thisshouldbedoneinaseparategrowingroomastherequisitetemperaturesoftendifferfromthoseoftheearlystages.The priority is to initiate adequate roots on each plantlet beforetheinitialweaningprocessstarts.Usingaseparate compartment also enables light levels to be gradually increased to harden the plant, notably by enablingtheleafcuticletodevelopgreaterprotection.Micropropagated plantlets have a particular anatomy, oftencharacterisedbyquitethinleavesfromwhichthenormalwaxycuticleislargelyabsentandwithfrequentlyopenstomata.Maintainingahighrelativehumidityaround the plants is therefore crucial, particularly during weaning.Evenduringthetransplantingprocess,leavescanbecomeflaccidandveryeasilydamagedby waterloss.Grading is important throughout micropropagation, otherwisemixedbatcheswillcomplicatecropmanagement,notleastwiththemovementofplantletsof varying sizes and stages of development through the differentstagesoftheprocess.Althoughmostnurseriesnowbuyintheirmicropropagation requirements from specialist producersasrootedcuttingsorweanedplantletsinplugtraysreadytogrowon,theymuststillbehandledwithgreat care during this critical phase, to ensure the young plantsneitherdryoutnorbecomeoverlywet.Nurseriesreceiving hardened plants should ensure they have been fullyweanedbeforedelivery.Very young plant material (especially stage 3 but alsostage4ifsemi-weaned)requiresparticularly carefulhandlingfollowingdeliveryandpriortopottingon.Itshould,therefore,begivenasupportivehighhumidity environment such as that provided by fog, polythene tents or mist units to ensure material does notdeteriorate.


Highhumidityenvironmentsmustbewellcontrolled, asitisparticularlyimportantnottooverwetthe plants.Well-managedfogsystemsusuallystriketherightbalanceandmaintainahighhumiditywithoutcreatingverywetconditions.Mistcansittoowetand tent systems require especially careful attention, althoughtheyarethecheapestmethod.Slitfilmscan beconsideredforhardierHNSsubjects.

winter.Semi-weanedplantletsrequireasupportiveenvironmentuntilestablished,fleecetentsmaintainthenecessaryhumidity

Anothercriticalaspectduringweaningistheprovisionof adequate shade from hot, bright sunshine to reduce waterlossandinturndeteriorationofyoungplantlets.Milky polythene should be used for tent systems and shadingforglasshouseswheremistorfogispreferred,althoughthelattertendstoproduceitsownshade.Additional net shading used and removed in accordancewithprevailingconditionsmayalsoberequired.Insummer,80%shademaybeneeded.Stage4plantmaterial,iffullyweanedandhardened, willonlyrequirealittlecarewithwatering.Adequate nutrition is also important throughout weaning,especiallywithplugtrays.Liquidfeedingprovidesflexibility,althoughlowrateminigranulecontrolledreleasefertiliserscanbeconsidered.

winter.A batch of micropropagated Heuchera,fullyweaned

Improving liner growth and quality post-weaningWhilemostmicropropagatedmaterialgrowsawaysuccessfullyonthenurseryfollowingweaning,somecropscanposeparticularproblems.InthecaseofKalmia and Betula, premature dormancy can occur duringthegrowingseasonwhenenvironmentalconditionsaresuitableforgrowth,whilewithDaphne poorbranchingcanleadtomisshapenplants.Betula plants can enter premature dormancy if subjectedtoaperiodofcoldgrowingconditions;socareneedstobetakentoavoidlatespringcoldspells.This dormancy can only be broken by a cold treatment ofsixweeksat4°C.Daphne odora ‘Aureomarginata’ and Daphne cneorum arenaturallyslowtobranch(usually,thisoccurspost-flowering)andoftendothishigherupthestem,creatinganunbalancedappearance,lessattractiveforsales.AHDBHorticultureprojectHNS32:Factors controlling the quality of micropropagated HNS liners, sought to better understand the factors responsible for poor liner growthfollowingweaning,usingKalmia and Daphne asexamplesofsuchproblems.Theworkfocusedonboth the procedures adopted during micropropagation andhowthesemayaffectsubsequentgrowth,andthenurserypracticesthatcouldbeadoptedfollowingmicropropagationtoimprovegrowth.


Case study 3: Micropropagation Services (EM) Ltd Micropropagation – a view from the laboratoryNealandBarbaraWrightsetupMicropropagationServices Ltd near Loughborough, in Leicestershire, in1985.Thefamily-ownedbusinessisnowoneoftheUK’sleadingsuppliersofyoungplants,producing over a million each year, mainly from micropropagationbutalsofromseedandcuttings.The plant range produced includes shrubs, roses, climbers, ericaceous subjects, blueberries, herbaceous perennials and trees for amenity and woodlandsituations.Popularlinesincludegroundcover roses, herbaceous perennials and Betula jacquemontii.Graded,fullyweaned(stage4)plantsaredespatchedtocustomersinpreformedEllepots.DirectorNealWrightsummarisesthebusiness:“Increasingly,weseeourselvesasacompleteyoungplant supplier as distinct from a purely lab-driven one.Asthebusinesshasevolved,ithasbecomeclear to us that, to be viable and competitive, weneedtobeflexibleandnotfocuspurelyonmicropropagation.Inmanyways,micropropagationand conventional techniques mesh together verywell,requiringsimilar,protectedgrowingenvironmentsthatarewellcontrolled.However,forthistowork,thelaboratoryandnurseryfunctionshavetobewellintegrated.Itmustalsobeforwardplannedandwellorganised;micropropagationattractshighlabourcosts,soefficientworkingisimportant.“Thoroughweaningiscrucialtoo.Weprefertodespatch stage 4 rather than stage 3 material as thelatterismorevulnerableandsomoredifficult forgrowerstohandle.SomeHNSsubjectswean

easier than others, for example, herbaceous perennialsareusuallyquitestraightforward,whilemostofthewoodyspeciescanbequitedifficult.Weusesupplementarylightingforwinterandearlyspringweaning.“Most of our propagation occurs during the spring andsummerperiods,whenstockisinactivegrowth,withcropsweanedandoverwinteredforspringandsummersalesthefollowingyear.”For crop protection, the nursery prefers to use biopesticides such as Serenade ASO, for example, to control BotrytisandMet52forvineweevilcontrol.Good cultural practice, including maintaining high levelsofnurseryhygienearealsoimportant.Drenchtreatments of the microbial inoculant products Revive and Trianum are also used to help prevent rootdiseasesandstimulategrowth.Nealcontinues:“Our customers require reassurance about vine weevilcontrolsoweincorporateproductstodealwithit.Wealsouseabespokegrowingmedia(75:25peattobarkwithbaseandcontrolledreleasefertiliser)andmakeourownEllepotstogiveusaddedflexibilityandqualitycontrol.”

winter.Plantmultiplicationunderway

Overcoming premature dormancy ThefollowingwerekeyfindingsforKalmia from the project:

• Maintainingshootgrowthbyearlyandregularliquidfeeding, increasing the frequency as the plant develops and is potted on, helps overcome premature dormancy

• Usingsupplementaryheatingoverwinterhelpstoboostsubsequentgrowthandbranchingoflinerswhencombinedwithliquidfeeding

• Prematuredormancyduringthegrowingseasonmaybebrokenbysubjectinglinerstofourweekschilling at4°C

Improving lateral branching In the case of Daphne:

• Shoot production and lateral development may be induced during micropropagation but at the expense ofrootingandplantvigourduringearlyestablishment.

Daphne species are very sensitive to cytokinin concentrationandmayrequiredifferentconcentrationstoachievetherightbalance;differenttypes of agar may also promote further variation

• Growingyoungplantsoverwinterwithheatingandsupplementary lighting promotes better branching andmoreearlyflowering.Recentlyweanedplantsare more responsive than older ones

• Pruningweanedmaterialcreatesalowerframeworkbutshouldbedonewhenplantsaredormant,sothatapical dominance doesn’t restrict branching, timing iscrucial.WhileDaphne cneorum cultivars can be prunedinthiswayoncewellrooted,subsequentvigourandestablishmentmaysuffer,sopruninginearly spring is more appropriate

Thesefindingsarelikelytohavebroaderapplicationstoother crops that display premature dormancy or a lack ofearlybranching.


Case study 4: Seiont NurseriesMicropropagation – a view from the nurserySeiontNurseriesnearCaernarfoninWalesproduces1.2millionyoungplantsayear,comprising300,000plugsand900,000potliners,dividedequallybetweenherbaceous perennials (notably, Agapanthus, Hosta and Heuchera) and various shrubs (mainly Physocarpus, Sambucus and Sorbaria).The nursery had considered using a high humidity fogenvironmenttoweanmicropropagatedmaterial(usually bought in as stage 3 rooted cuttings for prickingoutorstage4weanedplantletsforlinerpotting) but opted for mist, managed carefully withtheexpertiseofexperiencedstaff.Fleece,asa temporary tunnel cover over pricked-out stage 3 micropropagated material, provides shade and reduceswaterstressontheyoungplants.Oncebulkedupbymicropropagation,newlinesareusuallypropagatedbyconventionalcuttings.VarietiesthataredifficulttoweansuchasHeuchera ‘MidnightRose’areboughtinasastage4weaned

plantlettoeaseestablishment.“Ourusualdrillwithstage3material,”saysNeilAlcock,NurseryManager,“isfollowingprickingoutintoplugtrays(40% coir, 30% peat, the balance comprising vermiculite and perlite), the young plants are misted andcoveredwithfleece.Ahalf-ratefungicideisused to protect young plants from disease infection whiletheyareestablishing.”Neilgoesontomentionthatsuccessfulweaningmeans “planning your production so that propagation material is not all arriving at the sametime,especiallymicropropagatedmaterial.Schedulereceiptofdeliveriesearlyintheweekwherepossible.Weantrickyvarietiesinhighlyvisiblenurserylocationstohelpmonitoring.Getmicropropagated plants pricked out into plugs as soonastheyarriveonthenursery.Don’tletthemhangaround;thetransportofstage3materialisdamaging enough, they are using up reserves all thetime.Weanlargebatchesofmicropropagatedmaterial in spring rather than during the heat ofmidsummer.”

Improving the quality of HNS plants raised by micropropagation via pinchingThequalityoffinishedplantsisofteninfluencedbypinchingorpruningtreatmentsappliedtoweanedplantletsandlinersbeforepottingon.AHDBHorticultureprojectHNS40a:Optimising pruning of micropropagated and conventionally propagated container-grown plants,lookedattheeffectofdifferentpinchingtreatmentsonmicropropagatedRhododendron.Treatments included early or late pinching (removal ofthegrowingpointandtop2–3leaves)ofweanedplantletsinplugtraysorapinchafterpottingon.Theworkwithmicropropagatedmaterialfocusedoncultivars of Rhododendron yakushimanum (‘Percy Wiseman’, ‘Titian Beauty’, ‘Sleepy’, ‘Hoppy’, ‘Venetian Chimes’ and ‘Silver Sixpence’) and a single hardy hybrid (‘PinkPearl’).

Treatmenteffectsvariedwithcultivar,whichintermsofresponsecouldbebroadlycharacterisedasfollows:

• Those that branch naturally and require little if any pinching either in the plug tray or after potting, e.g.‘TitianBeauty’

• Those that require pinching, in the tray to stimulate branching,e.g.‘PercyWiseman’

• Those that require pinching in the tray and after pottingtodevelopagoodbranchframework, e.g.‘PinkPearl’

The Rhododendron yakushimanum hybrids tended to branch more freely than the more vigorous hardy hybrids.Anearlypinchintheplugtrayappearedespecially important in encouraging branching of the Rhododendron yakushimanumhybrids.Someimprovement in branching of the hardy hybrid ‘PinkPearl’wasachievedbyadoublepinch.

Well-rootedweanedplantletsofHeuchera


Grafting and buddingGrafting and budding techniques are fundamentally the same procedure, namely that of joining a scion varietytoacompatiblerootstock;somuchso,that thetermgraftingoftenincludesbudding.Individualcultivars can be propagated by either or both techniques depending on the time of year (dormant orgrowingseason),method,environmentalconditionsandmaterials.Therearenohardandfastrulesandindividual nurserymen have developed many minor variationsonthebasicprinciplesdescribedbelow. Both methods are vegetative propagation techniques, usedwhereotherpropagationmethodsarelesssuccessfuloruneconomical.PioneeringworkintheUKatNIABEMRandLongAshtonResearchStationsbetween1940and1990introducednewselectionsofrootstocksforfruittreesthatprovidedawidevigourrange,includingthereleaseofthefirstvirus-freematerialofbothrootstockandscionvarieties.Furtherworkwastocontinue,withsomeclonalrootstockselection of Acer platanoides and Tilia cordata amenity rootstocks, and the very successful commercialisation of ‘chip’buddingthatnowdominatesfruitandornamentalfieldproductioninmanycountries.Grafting can be used both in the open ground and under protection at various times of the year for the moredifficultsubjects,whilebuddingisgenerallyusedinfieldproductionduringthegrowingseason,onrelativelyeasysubjectsandwherepropagationspeedandeconomicuseofpropagationmaterialareapriority.All grafting and budding methods share the same principle of uniting the cambium layer of scion and rootstockaccuratelytoformastrongunion.Compatibilityofscionandrootstockisvitallyimportant.Therearenumerous simple and quite intricate grafting techniques andthemostcommonandeffectiveofthoseusedinmodernpropagationaredescribedinthissection.There are several economic and practical reasons for grafting or budding, notably:

• Itisanimportanttechniqueforplantsthatwill notrootwellfromcuttings.Rootstockshaveawell-developedfibrousrootsystemtoquicklysupporttherapidformationofcallusbetweenrootstock and scion, eliminating the loss potential of other rooting techniques

• It enables saleable plants to be produced more quickly.Therapidgrowththatresultsfromthecarbohydrate reserves in rootstocks produces vigorous straight stems and maximum girth early in the tree production cycle

• Ithelpscontrolplantvigour.Inparticular,fordwarffruittreesinmodernorchardsandgardens,wherevegetativegrowthisreducedandfruitproductivityisincreasedatthesametime.Lowvigourrootstocksfor Malus and Prunusarenowbeingconsideredforamenity use to reduce the size of trees in urban street planting

• Itisusefulwherespecialgrowthformsarerequired,asin,forexample,thetop-workingofstandardorweepingtreesand,conversely,theproductionofdwarfplants

• Itcanpromoteearlierflowering.Dwarffruitrootstocksinparticularhaveaninfluenceontheformation of early fruit bud

• It is a useful nursery technique for spreading workloads.Withtheuseofcoldstoragetoextenddormancy of both scion and rootstock, nurseries are nowabletospreadouttheirpropagationprogramme

In terms of the equipment required for grafting and budding, make sure good quality knives made of hard steelareusedandaresharpenedtoakeenedge.Asgrafting is a form of precise carpentry, the very sharpest ofbladeswillmakeallgraftingmotionseasierandresultin smooth cut surfaces for quick and healthy callus formation.Itisbesttofinishthesharpeningofthebladeonaleatherstroptoensurethesharpestofedges.Varioushandandpowerassistedgraftingmachineshavebeencreated;mostarequiteusefulifscionandrootstockmatchexactly.However,inreality,thismatch isdifficulttoachievesotheskilloftheknifemanisthekeytoagood‘take’.As for knives, secateurs need to be clean, sharp and wellmaintained.

winter.Aselectionofknivesusedforbuddingandgrafting,thetoptwoare used for ‘T’ or chip budding, the curved blades for grafting largecalibrerootstocksandscionwood,whilethebottomthreeare suitable for bench and rind grafting


Tying materials, the methods used and the timing of removalTying materials come in either degradable or non-degradableforms.Degradablerubberofmanydifferingwidthsandgradescanbeused,including‘patches’specificallymanufacturedforrosebuddingthatareheldinplacewithawirestaple.Ingeneral,stripsorrollswherematerialisself-selectedbylengthare the most common tying materials for grafting and chipbudding.Degradabletiesareconvenientandrecommendedfortheeasiersubjects.

winter.Bud patches made from degradable rubber are normally used when‘T’buddingroses

Non-degradablepolytheneandnowmoremodernstretchable self release laboratory materials are all used bynurserymen.Non-degradabletiesarereliableastheycanbereleasedatagiventimeandofferthepropagatorprecisecontrolduringthecrucialweaning-offperiod.

winter.Non-degradablepolythenebuddingtapeiswidelyused whenchipbuddingandprovidescontrolduringthecriticalweaning-offperiod

All tying methods have the same golden rule, to be firmenoughtostopanywaterpenetrationandtoencouragecallusquicklybutnottobetoofirmso astoconstrictgrowth.The removal of non-degradable ties should take place once callus has formed, usually after approximately 4–6weeksandbeforeanyconstrictiontakesplaceduetoexpansionoftherootstock.Itisalsonecessarytobeawareoffungalinfectionsthatmaydevelopbeneaththetieiftheyremaininplacetoolong.Ifremovingtieswithasharpblade,thebarkmustnotbeinjuredinanywayanditisbesttocutawayfromthestem.

Wax and waxing equipmentColdandhotwaxesareusefultocoverthegraftunionwhererubbertiesareusedandforsealingthesciontopcutsurfaceorasadippingwaxforthewholegraft.Thelatterrequiresahotwaterheatercompletewithanaccuratethermostat.Itisrecommendedthatwaxtemperaturesdonotexceed75°C.Waxcomesinmanypurposemadepreparationsbasedonparaffinwaxes,withadditionalsoftenersandoccasionalfungicides.

Equipment hygieneThiswillbediscussedingeneraltermsthroughout this section but regular sterilisation of the cutting surface of knives and secateurs prevents the spread ofharmfulpathogens.Methylatedspirits,weak solutions of domestic sterilants or other preparatory productsareexamples.

RootstocksSources and age of rootstocksSpecialistrootstockgrowersareagoodsource forawiderangeofseedlingandclonalrootstocks.Certain selected seed sources are usually earmarked |for rootstocks and it is important to discuss the optionswiththesupplyingnursery.Dependingon thepropagatorspreference,eitheroneyearortwo year-oldrootstocksareused.Universalcodingintradecataloguesisusefultoknowandthefollowingareused:

• 1+0 (1 year)

• 1+1 (1 year then transplanted for a further year)

• 1-u-1 (2 year undercut but left in situ for the second year)

• 1+2(1yeartransplantedandgrownonfor2years)• 2+0 (1 year)

• 2+1 (2 year then transplanted for a further year)The above codes cover both seedlings and clonal rootstocksgrownfromlayersorstoolbeds.Rootstock gradesItisimportanttoknowtheparticulargrade(girth)thatisrequiredforthetypeofgrafttobeemployed.Forthepurposesoffieldbuddingaplantinggradeof5–7mmor7–9mmisideal,withtheexpectationthatatthetimeofbuddingthisrootstockwillbeintheregionof8–12mm tomatchsuitablebudwood.


winter.Potted rootstocks of Acer palmatum cleaned and ready for grafting

Aknowledgeofthepreferredpotsizeandtheexpectedgrowthrateisimportanttojudgethesizeoftherootstocktobepurchasedifpot-grownrootstocksaretobeusedforwinterorsummergraftingafteronegrowingseason.Bare-rootgraftingiseasiertoservicebyorderingtheexactcalibreofstockrequired.Scionwoodcanbeextreme,fromthatoftheverythinAcer palmatum material used for summer grafting to much broader Aesculusmaterialusedforwinterbare-rootbenchgrafting.Clonal rootstocksThe advantageous properties of clonal rootstocks havebeenmentionedearlierandtheyshouldalwaysbe considered in preference to seedling raised material whereavailable,notonlyforincreasingthesuccessratesingraftingbuttoimprovetheuniformityofgrowthinthenursery.

Scion woodKnowledgeoftheprogenyoftheparentmaterial,itsconfirmedidentityandtheaccuracyoflabellingandrecords are all important before the collection of scion wood(orbudwoodintermsofbuddingmaterial)begins.Sources of materialItisquiteacceptabletotakescionwoodfromsaleableproduction trees or shrubs as it is very often healthy andjuvenile.Allscionwoodshouldbeofone-year-oldmaterial(ofcurrentseason’sgrowth).However,therearemanyadvantagesofhavingestablishedstockplants.Largequantitiesofscion woodcanbeharvestedefficientlyattherighttime andinadedicatedstockarea.

winter.Well-managedstockplantsenablelargequantitiesofscionwoodto be harvested at the optimum time

Health statusPests, diseases and virus infections can all be transferred during the multiplication process, so vigilance is required to maintain clean stock material.Closevisualinspectionsshouldbeongoingthroughoutthedormantandgrowingseasonswithadditionallaboratorytestingtoconfirmanysuspicioussymptoms.Modernmoleculartestsarenowavailablefor basic virus infections and batch tests can be done quiteeconomically.Collection and storageAll budding and grafting success rates are maximised ifscionwoodiscollectedswiftly,keptcold(3–4°C) andwellwateredtomaintainmoisturelevels.Soft shoot tips and mature basal stem areas should bediscardedand,inthecaseofscionwood,leaves on the remaining section trimmed to leave short petioles.Usually,thebudsticksarethenbundled andlabelleduntilrequired.For summer grafting, some propagators prefer to retainsomeleavesonthescionwoodifacoveredgraftingcaseofsomesortistobeused.Maintaining thegraftsinamoistenedstateisessential.Forwintergrafting,thesamecoldstoretemperatures (3–4°C)shouldbeusedandscionwoodshouldbewrappedtopreventdesiccation.Itisadvisabletocollectscionwoodfrommid-December(afterleaffall)andthroughJanuarybutonlyonfrost-freedays,ascelldamagecanoccuriffreezingorbelow.Itisadvisableto collect some subjects such as Acer and Betula early (December) to prevent heavy sap bleeding from mothertrees.


winter.Scionwoodshouldbecollectedswiftly,keptcoldandbewellwateredforoptimumresults

Winterscionwoodcanbestoredinpolythenebags inacoldstoreforupto8–10weeks.Alternatively,it can be stored in co-extruded bags, black on the inside,whiteontheoutsideonaconcretefloorin acoldshedorbarnforseveralweeks.Forconifers and other evergreen subjects, it is best to collect andgraftstraightaway.

Rootstocks and scion compatibilityCompatibilitybetweenscionandrootstockcanbe acomplexsubjectifoneexaminesthewideroptionsavailable.Insomecasesitispossibletousedifferentspeciesofrootstockandscionandobtaingoodresults.OneexamplewouldbeintheRosaceaefamilywhereAmelanchier, Crataegus, Malus, Pyrus and Sorbus are ofteninterchangeable.However,forsimplicity,itisbesttobecautiousandusetriedandtestedcombinations.Table 9 (overleaf) provides guidance on the most commonlyusedcombinations.

Symptoms of incompatibilityArangeofsymptomscanbeassociatedwithincompatible graft combinations including:

• Failure to form a successful graft union in the case of a high percentage of the grafted crop

• Differencesingrowthratebetweentherootstockandthe scion

• Overgrowthsaroundthegraftunion• Breaking of the graft at the union

• Prematureleafabscissiontowardstheendofthegrowingseason

• Decline in vigour and extensive shoot death in the grafted crop

• Prematuredeathofplantsafterayeartotwofollowinggrafting

Successful scion and rootstock graft union


Table9.Commonlyusedrootstockandscioncombinationsforgrafting

Rootstock Scion examples

Abies alba Abies koreana ‘Silberlocke’, Abies lasiocarpa ‘Compacta’

Acer campestre Acer campestre ‘Carnival’, Acer campestre‘WilliamCaldwell’

Acer negundo Acer negundo ‘Elegans’, Acer negundo ‘Flamingo’

Acer palmatum Acer palmatum ‘Garnet’, Acer palmatum ‘Osakazuki’, Acer japonicum ‘Aconitifolium’, Acer shirasawanum ‘Aureum’

Acer platanoides Acer platanoides‘CrimsonKing’,Acer platanoides ‘Drummondii’

Acer pseudoplatanus Acer pseudoplatanus ‘Simon-Louis Freres’, Acer pseudoplatanus ‘Brilliantissimum’

Amelanchier lamarckii Amelanchier ‘La Paloma’, Amelanchier‘R.J.Hilton’

Betula pendula Betula utilis‘GrayswoodGhost’,Betula nigra ‘Heritage’, Betula pendula ‘Tristis’, Betula albosinensis ‘Red Panda’

Carpinus betulus Carpinus betulus ‘Fastigiata’, Carpinus betulus ‘Frans Fontaine’

Catalpa bignonioides Catalpa bignonioides ‘Aurea’, Catalpa x erubescens ‘Purpurea’

Cedrus deodara Cedrus atlantica ‘Glauca Pendula’, Cedrus deodara ‘Aurea’

Cercidiphyllum japonicum Cercidiphyllum japonicum ‘Pendulum’

Cercis canadensis Cercis canadensis ‘Forest Pansy’, Cercis chinensis ‘Avondale’

Cornus kousa Cornus kousa ‘Wisley Queen’, Cornus ‘Eddies White Wonder’

Corylus avellana Corylus avellana ‘Contorta’, Corylus avellana ‘Red Filbert’

Corylus colurna Corylus colurna ‘Te Terra Red’, Corylus avellana ‘Contorta’

Cotoneaster bullatus Cotoneaster ‘Cornubia’, Cotoneaster ‘Hybridus Pendulus’

Crataegus monogyna Crataegus laevigata ‘Pauls Scarlet’, Crataegus persimilis ‘Prunifolia Splendens’

Fagus sylvatica Fagus sylvatica ‘Riversii’, Fagus sylvatica‘Dawyck’

Fraxinus excelsior Fraxinus angustfolia‘Raywood’,Fraxinus excelsior‘Jaspidea’

Ginkgo biloba Ginkgo biloba ‘Autumn Gold’, Ginkgo biloba ‘Princeton Sentry’

Gleditsia triacanthos Gleditsia triacanthos ‘Sunburst’, Gleditsia triacanthos ‘Ruby Lace’

Hamamelis virginiana Hamamelis mollis ‘Wisley Supreme’, Hamamelis x intermedia ‘Barmstedt Gold’

Juglans regia Juglans regia ‘Broadview’,Juglans regia ‘Franquette

Laburnum anagyroides Cytisus battandieri ‘YellowTail’,Laburnum x watereri ‘Vossii’

Ligustrum ovalifolium Syringa vulgaris ‘Esther Staley’, Syringa vulgaris ‘Sensation’

Liquidambar styraciflua Liquidambar styraciflua ‘Worplesdon’, Liquidambar styraciflua ‘Slender Silhouette’

Liriodendron tulipifera Liriodendron tulipifera ‘Fastigiatum’

Magnolia kobus Magnolia sprengeri ‘Claret Cup’, Magnolia ‘Apollo’

Malus ‘Bittenfelder’ Malus tschonoskii, Malus yunnanensis ‘Veitchii’

Malus M9 Eating apples

Malus M25 Malus tschonoskii, Malus yunnanensis ‘Veitchii’

Malus MM106 Malus floribunda, Malus ‘Rudolph’ and eating apples


Table9.Commonlyusedrootstockandscioncombinationsforgrafting(continued)

Rootstock Scion examples

Nyssa sylvatica Nyssa sylvatica‘WisleyBonfire’

Picea sitchensis Picea pungens ‘Hoopsii’, Picea omorika‘Nana’

Pinus contorta Pinus sylvestris ‘Chantry Blue’, Pinus mugo ‘Winter Gold’

Pinus strobus Pinus parviflora ‘Glauca’, Pinus strobus‘Nana’

Prunus cerasifera Prunus x blireana, Prunus cerasifera‘Nigra’

Prunus ‘Colt’ Prunus ‘Shirofugen’, Prunus‘Kojo-no-mai’

Prunus ‘Gisela 5’ Eating cherries

Prunus avium Prunus ‘Shirofugen’, Prunus‘Kojo-no-mai’

Pyrus communis Pyrus salicifolia ‘Pendula’, Pyrus calleryana ‘Chanticleer’

Quercus cerris Quercus castaneifolia ‘Green Spire’

Quercus robur Quercus robur‘Koster’,Quercus frainetto‘HungarianCrown’

Quince A Pyrus ‘Conference’, Pyrus ‘Doyenne du Comice’

Rhododendron ‘Cunningham’s White’ Hardy hybrids, Yakushimanum hybrids

Rhododendron ‘Inkarhro’ Hardy hybrids, Yakushimanum hybrids

Robinia pseudoacacia Robinia pseudoacacia ‘Frisia’, Robinia hispida

Saint Julien A Plums, gages, damsons, apricots, nectarines and peaches

Sorbus aucuparia Sorbus‘PearlyKing’,Sorbus ‘Autumn Spire’

Sorbus intermedia Sorbus aria ‘Lutescens’, Amelanchier ‘La Paloma’

Tilia cordata Tilia cordata ‘Greenspire’, Tilia cordata ‘Winter Orange’

Tilia platyphyllos Tilia americana ‘Redmond’, Tilia petiolaris ‘Brabant’

Viburnum opulus Viburnum x burkwoodii‘Mohawk’,Viburnum carlesii ‘Aurora’

Wisteria species Wisteria sinensis‘Prolific’,Wisteria floribunda‘Lawrence’

Types of graftThe common methods of grafting and budding are describedbelow.Therearetwoprinciplegraftingtechniques.

• Apicalgraftwherethescionandrootstockarejoined at their ends

• Sidegraftwherethescionisinsertedinthesideof the rootstock

The length of the individual scion is a matter of grafters’ preference.Havingtwotothreebudsexposedafterthegrafthasbeentiedandsealedisnormal.Thisallowsforback-up shoots in case of damage and the graft itself contributesitsownstoredreservestothecallusingprocess.Ifthesubjectisrelativelyeasyandthereisa shortage of scion material, the grafter can elect to ‘graftoffthestick’,thatiswithoutpreparingindividualscions.Inthiscase,ashortgraftcanbeused.Figure7summarises the most commonly used apical and side graftmethods.

A crop of recently side-grafted Quercusshowingrootstockandscion


Apical grafting

Bench grafting

Whip or splice graft, cleft or wedge graft

Whip and tongue graft, rind graft

Examples include: Betula, Carpinus, Cercis, Daphne, Fagus, Robinia,

Viburnum, Wisteria

Examples include: Reworking of failed

budded stocks, Prunus ‘Amanogawa’,

Robinia cultivars

Side grafting

Bench grafting Field grafting

Side veneer graft, modified side veneer graft

Chip budding, ‘T’ budding

Examples include: Acer palmatum cultivars,

Betula, Carpinus, Cercis, Daphne, Fagus, Magnolia,

Viburnum and various conifers

Examples include: Field-grown trees,

roses, some specialist shrubs

Field grafting

Figure7.SummaryofgraftingtechniquesSource:CourtesyofLeeWoodcock,PalmsteadNurseriesLtd

Bench graftingThewintermonthsofDecembertoMarchoffera good opportunity for bench grafting bare-root or container-grownrootstocks,whiledormantorinmidtolatesummer(JunetoAugust)oncontainer-grownrootstocks.Thetermbenchgraftingisliteral,astheoperation can be undertaken at a comfortable workingheight.Whip or splice graftThisisthemostsimpleofgrafts,withoneslanteduppercutontherootstockwithanequalmatchedcutonthescionforprecisecambiumcontact.Itisidealwhererootstock and scion are of similar gauge and forms

aneatcleanunion.Itisverysuitablewherethegrafterisalsotyingthegraftasthewholeoperationisdoneinthesamemovement.Thistechniqueissuitableforevergreen subjects such as Rhododendron.

Requisite cuts made to the scion (top) and rootstock (middle), withthetwocutsjoinedtogethertoformthegraft(bottom)

.Whiporsplicegraftingisidealwhererootstockandscionareofsimilar thickness, enabling a neat, clean union to be formed

Cleft or wedge graftThisisoneofthemoreversatilemethods,wherethe scion is usually much smaller than the rootstock andwhererootgraftingisalsopossiblesuchaswithWisteria and Gypsophila.Itisalsowidelyusedinlaboratorieswithsoftgrowthonsubjectssuchaspotatoesandtomatoes.Thescionispreparedasawedgewithequalcutsonbothsidesandtherootstockissplitdownthemiddle.Thescionisthenwedgedin tolineupwithatleastonesideofthecambiumof stockandscion.


Stagesinacleftgraftwherethescionmaterialismuch smaller than the rootstock

Side veneer graftThis is the most commonly used method for summer grafting and part or all of the rootstock is retained abovethescionaftergrafting.Adownwardcutis made on the side of the rootstock to remove a slice of rind,retainingatongueintowhichtheendofthescioniswedgedwhentippedoffontheoppositesidetothemaincut.Thewidthofthiscutcanbeestimatedtomatchthatofthescion.Thesideveneergraftisalsousedforwintergrafting.

Withthesideveneergraft,adownwardcutismadeontherootstock and a cut of similar length made on the scion such that the cambial layers match up

Modified side veneer graftThis method is very similar to the side veneer but the tongue remaining on the rootstock is extended up overthegraftasanadditionalflapbeforetyingin. The cambium layer is also exposed on the outer side ofthegraft.Thisintricategraftisgenerallyonlyused onparticularlydifficultsubjects,wheretheextracambiumcontactensuresagood‘take’.

Similar to the side veneer but the remaining tongue on the rootstock is extended over the graft

Adownwardcutismadeontherootstockandthetongueisretainedatthebaseofthecut,intowhichthescioniswedgedwhentippedoffontheoppositesidetothemaincut


.Rootstocktongueofmodifiedsideveneergraftreadyto receive scion

.Completedmodifiedsideveneergraftbeingtiedin

Field graftingThetwograftingmethodsdescribedherearespringmethodsusingdormantgraftwoodthathasgenerallybeencoldstored.Thewhipandtonguemethodisnotreliantonrisingsap,whichmeansitcanbeundertakenfromearlyMarchonwardsbuttherindgraftisonlysuccessfulwhenthebarkiseasilyseparatedatthecambiumlayer.Thismaybeaslateasearlytomid-April.Whip and tongue graftThegraftiscutasforawhipgraftandatongueiscutback in on the cut surface, replicating the same on the cutdownrootstock,sothatthetwotongueswedgetogether.Itisimportantthatthecutsurfaceofbothrootstockandscionarematched.Generally,withfieldgrafting, the rootstock is larger than the scion but, even so, a precise match can be made if the rootstock is only cutlightlytoexposeanarrowcambium.

Thewhipandtonguegraftingprocesswithcutstothescionandrootstock, and their joining together to form the graft

.Completedwhipandtonguegraftsecuredwithbiodegradablerubbertieanddippedinwax

Rind graftThe knife blade edge held at 90º is used to make a verticalcutalongthelengthoftherootstock.Thegraftitselfispreparedasforawhipgraft,withtheendofthe scion stubbed so that it can be pushed under the barkoftherootstock,intothecambiumlayer.Thebarkwillliftandseparatebutretainenoughpressuretoholdthegraftinplace.Tyingofthegraftisthesameasforawhipandtonguegraft.Thismethodisoftenusedfortop-workgraftinginorchardstochangevarieties.


Adownwardcutismadeontherootstockwiththeresultingflapbeing retained to extend over the inserted scion and completed graft prior to tying in

Field buddingThetwobuddingmethodsdescribedhererelyontherootstockbeingactiveingrowthatthesametimethatthebudwoodismature;thesetwoconditionsarekey toasuccessfulunionofrootstockandbud.Dependingonthesubject,thiscouldbeasearlyaslateJuneforroses (‘T’ budding) and as late as mid-September for somefruittreesandornamentals(chipbudding).Easyplantsubjectsaretolerantofawidewindowofopportunitywhilethemoredifficultsubjectsrequiremoreattentiontoprecisetiming.The rootstock is prepared in advance by trimming acleanstemabovetheground.Heightofbuddingvaries,withrosesitisatsoillevel,inthecaseofother ornamentals it is at a visually aesthetic height, approximately10cmaboveground.Fruittreesareusually budded at around 15 cm above ground to avoidthescionrootingatthetimeoffinalplanting.Budwoodshouldbekeptmoistandintheshadeat alltimeswhilebuddingtakesplace.Materialcanbekept under a moist cloth or sacking or held in a bucket withthebutt-endsinafewcentimetresofwater.Whether degradable materials such as rubber or non-degradable polythene tapes are used, the important timefornaturalorpredeterminedreleaseis4–6weeks.During higher than average ambient temperatures, in combinationwithgoodrootstockgrowingconditions,thecallusingwillbequicker.‘T’ buddingIt is only possible to undertake ‘T’ budding if the plantsapisrisingsothatthebarkliftseasilyawayfromtherootstock.Irrigationisausefulfacilitytohelppreparetherootstockconditiontocoincidewithbudwoodmaturity.

A short cut around 4 cm long is made along the length of rootstock stem, just deep enough to penetrate the bark and at the top of this another cut is made around 12mminlengthatrightanglestothefirst,ineffectformingthe‘T’fromwhichthetechniquetakesitsname.The bark on either side of the longer cut is then lifted backtoreceivethebud.

.The‘T’buddingprocess,withthebudwithinthe‘shield’,the‘T’cutontherootstock,insertedbudandcompletedbudwithtrimmed shield

Abudisthenselectedandcutfromthebudwood,startingaround1–2cmbelowthebud.Onremoval,thewoodatthebackofthebudisusuallyleftintactandthebud ‘shield’ inserted into the top of the ‘T’ cut, pushing downgentlytosecureitunderthebark.Anysurplus‘shield’ protruding from the cut should then be trimmed offwithasharpknife.Thebudsarethentiedinfirmlybutnottootightly,workingfromthebottomtothetopofthewound.The scion bud is left exposed or covered by the tie depending on its vulnerability to damage from pressure duringthecallusingperiod.Wherebudpatchesareused, as in the case of roses, these are stretched over the face of the ‘T’cut and bud, and held to the stem bystaples.The bud patch gradually degrades as callus develops andtheunionisformed.Budded rootstocks are headed back to just above the scionbudthefollowingwinter,usuallyinFebruaryorearlyMarch.


.

Bud selection for the budding process

.Sufficient‘shield’sizeonthebudwoodtopermiteasyhandling

.Bud insertion into the rootstock

.Bud patch

.Bud patch degradation

Making the required cuts in the ‘T’ budding process


.Final union in the budding process

Chip buddingDevelopedbyDrBrianHowardatNIABEMR,thisform of budding replicates single bud grafting as the cambiumlayersofrootstockandbudmatchprecisely.It is found to produce a more consistent ‘take’ for most subjectsandwillproduceamoreuniformstandoftreesinthemaidenyear.Inpractice,ithasalsoprovedtobe faster for the operator but the tying requires more precision,asthebudiseasilyshiftedoffline.A clean, smooth spot on the stem should be chosen for budding.Thefirstcutintothestemismadeataround20°toadepthofaround3mmtoformtheliponwhichthescionbudsits.Asecondcutismadeataround4cmabove this cut and an inverted U-shaped cut is then madebackdownthestemtothefirstcut.

.Thechipbuddingprocess,showingpreparationofthebud(top)androotstock(bottom)togetherwiththebudandrootstocktogether on completion

.Required cuts in the rootstock to receive the bud

Onthebudwood,thescionbudisremovedbymakingsimilarcutsandthenliftingitbetweenthumbandknifeblade.Itisthentransferredtotherootstockwherethecutlipshouldfirmlyholdthebud.Matchingupthecambium layers of both scion bud and rootstock is againtheprimeaim.

.Bud in position on the rootstock

The same methods and principles apply to tying chip budsasfor‘T’budding.Aschipbudsaremoreexposedthan a ‘T’ bud, tying accurately to secure the bud correctlyismorecritical.


.Tying in the chip bud needs to be an accurate procedure

Chipbuddingisnowtheacceptedtechniqueforornamentaldeciduoussubjectsaswellasfruittrees. Itcanalsobedoneusingcontainer-grownrootstocks.

.Chipbudonacontainer-grownrootstock

Propagation facilitiesWinter graftingBench grafting procedures are carried out during thewintermonthswithdormantmaterial.Itiscriticalthat the scion material of deciduous subjects is fullydormant.With bare-root grafting, the completed grafts can beplungedinamoistmediumandpottedupwhen the buds are bursting on the scion or dormant from coldstore.Whengraftingontocontainer-grownrootstocks,thesewillneedtobebroughtunderprotection,iftheyhave

beengrownoutside,andwellbeforegraftingtakesplaceOctoberisnottooearly.Thisisbecausethemedium in the pot needs to be dried out to a just moistconditionpriortografting.Deciduousmaterialcanbedippedinmoltenwax andstoodonopenbenchesorbedsonthefloor oftheprotectedstructure.Conifersandevergreenswillneedtobeplacedinapolythenetentwherehighhumiditycanbemaintained(ascandeciduousmaterialifnotwaxed).Baseheating,whetherinbedsonthefloororraisedbenching, is most important, as activity in the rootstock needstoprecedethatofthescion.Therefore,airtemperaturesneedtobecool.Basetemperaturesof18–20°Carehighenough.Otherthaninsevereweather,base heating usually ensures frost-free conditions, even inpolythenetunnels.Air heating facilities should be considered to augment the base heating during very cold periods, especially iftheseoccurinFebruaryandMarchwhengraftscouldbemakinggrowth.Theprovisionofheatwillspeedupthe uniting of rootstock and scion so protected facilities forgrowingthegraftsonwillberequired.Whenusingfacilitieswithnoformofheating,itisimportant for the uniting of rootstock and scion to beaslowprocess.Budburstandcommencement ofgrowthshouldonlybetwotothreeweeksearlier thantheplantsnaturalbudburstoutdoors.It is, therefore, important on sunny days to vent the glasshouse or polythene tunnel to prevent air temperatures getting much higher than the outsidetemperature.Thereisalwaysariskofprolongedfreezingperiodscausing damage to the grafts and it is here that portable heaterswouldberequired.Summer graftingSome subjects such as Acer palmatum, Hamamelis and Magnolia are suited to this system and are heavily reliantonthesideveneermethod.Bynecessity,container-grownrootstocksareused,whichdonotneedtobebroughtinsidepriortografting.Theyshouldbekeptmoistatalltimesandnotallowedtodryout.Leaves are retained on the scion or can be reduced in sizeiflarge.Itisimportanttousewell-ripenedscionwood.Notimeshouldbelostingettingcompletedgraftstothepropagationfacility.Normally,lowpolythenetentsareusedbutfoggingunitsareanalternative.Weanedandestablishedgraftscanbegrowninoutdoorframes,coldglasshousesorpolythenetunnelsfortherestofthesummerperiod.Use of cold storesCold stores can be used to extend the grafting or buddingseasonbykeepingscionwood,budwood androotstocksdormant,ifthisisrequired.Theyare also useful for short term storage of summer scion


woodandbudwood,helpingtoremove‘fieldheat’andkeepmaterialfresh.Directcoldairflowsystemsgenerallydehumidifytheairsoplantmaterialwilleitherneed to be sealed in plastic or held on shelves and the floorofthestorewateredregularly.Ajacketedcold storewithindirectcoolingispreferable.

Hot-pipe callusingThis technique is particularly useful for subjects prone tofailureatthecriticalpointwherecallusformationisnotadequatetosupporttheearlygrowthstageofthescion.Thisdifficulttransitionalperiodisassistedbypre-callusingthegraftunionwhiletherootstockandscion remain dormant, thereby reducing losses at the weaningstage.Italsoallowsawideruseofbare-rootrootstocksinplaceofcontainer-grownones,reducingcostsconsiderably.Itisalsoparticularlysuitableforallapicalgraftingandallowsthissimplergrafttoreplacesideveneerinsomesituations.SubjectsparticularlysuitableforthismethodareshowninTable10.Mostspecieswithinthesegeneraapply.Inprinciple, any grafting subject can be ‘hot-piped’ if the temperatureanddurationisknown,however,theextracostoftheoperationisnotjustifiedformanyoftheeasiertopropagatesubjects.Hot-pipe constructionSeveralheatsourcesareequallyaseffective,includingelectricsoilwarming,selfregulatingcablesandhotwatersystems.Theimportantdesignfeatureistobeabletofocusheatoverthegraftunionaccuratelywithoutanyfluctuationofmorethan1–2°Ceitherwayandtokeeptheouterperimetersofscionandrootstockcool.

Table10.Optimumtimesandtemperaturesforarangeofsubjectswhenhot-pipecallusing

Subject Max time (days)

Temperaure (ºC)

Callus formation

Aesculus 18 22 Average

Amelanchier 18 20 High

Betula 18 22 Average

Carpinus 16 22 High

Castanea 18 22 High

Corylus 14 20 High

Fagus 18 20 Average

Gleditsia 18 20 Average

Ginkgo 18 22 Average

Liriodendron 16 24 High

Morus 18 20 High

Juglans 18 18 Low

Quercus 16 22 Average

.Bare-root grafts ready for hot-pipe callusing

.Bare-root grafts being laid out for hot-pipe callusing on an electric self-regulating pallet system

Graftsinpositionforhot-pipecallusing;therootsarecoveredwithpeattoconservemoistureandthegraftunionpositionedtoreceive heat


Heatmustbewellcontrolledandfocusedaroundthegraftunions,enabling the rest of the scion and rootstock to remain cool

The key principles of hot-pipe callusing are:

• Roots must be kept moist at all times

• It is important not to exceed the recommended temperatures or times

• It is advisable to maintain a slight air gap betweenheatsourceandgrafttoavoidhotspots

• Even small amounts of callus are advantageous to graft survival

• Some sucker development around the union is acceptable

• Cold storage of callused grafts after removal from the bed is acceptable

• Plantmaterialshouldhardenoffover2–3days after the times stated in Table 10

AftercareThis is as important as the grafting and budding processestoavoidunnecessaryplantlosses.Bench grafted materialThemostimportantfactorwithcontainer-growngraftsisregulatingmoisturecontentatthe‘justmoist’level;ifallowedtogetwet,eitherbyoverwateringorfromcondensationdrips,failurewilloccur.Ifallowedtogettoodry,lossescanalsooccur.Bare-rootgraftscanalsobelostwhenpottedupifwateredtoomuchbeforetheymakenewroot.Wateringshouldonlybeincreasedwhenthegraftsstartmakingreasonablegrowth.Timely removal of suckers is important so they don’t competewithsciongrowth,althoughsomesuckergrowthmayhelptoavoidoverwinteringproblems. Earlycaningandtyinginofnewgrowthiscrucial and the need for prompt pest and particularly disease controlisessential.Field grafted materialNon-degradabletiessuchaspolythenegraftingtapeshouldberemovedonceawell-establishedgraftunion

has formed and before any constriction takes place due toexpansionoftherootstock.Thisisalsonecessarytoavoid fungal infections that may develop beneath the tiesiftheyremaininplacetoolong.Shootsshouldgrowawaystronglyoncetheunionhasformed.Anydoubleleadingshootsshouldbecutbackby about half, leaving the strongest and straightest intacttogrowon.Anylateralshootsshouldalsobe pruned back and rootstock suckers rubbed out whiletheyarestillsoft.Pestsanddiseasesshouldbecontrolledpromptlyandtheareakeptfreeofweeds.During the maiden year, any further rootstock suckers should be removed promptly and those subjects requiring support caned and tied, placing the cane at thebackofthegraftunion.Atop-dressingoffertilisershould be applied in the spring or summer if required, inaccordancewithsoilanalyses.Goodlevelsofweedcontrolshouldbemaintainedtominimisecompetition.Field budded materialNon-degradabletiesshouldberemovedpromptlyonceawell-establishedbudunionhasformed.Pests,diseasesandweedsshouldalsobekeptunder closecontrol.The rootstock tops should be removed (‘headed back’) tojustabovethescionbudduringthelatewinterperiodtoenablemaidengrowthtodevelopunhindered.Goodweedcontrolshouldbemaintainedthroughoutthe maiden year and a top-dressing of fertiliser applied duringthespringorsummerperiodinaccordancewithsoilanalyses.Subjects requiring support should be caned and tied promptly,placingthecaneatthebackofthebudunion.With chip budded material, bud guides can also be used to direct and protect the leading shoot as it emerges from the bud, helping to avoid the characteristic ‘dogleg’thatmayotherwisedevelopatthisstage.

DivisionMany herbaceous perennials, alpine plants and ornamental grasses can be propagated quickly, reliably and economically by the division or splitting ofcrowns.Whilefairlystraightforwardtodo,divisiondoesrequiresignificantquantitiesofstock.Itisalsolabourintensiveworkanditsusehasdeclinedinfavourof other methods, notably seed or cutting raised plug plants and, to a lesser degree, the use ofmicropropagatedmaterial.Herbaceous perennials that can be propagated by division include Aster, Astilbe, Bergenia, Doronicum, Epimedium, Geranium, Hemerocallis, Helenium, Hosta, Iris, Rudbeckia and Stachys.Manymat-formingandground cover alpines can also be increased by smallermini-divisions,usuallyinspringwhenthe plantsareactivelygrowing,includingChiastophyllum, Gentiana sino-ornata, Geranium, Lysimachia, Polygonum and Raoulia.Variousmossyandrosette


forming Saxifrage species, Sedum, Sempervivum andThymuscanalsobepropagatedinasimilarway,althoughineffectthesearemorelikerootedcuttingsthantruedivisions,duetothenatureoftheplants.Divisionisalsoausefulandspeedywayofpropagatingclump forming bamboos and ornamental grasses such Carex, Festuca, Miscanthus, Phyllostachys, Sasa and Stipa.Although division is done primarily during the quieter autumnandwintermonthswhenthecrownsaredormant,somecropsrespondwelltosummerpropagationafterflowering,notablyDoronicum, Epimedium, Hemerocallis and Iris.DivisionsofIris, typically,compriseasmallportionofrhizomewithroots attached and a ‘fan’ of leaves that are trimmed to abouthalftheirsize.WithEpimedium, young rhizomes producedafterfloweringarecutupintosmallerpieces,eachwithrootsattachedandeitherlinedoutorpottedupforgrowingon.Dormantcrownsaresplitintoasmanypiecesaspossible, using the younger, more productive outer portionsratherthantheoldercentralcore.Eachdivisionshould have roots and dormant buds attached although some subjects (such as Hosta) usually comprise single buddivisionswhileothers(likeAster and Stachys lanata)aremorelikerootedcuttings.Similarly,thethickfleshyrhizomesofBergenia can be cut up into small sections, typically 3–4 cm in size,eachwithadormantbudattached.Duetotheirsmall size, they are usually inserted horizontally (bud uppermost) into seed or plug trays or small pots and propagatedonaheatedbenchorbed(at18–21°C),under clear polythene covers initially, until the buds areforcedintogrowth.Oncenewrootshavedeveloped, the young plants are potted and grownonunderprotectionuntilwellestablished.During splitting, any dead or decaying foliage is removed.Ornamentalgrasseswithlongfoliagesuch

as Carex, are usually trimmed to reduce the leaves to about half their length to enable easier handling and encouragevigorous,compactgrowthinspring.Followingdivision,theyoung‘splits’areusuallypottedforgrowingonthefollowingspringorlinedoutinthefield.Coldstoragecanbeusedtoholdstockback until planting conditions are suitable or bed space isavailableforpotting.

LayeringLayeringinvolvesrootingshootswhiletheyarestillattachedtotheparentplant.Thereareseveralwaysofdoingthis.Simplelayeringinvolvespeggingdownshoots produced the previous year, usually at their tips.Frenchlayeringinvolvesthepeggingdownofshootsalongtheirentirelength,suchthatnew,uprightshoots develop along the complete length of stem and serpentine layering is an adaption for species producing longannualshoots.It is one of the oldest propagation techniques and, untiltheendoftheeighteenthcentury,wasthechiefmethodused.However,itscommercialimportancedeclined as the rooting of stem cuttings became better understood, aided by the advent of mist propagation duringthe1950s.Itslabourintensivenatureandattendantdifficultieswithweedcontrolalsocontributedtoitsdecline.However,itisareliabletechniqueforthepropagationofHNSsubjectsthataredifficultorveryslowtorootfromcuttings,particularlythoserequiredforsaleontheirownroots.Largesaleableplantscanbeproduced quite quickly, such plants are normally rooted inthefirstyearandgrownonforsaleduringthesecond.Simple layeringThisisusuallycarriedoutduringMarchtoJunewhenshootsareinactivegrowth.Strong,youngshootsproduced the previous year are arched over and pegged downaroundthestockplantsothattheyrootintothe

Irisrespondswelltosummerpropagationandisoneofmanyherbaceoussubjectsthatcanbeincreasedreadilybydivision


surroundingsoil.Whilethesearerootingduringthesummer,newshootsemergethatarepeggeddownthefollowingyear,tocontinuethecycleandprovide asuccessionofshoots.Normally,rootedlayerscanbeliftedfromautumnonwards,linedoutorpottedforgrowingon.Mostsubjectswillbewellrootedwithinonegrowingseason,althoughslowerspecieslikeMagnolia and Rhododendronwillrequireleavingdownforlonger,usuallyaround18months.For all layering techniques, adequate irrigation during dryperiodsisessential,asispromptcontrolofweedproblemsandgoodnutrition.HNSsubjectssuitableforsimplelayeringinclude:Celatrus, Chimonanthus(inJulyandAugust), Cornus controversa, Corylus avellana, Corylus avellana ‘Contorta’, Corylus maxima ‘Purpurea’, Corylopsis, Cercidiphyllum japonicum, Hamamelis, Fothergilla (in August), Parrotia persica, Stachyurus praecox, Syringa microphylla ‘Superba’, Syringa vulgaris cultivars, Tilia cordata, Tilia x euchlora, Tilia x europaea, Viburnum plicatum cultivars, Viburnum tomentosum and Wisteria.DeciduousAzalea can also be layered if softcuttingsprovedifficultandwhilemanyspeciesandcultivars of Rhododendronarenowraisedfromcuttings,simplelayeringisausefulalternative.French layeringThis technique yields considerably more plants from a single shoot and in turn each stock plant, than simple layeringinwhicheachstemproducesjusttheoneplant.Theannualmanagementprogrammediffersinthatthepeggingdownhorizontally(asdistinctfromarchedinthe case of simple layering) of shoots for their entire lengthisusuallydoneduringJanuaryorFebruary.Duringthespring,thenewshootsformedfrombudsthat have broken along the length of stem, are gently coveredwithsoilwhenaround5cminheight,suchthatonlythetipsarevisibleabovesoillevel.Ineffect,theyare ‘earthed up’ and the process is repeated once or twicemorewhentheshootshavemadefurthergrowthtoensurethehorizontalshootsarecoveredwith around15cmofsoil.Usually,thisworkiscompletedby early summer and the plant material is lifted from autumnonwards.HNSsubjectssuitableforFrenchlayeringincludeAcer cappodocicum ‘Rubrum’, Acer saccharinum ‘Laciniatum’, Alnus cordata, Alnus incana, Carpinus betulus ‘Fastigiata’, Chiminanthus praecox, Chiminanthus praecox ‘Lutea’, Corylus colurna, Corylus avellana ‘Aurea’, Corylopsis pauciflora, Cotinus coggygria and cultivars, Euonymus europaeus ‘Red Cascade’, Hydrangea paniculata, Hydrangea quercifolia, Styrax japonica, Tilia platyphyllos ‘Rubra’, Viburnum bodnantense and Viburnum farreri.Serpentine layeringThis technique is adapted to species producing long annual stems such as Clematis and Wisteria.Thestemsarebroughtdowntogroundlevelandburiedatintervals

along the stem in a snake like fashion, leaving at least onebudoneachabovegroundportionofstem.Newshootsgrowfromthebudsandrootsfromwithintheburiedarea,atwhichpointthestemsaresectionedandyoungplantsliftedwhenestablishedtobegrownon.

Stooling (mound layering)This is the simplest form of layering, relying as it does on the principle that if a young stem is placed in darknessitwillproduceadventitiousroots.Itisalsoarelativelyefficientmethodofpropagation,enablingtheproductionofalargenumberofwell-rootedplantsperunitarea.However,itisonlysuitableforvigorous,usuallydeciduoussubjectsabletowithstandandreplace annually the removal of all shoots during the dormantperiodbyquiteseverepruning.

Stool beds remain the principal propagation method for raising apple rootstocks

Once established, shoots produced by the stool bed are earthed-up in spring to blanch them and so induce rootinitiation.Thisprocessisrepeatedtwicemoreas


theshootsgrowduringthesummer.Therootedstemsarethenprunedawayinmid-winterfromtheparentplantfortransplantingandgrowingon.Typically, the economic life of a stool bed varies from around12to20yearsdependingonspeciesandhowwellitismanaged.Usually,theyarefullyproductivewithinthreetofouryearsafterplanting.Although largely superseded by advances in the rooting of stem cuttings, stooling is an alternative and reliable, if labour intensive propagation method, for a range of HNSsubjectsincludingcultivarsofAcer cappadocicum, Acer saccharinum and Acer palmatum, various ‘snakebark’ maples, Berberis species (notably, Berberis dictophylla and Berberis temolaica), Cercis, Chaenomeles, Chimonanthus, Cornus, Corylopsis spicata, Cotinus, Halesia, Hoheria, Hydrangea paniculata, Morus, Prunus glandulosa, Prunus tenella and Prunus cerasifera cultivars, Ulmus, Viburnum bodnantense and Viburnum farrerii.

Youngshootsareearthedupregularlywheninactivegrowthtopromoterootingandthenprunedawayinmid-winterforgrowingon


Influence of water, temperature and lightThe essential environmental requirements for propagation via cuttings include: a humidity level sufficienttoreducewaterlossfromleaves,anappropriatetemperatureregime(thiswillvarywithspecies)andadequatenaturallight.Thesecanbeprovidedbysimple,close-contactpropagationfilm laid directly over cuttings, polythene tent or ‘cloche’ systemsorvariousmistorfogsystems.Thelatterproviding the high humidity supportive environment neededtorootverysoftmaterial.WaterWhen cuttings are removed from the parent plant, their naturalwatersupplytotheleaffromtherootsceases,yetwaterlossbytranspirationcontinues.Thisresultsinwaterstressthatcanpreventrootingandpromoterotting.ManyeasyrootingHNSsubjectsavoidseriouswaterstressbyclosingstomataquicklyandcontinuingtotakeupwaterthroughthecutbase.Moredifficultrootingspeciesarelessabletoavoidwaterstressandso require a more supportive environment until adequate newrootshaveformed.Similarremarksapplytosoftcuttingmaterialpronetorapidwaterloss.Toreducetranspirationandwaterlosstoaminimum,thevapourpressureofthewaterintheatmospheresurrounding the leaves of the cuttings should be maintained to a point that is almost equal to the vapourpressureintheintercellularspaceswithin theleaf.Todothis,ahighrelativehumidityisrequired,combinedwithleafwettingtohelppreventleavesbecomingwarmerthantheairaroundthem(the internalwatervapourpressureincreasesrapidly withtemperature).The development of mist propagation during the 1950s wasamajoradvanceinimprovingtherootingofsoft,leafy cuttings, relying as it does on the evaporative coolingeffectofmoistureonaleafsurface.Thiscoolingeffectreducestheinternalwatervapourpressureintheleafand,inturn,therateoftranspiration.Maintainingafilmofmoistureovertheleafsurfacealsocreatesthe requisite high relative humidity around the leaf and lowerstheairandleaftemperature,eachofwhichalsocontributetoreducingtranspirationrates.Underwell-controlledmistorfog,environmentalconditionsareusuallyidealforrootingleafycuttings.Transpirationandsowaterlossfromcuttingsis reducedtoalowlevelwhilenaturallightintensity canbehigh,sopromotingfullphotosyntheticactivity.Asthetemperatureofthecuttingisrelativelylow, the rate of respiration is reduced and so, in turn, the useofvaluablefoodreserves,whichareimportant forrootinitiationanddevelopment.Mist has enabled soft leafy cuttings to be propagated early in the season at a stage most favourable for rooting.Withoutmistorfog,suchmaterialwouldbedifficulttokeepturgidandroot.Thecapabilityofthetwosystemstoreducewaterlossalsoenableslargercuttingstobeusedwithgreaterleafareas.Thisoften

leads to improved survival, a greater number of healthy, vigorous roots and a larger liner in a shorter space oftime.Mist and fog systems require careful management tobeeffective.Shadeandsomeventilationwillbe required during hot spells in spring and summer, whiletheapplicationofwatermustbewellcontrolled toavoiddryingoutor,moreusually,overlywetconditionsprevailing.Excessivewaterapplicationalsoreducesthetemperatureofthepropagationmedium,whichmayinturnreducerooting.Italsoleachesandsodepletescuttings of valuable nutrient reserves necessary for optimumrooting.Diseaserisk(notablyfrom Botrytis, Pythium or Phytophthora) is also greater, underlining theneedforefficientcontrolofwaterapplicationtopreventdiseaseestablishmentandspread.TemperatureMostHNSsubjectswillrootwellwithquitemodestairtemperaturessolongasthereissufficientbaseheatprovided at the point of root initiation (although many specieswillrootequallywellcoldwithoutsuchheat).In terms of day and night-time air temperatures, 15–18°Cand12–15°C,respectively,willsufficeformostsituations,whilebasetemperatureswillvaryconsiderably, from zero (cold) for easy rooting subjects to21°Cforslowermoredifficulttorootspecies,atleastfortheinitialfewweeksfollowinginsertion.Asageneralguide,forcuttingsrequiringbaseheat,18–21°Cisusuallyadequate.LightAs light is the energy source for photosynthesis, its presence is of major importance in all types of plant growth,includingrootinitiationandgrowth.Withleafycuttings,lightintensityanddurationmustbesufficientto enable carbohydrates to accumulate in excess of thoseexpendedduringrespiration.Inleaflesshardwoodcuttings,suchdependenceisdrawnfromfoodreserveswithinthecutting.Generally,themorelightacuttingreceiveswithin certain limits, the more likely it is to develop a strong rootsystem,butitsabilitytobenefitfromhighlightdependsonhowwellthepropagationenvironment limitswaterlossandavoidsexcessivelyhightemperatures.Hightemperaturesincreaserespirationandsodepletecarbohydrate.Italsobecomesmoredifficulttorestrictwaterlossastemperaturesincrease.Excessiveshadingalsowilllimitphotosynthesis,soreducing carbohydrates necessary for root formation and development but, as a guide, 20% shade is considered optimalduringthespringandsummerperiod.Theabsenceoflightonstemtissueintheregionwhereroots are expected to form is of course conducive torootinginmanyHNSspeciesandisexploitedforcommercial purposes through the process of layering and the etiolation of stem cuttings to enhance rooting, forexample,withcultivarsofSyringa.

Propagation environments and systems

76 Propagation environments and systems

Insomesubjects,thelightinglevelunderwhichstockplantsaregrownmayinfluencetherootingandsubsequentgrowthofcuttingstheyproduce.Certainspeciesceaseactivegrowthinresponsetoanaturalreductioninlightintensityanddaylength.Forexample,withspringrootedcuttingsofdeciduous Azalea and dwarf Rhododendron potted on during late summer or earlyautumn.Thegrowthofsuchplantsimprovesconsiderablyifplaced under continuous supplementary lighting under glassinwintercomparedtoplantsgrowninnormalshortwinterdays,whichusuallyremaindormantuntilthefollowingspring.

Understanding the environmental needs of cuttingsAHDBHorticultureprojectHNS9:Understanding the environmental needs of leafy cuttings during rooting, considered the environmental needs of cuttings more closely and sought to assess the variability of propagation environments for leafy summer cuttings onacross-sectionofcommercialHNSnurseries,usingpolytheneorautomatedmistorfogsystems.Fromthework,itwasclearthat:

• Conditions varied greatly in many respects crucial to rooting and survival and that a high proportion of cuttingswereexperiencingsuboptimalconditionsduring propagation

• Therewasaworryinglackofawarenessamongnurserymenofwhatconstitutesagoodenvironmentforpropagatingleafycuttings,aviewsupportedbythe variable conditions observed on the nurseries as part of the study

• Thereweresignificantdifferencesinlightintensity,relativehumidityandleafwettingbetweennurseriesand,moreworryingly,withinpropagationareasonthesamenursery.Thesewereoftentheresultofdeficienciesincontrolequipment,lowwaterpressure, partially blocked nozzles and inadequate closure of the environment

• Nurserymenstillreliedheavilyonexperience rather than technology for control of the propagationenvironment,muchofwhichwasneededtocounteractmechanicaldeficiencies.However,thisoftenfailedtohavethedesired effect.Forexample,manualopeningofventsfrequently reduced relative humidity more than it did high temperatures, as intended

AHDBHorticultureprojectHNS76:Examination of techniques to raise humidity in mist houses, investigatedwaysinwhichpropagatorscouldachievethe environmental conditions needed for the cuttings of stress sensitive species to root successfully, for example, softwoodcuttingsof Cornus, Cotinus and Garrya.Such cuttings require a combination of generous leaf wettingandanatmospherethatisalmostsaturatedwithwatervapour(closeto100%relativehumidity).

Thiscanbeachievedwithagoodfogsystem,althoughmist is still preferred by many propagators because ofitsreliabilityandsuitabilityforrootingawiderangeofHNSsubjectssuccessfully.Earlyproblemswithfogincludedatendencyforoverwettinganddifficultieswithtemperaturecontrol,particularlyinnon-ventedsystems.Polythene enclosed mist systems (so called closed mist systems) can achieve comparable results to fog but sufferfromexcessivelyhightemperaturesunlesswellshadedandcarefullymanaged.Cuttingsarealsolessvisibleandsomoredifficulttomanage.However,theyofferacheaperalternativetofogandamoreconstantlevel of humidity compared to the more cyclic patterns ofleafwettingassociatedwithopenmist.Theyare,therefore,lessinclinedtobecomeoverlywet.Closedmistsystemsarealsoflexible,inthattheycanbereadilyadaptedforautumnandwinterpropagationbyreducingorsimplyswitchingoffthemistforsubjectspreferring a drier regime, for example, in the case of manyconifersandevergreenspecies.InHNS76,rootingtrialswithleafycuttingsofarangeofHNSspeciesinalarge-scaleclosedmistsystemwerecomparedwithahighlysuccessfulventilatedfogsystemandaconventionalopenmistsystem,followinginitial studies examining the factors determining the temperatureandhumidityachievedinawell-sealedpolytheneenclosure.ArangeofHNSsubjectswereincludedinthestudyincluding: Acer platanoides‘CrimsonKing’,Acer platanoides ‘Drummondii’, Cornus alba ‘Elegantissima’, Corylus maxima ‘Purpurea’, Cotinus coggygria ‘Royal Purple’, Garrya elliptica‘JamesRoof’andMagnolia soulangeana.Apicalcuttingswerepredominantlyused,treatedwithanIBA‘quickdip’andstruckduringJulyandearlyAugust.Forthemainsubjects,assessmentsforrooting,basaldecayandroot-ballvolumeweremadeat28and55-dayintervals.Theconclusionsfromtheprojectarepresentedbelow:

• Closedmistsystemscanbescaledupsufficiently to make them attractive to propagators, increasing themtoalarge,walk-inenclosureenablingeasier,regularinspectionsofcuttings,withseveralmist lines rather than one

• The humidity level achievable in a large-scale closedmistsystemwascomparabletothatof a good fog system

• The high humidity in a closed mist environment became localised to the misted area, if only part of theenclosurewasmisted.Ifthemistintervalwas toolongthenhumiditydroppedbetweenbursts

• ForthemostsensitiveHNSsubjects,fogwasmoresupportivethanclosedmist; Garrya elliptica‘JamesRoof’,forexample,rooted100%infourweeksinfogcomparedto67%aftereightweeksinclosedmist

Propagation environments and systems 77

• Theadditionofsmallquantitiesoffinedropletfog,such as can be produced ultrasonically, to raise the humidity of incoming air in ventilated mist environments enabled additional support, such that theadvantagesoffog(humidificationofincomingair)andmist(uniformleafwetting)werecombinedforbesteffect.Asultrasonicfoggershavealowoutput,mistwillprovidethemainsupportduring stressful conditions

• Initial tests indicated that such a system enabled limitedventilationofclosedmistwithouttherelativehumidityfallingsubstantiallybelow100%

• Under bed insulation (to reduce energy loss) tended to increase temperature lift in closed mist systems by reducingheatlossintotheground.Thedegreetowhichthisoccurreddependedontheheatstoragecapacity of the material above the insulation layer

• Floorsorbencheswithcapillarymatting offeredminimalthermalbuffering,leadingto larger temperature variations

• Heat loss by radiation is unlikely to account for much of the heat loss from closed mist systems, as both waterandUVstabilisedpolytheneabsorbradiationquitestronglyintheinfraredwaveband

Recommendations from the projectTo create a more supportive environment in large-scale closed mist systems:

• Ensuretheenclosureisrobustandwellsealed as even a small opening can dramatically reduce humidity

• Ensuretheentirefloorarea,includingaccesspaths,iskeptwetbyperiodicdampingdown

• Beawarethatheavycondensationonthepolytheneprovides no guarantee that humidity is high around the cuttings

• Useexternalreflectiveshadingtominimiseheatload;thisisessentialandmoreeffectiveifsupportedawayfromthepolytheneoftheenclosure

• Usefloorlevelbedsratherthanbenchesorbedswithunderbedinsulation,asthesearelesslikely to lead to higher daytime temperatures

• Use at least 5 cm of sand beneath the propagation traystohelpensurethattherootingmediumiswelldrained, even during frequent misting, and to limit maximum temperatures, even if under bed insulation is used

Thisworkshowedthatfogprovidedaslightlymorefavourable environment than enclosed mist (particularly with Garrya cuttings) despite there being no detectable differenceinhumidityandcuttingsappearingwellwettedthroughout,inbothsystems.Themoresupportive environment of fog is thought to be due to the more constant humidity it provides around the cuttings.

Water loss from leaves depends on the conditions immediatelyoutsidetheirstomata,whichinmostHNSspecies are concentrated on the underside of the leaves.Astheleavesabsorbradiation,theytendtowarmupandthiswarmthisthentransferredtothe airpassingclosetothem.Thus,eveniftheairissaturated, the relative humidity drops and the vapour pressuredeficitincreasesnexttotheleaves.However, iftherearedropletsofliquidwatersuspendedin theair,astherearewithfog,thenthosedropletswill tend to evaporate and so maintain a relative humidity closeto100%.Althoughthewiderconclusionfromthisworkwasthatconsiderable improvements over conventional ‘open’ mistarepossiblewithouttheneedtodeployfog,amodest input of (ultrasonic) fog to complement mist mayyieldgreaterimprovements,atleastwithsomesubjectspropagatedbyleafycuttings.NotallHNSsubjectsrequireorevenbenefitfromamoresupportiveenvironment;itismainlythoseconsidereddifficulttorootthatarelikelytorespondsignificantly.

Light levels and shadingLight levels are the single most important factor regulatingtherateofwaterlossfromcuttings.Whilelight is essential for photosynthesis and developing adequate carbohydrate reserves needed for root growth,toomuchlightresultsindryingoutand poorrooting.There is also some evidence to suggest that high light canhaveaninhibitoryeffectonrooting.Forexample, at the former Glasshouse Crop Research Institute (GCRI)inSussex,whenViburnum x bodnantense ‘Dawn’waspropagatedundermistusingvaryingdegrees of shading, best rooting occurred at the lowestlightlevelwithprogressivelypoorerrooting asthelightincreased.Subsequentleaftissuemeasurementsshowednoappreciabledifferences inturgor,suggestingthatlightalonewasinsome wayinhibitingrooting,aconclusionalsodrawn fromotherresearchwork.During propagation, a balance needs to be struck betweenkeepingcuttingsturgidandallowingsufficientphotosynthesis to produce adequate carbohydrates forrootformationandgrowth.Duringthespringandsummer period, this is usually achieved by mist or fog butworkbyDrKeithLoachatGCRIshowedthat,byusing shading to control light levels, it is possible to achieve good rooting using cheaper systems, namely contactpolythene(althoughthisworkcanalsobeextrapolatedtopolythenetents).ThisworkestablishedappropriatelightlevelsforsuccessfulHNSpropagationunderpolythene;rootingdeclinesrapidlywhendailyradiationfallsbelow1.5megajoules(MJ)/m2 and optimally should be about twicethisvalue,3MJ/m2 (typically, the daily radiation intheUKrangesfromaround2MJ/m2inmid-winter to20MJ/m2inmidsummer).


Shading regimes need to take account of the naturally widevariationsindaylightthatoccurindifferentmonthsoftheyear,timeofdayanddifferentweatherconditions.Automaticshadescreensthatcanbedrawnoverpropagation beds at a preset light level provide the requisiteflexibilitytorespondtovariationsandadjusttheshadelevelsaccordinglybut,insituationswhereshading regimes are run manually, a subjective decision hastobereachedwhetheritisa‘dull’or‘bright’dayandashadelevelselectedaccordingly.This,ofcourse,maychangeduringthecourseoftheday.DuringtheGCRIwork,ashadingschedule(Table11below)wasdevisedtoguidegrowersonappropriateshadelevelsinpropagationareasfordifferentmonths oftheyearandweatherconditions.While very much an approximation, it provides a useful pointofreference,particularlywhenpropagatingunderpolythene,wheretemperaturescanbuilduprapidlybeneaththecover.Cuttingsundermistwilltolerateawiderrangeoflightlevels,buttheinformationprovidedcanstillbeusedforguidance. GoodrootingofmanyHNSsubjectscanbeachievedunder

polythene systems using shading to help control light levels

Table11.Shadingschemeforpropagationofwoodyornamentalsunderpolythene

Month

Number of layers* of 40% shade cloth** required

Sussex Day type***

Southport Day type***

Stirling Day type***

Bright Dull Bright Dull Bright Dull

January 0 0 0 0 0 0

February 1 0 0 0 0 0

March 2 0 2 0 1 0

April 3 1 3 1 2 0

May 3 1 3 1 3 1

June 3 1 3 1 3 1

July 3 1 3 1 3 1

August 3 1 3 1 3 0

September 2 0 2 0 2 0

October 1 0 1 0 1 0

November 0 0 0 0 0 0

December 0 0 0 0 0 0

* Ifglasshouseiswhitewashed(ApriltoAugust)useonelesslayerthaninthetable.** 1,2and3layersof40%shadeclothcutout(theoretically)40,64and78%,respectively,ofincidentlight.Checksshowedreasonable

agreementwiththesefigures.*** A subjective judgement of the day type is made each morning and the appropriate shade cloth is used, supported above polythene

coveringthecuttings.Note:Shadelevelsarecalculatedtogiveanaveragedailyradiationofaround3MJ/m2.


Thisschemedidnotallowfortimeofdayvariations.AtGCRI,twodifferentlevelsofshadewereusedthroughtheday;alightshadeforearlymorning(8.00–10.00am)andevening(3.00–6.00pm)andaheaviershadeforthemiddlepartoftheday(10.00am–3.00pm),depending onthemonth.The results of summer propagations (usually, the most challenging period for rooting cuttings under polythene)aredetailedinTable12.Clear,lightgaugepolythenewaslaiddirectlyoverthetopofthecuttingsandtheshadeclothsupported50cmaboveit.Alightlevelaveragingaround3MJ/m2wasachievedusing appropriate shade levels based on a subjective judgementofdullandbrightdays.Withthreesubjects(Cornus, Corylus and Philadelphus),betterresultswereachievedunderpolythenethanundermist.Subsequentworkalsoconfirmedthatproperlyshadedpolythenegives equally good and often better results than conventionalmistwithpotentialforsubstantial energysavings.Oncerooted,acuttingwillrequirehigherlightlevelsforoptimalgrowthandshould,therefore,beremoved(gradually)fromtheshadedregime.Table12.Comparisonofpercentagerootingofsummercuttingsunder mist and shaded polythene

Month and plant species Percentage rooting

June/July Mist Polythene

Forsythia intermedia‘Lynwood’ 96 100

Philadelphus ‘Burfordensis’ 59 95

Potentilla fruticosa ‘Red Ace’ 100 100

Weigela florida ‘Variegata’ 100 100

July/August Mist Polythene

Callicarpa bodinieri 97 95

Cornus alba ‘Sibirica’ 47 73

Corylus maxima ‘Purpurea’ 10 25

Hydrangea ‘Altona’ 95 98

Interaction of light and moistureLightandmoisturearethetwoenvironmentalfactorsrequiringmostattentionwhenseekingtooptimisetherootingofleafysummercuttings;theyinteractstronglybecauselight,whileessentialforphotosynthesis,stimulateswaterlossandsoincreasestheriskthatcuttingsbecomewaterstressed.AHDBHorticultureprojectHNS55:Strategies for liner production designed to achieve high-quality container plants,highlightedbigdifferencesinenvironmentalresponsebetweenspecies,especiallytowater.Cryptomeria japonica ‘Elegans Compacta’, for example,onlyrootedwhentherewaslittleornowetting,

whileGarrya elliptica‘JamesRoof’requiredveryheavywettingtorootwellandCotinus coggygria ‘Royal Purple’rootedbestwhenheavilywettedwithhighlight(buttoleratedlessmoistureatlowerlightlevels).Inthiswork,mostsubjectsfailedtorootifthelightlevelwasverylow.OnthenextpageTable13summarisestheenvironmentalrequirementsidentifiedduringthework.Severalotherconclusionswerealsodrawnfrom thiswork:

• Most cuttings fail if the light level is less than 2,150 lux(equivalenttowhatcuttingswouldreceiveonaverageduringcloudyweatherinsummer)

• MostHNSsubjectsshownofurtherincreaseinrooting percentage in light levels above 3,250 lux

• Some subjects have higher light requirements (upto8,100lux);theseusuallyhaveasmallleaf area relative to stem thickness, such as Berberis x stenophylla

• As light levels increase, more moisture is required toavoidareductioninrootingduetowaterstress

• At a given light level, subjects vary greatly in their moisturerequirement.Thelargertheleafareapercutting, the greater the moisture requirement tends to be

• Rottingisnotareliablesymptomofoverwetting; itcanoccurwhenthereistoolittlemoistureandalmostalwaysoccurswhenthereisnotenoughlight

• Manydifficulttorootsubjects(includingCotinus coggygria ‘Royal Purple’, Garrya elliptica, Syringa) havehighrootingpotentialbutanarrowrangeofenvironmentsinwhichthatpotentialisexpressed

• Easy-to-root subjects are those that tolerate anunusuallywiderangeofenvironments,oftenincludingverylowlight

• Therootingenvironmentcanaffectsubsequentgrowthand,thus,thequalityoflinersandcontainerplants,especiallyinslowergrowingplantsthatdonot require much pruning to create a desirable shape

These general conclusions can be combined to optimisetherootingenvironmentofHNSsubjects and so provide a good foundation for all subsequent stagesofproduction.Exampleactionpointsinclude:

• Innurserysituationswherelightisoftendifficult to precisely control, aim for slightly higher light levels than the minimum acceptable and provide correspondinglymoremoisturetoavoidwater stress.Fogandmistcontrollersmustincrease outputasthelightlevelincreasesifwaterstress is to be minimised

• Forplantswithahighmoisturerequirement,supportive high humidity rooting environments shouldbeused;leafwettingalonewillusually notbesufficienttoavoidmoisturestressand, in turn, poor results


• A suitable combination of high humidity and leaf wettingcanbeachievedwithfogorbyenclosingmistunderapolythenetent.

• Minimising ventilation to retain humidity leads to high temperaturesduringsunnyweathersoadequateshade is essential

Table14providesfurtherguidelinesrelatingtospecificHNSsubjectsintermsoftheirspecificenvironmentalrequirements.

Table13.LightandmoisturerequirementsofleafycuttingsofarangeofHNSsubjects

Environmental conditions Subject

High moisture requirement

Acer cappadocicum ‘Rubrum’Corylus maxima ‘Purpurea’ (apical cuttings)Corylus maxima ‘Purpurea’ (non-trimmed proximal cuttings)Cotinus coggygria ‘Royal Purple’Elaeagnus pungens ‘Maculata’Garrya elliptica‘JamesRoof’Pieris ‘Flaming Silver’Rhododendron‘Goldflimmer’Rhododendron ‘President Roosevelt’

Moderate moisture requirement

Acer palmatum ‘Aureum’Aubrieta ‘Red carpet’Aubrieta ‘Greencourt Purple’Cornus alba ‘Sibirica’Corylus maxima ‘Purpurea’ (leaf trimmed proximal cuttings)Ceanothus ‘Autumnal Blue’

Lowmoisturerequirement

Cryptomeria japonica ‘Elegans Compacta’Convolvulus cneorumDaphne x burkwoodii ‘Somerset’Potentilla fruticosa ‘Tangerine’

High light requirement Berberis x stenophyllaFremontodendron ‘California Glory’

Widely tolerantForsythia x intermedia‘Lynwood’Pieris japonica ‘Little Heath’Weigela florida ‘Variegata’

Table14.GuidelinesforthepropagationandgrowingonofspecificHNSsubjects

Subject Comments

Acer cappadocicum ‘Rubrum’ Nearly100%ofsoftapicalcuttingsrootinawetandhumidenvironment(‘wetfog’orclosedmist)

Aubrieta Despitebeingaplantthatcangrowindryconditions,cuttingsrooted best under moderately heavy mist

Corylus maxima ‘Purpurea’

Almost 100% rooting of apical cuttings is possible if leaves arekeptmoistandhumidityishigh.Wetfogorenclosedmistisideal,withabout20%ofavailablelight.Non-apicalcuttingscan also be used and tolerate slightly drier conditions

Cotinus coggygria ‘Royal Purple’ 100%rootingachievableinaverywetenvironmentatmoderate to high light

Cryptomeria japonica ‘Elegans Compacta’ Avoid environments that suppress transpiration too much

Elaeagnus pungens ‘Maculata’ Needshighhumidityandheavywetting

Fremontodendron ‘California Glory’Avoidexcessiveshade;duringsummer25%ofavailablelightshouldbesatisfactory.Ensuretherootingmediumiswelldrainedandavoidoverwetting

Garrya elliptica‘JamesRoof’Givenhighhumidityandgenerouswetting,nearly100%ofsoftapicalcuttingsroot.Fan-distributedfogisprobablyideal,with20%ofavailablelight

‘Flaming Silver’ Pieris Rootsbestfromsmallcuttingsunderwetconditions(fogorclosed mist)


Mist and high humidity environmentsEarly mist systems aimed at providing a continuous supplyoffinemistinthepropagationhouse,aprecursorperhapstowhatbecamebetterknownasfogorhighhumiditypropagation.Theprincipaldifficultywithcontinuousmistwasthatitappliedmorewaterthanwasrequiredforrootingleafycuttingsandwas,infact,detrimental.Assuch,various systems of control evolved, from the use of simple time clocks, through devices called ‘evaporating pans’,towhatbecameknownasthe‘electronicleaf’,eachofwhichservetobreakanelectriccircuitinordertocontroltheon-offperiodofthemisting.Thelatterare,ofcourse,notwithoutdifficultiesandsincethenlight sensors have been used and, most recently, the EvaposensordevelopedatNIABEMR.Mistpropagationdiffersfromfogginginthatmistingproduceswaterdropletswithaconsiderablygreatersizerangeinwhichmostarelargerthan50microns.Suchlarge droplets have minimal suspension properties and falloutoftheair,leadingtocuttingsbecomingwaterstressedifthefilmofwateronthefoliageisincompleteandhumiditydropsbetweenmistbursts.Overwettingof the rooting medium can also occur, underlining the needforgoodcontrolofthemistunit.Despiteprogresswithhighhumidityfogpropagation,mist units remain the main system used by the industry for the rooting of cuttings, particularly during the spring andsummerperiod.

The mist environmentTheprincipalfunctionofmististowetthefoliageofcuttingsandminimisetranspirationalwaterlossbyraisingthevapourpressuredeficitmicroclimatearound the leaf stomata and by using the evaporative coolingeffectofleafmoisture.Topreventwaterstressin cuttings, the vapour pressure inside and outside the leaves should, ideally, be at the same point, and high humidityenvironmentshelptoachievethis.Turgidcuttings root better and quicker than cuttings that are allowedtowilt.Mistalsowetstherootingmediumsufficientlyforrootinitiation.When correctly set up and managed, mist propagation providesleafycuttingswithidealconditionsthroughouttherootingprocessandsoenablesquickrooting.Good ventilation and shading to control air temperatures andlightlevelsisimportant,particularlyinsummer.Bright sunshine quickly scorches soft cuttings and high temperatures reduce atmospheric humidity, leading to moisture stress in the cuttings and excessive extension growth,whichmobilisescarbohydratesattheexpenseofrooting.Veryhighlightintensitiesalsoleadtoanexcessivebuild-upofcarbohydrateswithincuttings,whichcaninhibitrooting.Preferredairtemperatureswillvarywithsituationbut12–15°Cwillusuallysuffice,ventilatingat18–21°C,althoughsomereferencessuggest25°C.

Most heat is required at the base of cuttings for rooting and not in the aerial environment, aside for frostprotectioninwinter.Optimumbasaltemperaturesvarywithspecies.Atonepoint,21°CwaswidelyrecommendedforHNSbutthisiscostlyandmanysubjectsrootreadily,butalittleslower,atlowertemperatures(around15–18°C)orevenwithoutbaseheat, for example, many conifers and easy rooting shrubs.Thestandardrecommendationis18–24°C.Excessivemistingwilloverwetcuttingsanddepletetheir nutrient reserves by leaching and should be avoided.Whilethiscanbeoffsetbyfoliarfeedingor‘fertigation’ via the mist lines and the use of controlled release fertilisers in the rooting medium, cuttings can still deteriorate, underlining the need for good mist control.Overmistingalsoleadstowaterrun-offfromcuttings, saturating the rooting medium and reducing thebasetemperature.Rootedcuttingsshouldbeweanedoffandremovedfromthemistpromptly,otherwisetheycanquicklydeteriorateasaresultofnutrientleaching.Rootingthroughintosandbeds, canalsooccur,leadingtosubsequentgrowthchecks.Asuitableairtowaterratiointherootingmediumiscriticalundermistand,whilemoistureinputcanberegulatedthroughefficientenvironmentalcontrol,gooddrainageinthetraysandbedsisessential.Goodwaterqualityisessentialformisttoworkwell.Watermustbecleanandrelativelysoftashardwatercreatesunsightlylimescaleoncuttings,whichimpedesphotosynthesis, raises substrate pH over time and leads tonozzleblockages,therebyreducingefficiencyof themist.

Setting up a mist unitMist units can be set up in polythene tunnel structures or glasshouses, preferably the latter as they are usually easiertoventilatetocontrolsummertemperatures.Theyalso tend to be less humid and have a more buoyant, easilycontrollableatmosphere.Benched mist systems have the advantage of easy accessandvisibility,particularlywheninspectingandpickingovercuttingsbutfloorlevelbedsareusuallycheaper,makegooduseofspaceandaremorewidelyused.Ideally,bedsandbenchesshouldbearound1.2mwidetoenablecuttingstobeeasilyreachedinthecentre.Typically,suchbedsorbenchesarelinedandofacapillarysandbedconstruction.Sometimes,thebedsarealsocoveredwithapermeablemembranetocontrolweedsandrootingthrough.Suchsurfacesareusuallymore hygienic and easier to keep clean but can restrict capillarycontactanddrainage.The beds or benches should be insulated around the sidesandbasewith5cmpolystyrene,wrappedinplasticforheatconservation,especiallywherebaseheatisused.Heatingcablesarestillusedtoprovideheat although there is some use of heat foils and underfloorheatingusinghotwaterpiping.Cablesarenormally laid on a bed of sand or gravel, to a depth of 10–15cm,allowinga5cmspacebetweeneachloopof


thecables.Wirenettingplacedoverthecablesprovidesusefulprotectionandhelpsspreadtheheat.Modernsensors placed in the rooting medium near the base of thecuttingsprovidetemperaturecontrol.

Basal heat provided by screened heating cables

Basalheatprovidedbypipedhotwater

Atonestage,openplanporousconcretefloorswereusedwithalkatheneheatpipesunderneaththesurfacebutthesearenowlesscommononaccountoftheirhighcost.However,theyofferexcellentspaceutilisation,flexibility,readyaccess,strength,energyefficiency,cleanlinessandeasymaintenance.The layout of the mist jets varies but usually they are either attached to standpipes arising from the base of thebedorsuspendedabovethebenchorbed.Either

way,eachofthejetsmustbeatthesamelevel.Whiledifferenttypesofmistjetarenowavailable,mostproduce a circular spray pattern, such patterns should overlaptoavoiddrycorners.Mistheadsshouldberuninasinglelinedownthebedsorbenchesratherthanalternated,whichwasteswater.

Bedmistsystemwithrisers

Traditionally,anautomaticor‘wet’leafplacedbetweenthecuttingswasusedtocontrolthefrequencyofthemist but these have been superseded by time controls, lightsumsensorsand,mostrecently,theEvaposensor.Mist units should be serviced regularly to maintain theirefficiency.Mistingjetsshouldnotbeallowed tobecomeblocked;theyshouldberemovedandcleaned at least annually and any probes and mist controlequipmentinspected.Propagation programmeMist facilities can be expensive to set up and run so tobecost-effectivetheyneedtobeusedthroughouttheyearoratleastmostofit.Usinganaveragerootingperiodoftwotosixweeksdependingonspecies,itisfeasible to put six to eight batches of cuttings through amistunitduringayear.However,thereislikelytobeapeak during the April to August period requiring careful managementandpromptweaningofrootedmaterial.Forcing stock plants enables earlier cuttings to be taken, for example, of subjects such as Acer palmatum, deciduous Azalea, Clematis, Cotinus, Exochorda and Syringa,andhelpstoevenoutpeaks.ManyHNSspecies can also be readily rooted throughout the autumnandwinterperiod,includingevergreenspeciesandmanyconifers.Grey or hairy-leaved subjects such as Senecio(syn.Brachyglottis), Santolina and Lavandula dislike continuallywetfoliageandusuallyrootwellunderpolytheneorglass.Whilemostnurserieswillhavetheirownmistpropagationprogramme,anexampleisshownoverleafinTable15.


Table15.Yearroundmistpropagationprogramme

Month Subjects

JanuaryEvergreensandconifers,e.g.Chamaecyparis, X Cupressocyparis leylandii, Ilex, Mahonia, Thuja,etc.

FebruaryEvergreensandconifers,e.g.Chamaecyparis, X Cupressocyparis leylandii, Ilex, Mahonia, Thuja,etc.

MarchEvergreens,conifers,softwoodcuttings(forced),e.g.Acer, Azalea, Cotinus, Exochorda, Syringa,etc.

April Softwoodcuttings(forced)continued

May Softwoodcuttings,shrubs,climbers,alpines,herbaceous

June Softwoodcuttingscontinued

July Softwoodandsemi-ripecuttings,e.g.Choisya

AugustSemi-ripecuttings,e.g.Azalea (evergreen), Camellia, Ceanothus, Eleaegnus, Garrya, Hydrangea, Viburnum tinus,etc.

SeptemberSemi-ripecuttingscontinued,e.g.Choisya, Ceanothus, Elaeagnus, Garrya, Pyracantha, Skimmia, Viburnum,dwarfconifers,etc.

October Semi-ripe cuttings continued, evergreens and conifers

November Semi-ripeandhardwoodcuttings, e.g.Juniperus, Taxus,etc.

December Semi-ripeandhardwoodcuttings, e.g.Juniperus, Taxus,etc.

The fog environmentFoggingisthedistributionofverysmallwaterdropletsthrough the propagation environment to create a constantly high humidity, usually in the order of 95–100%.Itsprincipalobjectiveistoproduceahighhumidityenvironmentwithoutoverwateringtherootingmedium or leaching nutrients from the foliage of cuttings,acommondifficultywithsomemistsystems.The more constant humidity of fog also helps avoid the cyclichumiditypatternsassociatedwithmist,whichcanstress unrooted cuttings, particularly those of a soft, leafynature.Assuch,foggingisprimarilyaspringandsummersystemintheUKandisespeciallyusefulfortheearlyseasonrootingofmoredifficultplantsubjects.Theair-bornewaterdropletsthatcreatethefogareminute(typically,downto10micronsorlessinsize)and their dispersal raises the humidity of the aerial environmenttothepointwherethereisanexcessofwaterdropletssuspendedintheair,hencetheterm‘fog’.Suchdropletsfloatratherthanfallfromtheairand, because of their large surface area to volume ratio, theyreadilyevaporateandcooltheair.Theyalsocreateandmaintainaverythinfilmofwateroverthecompletesurface area of the cutting, cooling the surrounding airandreducingtranspirationalwaterlossastheyevaporate.

Fogging systemsFogging equipment is usually based on one of the followingsystems:

• Ventilatedfog(centrifugalsystem).Withthissystem,largevolumesofairaredrawnbyafanacrosswaterbroken into small droplets either by centrifugal force alongspinningrodsoraspinningdisc,andblownthroughthepropagationarea.Thisapproachconfersthe advantage of cooling but uses relatively large volumesofwaterofvaryingdropletsizes,whichproduces a marked gradient in relative humidity and canoverwaterduetofall-outnearthefoggingunitaswellascreatingconsiderableairturbulence. Assuch,theyarelesssuitableforweaningmicropropagatedmaterial.Thissystemisusually the cheapest method of fogging, no compressor being required

• Pressurisedwaterfog(highpressuresystem). Thisfogisproducedbyforcingwateratveryhighpressures through micro nozzles from overhead suspendedlines.Theyareusuallymoreexpensivebut produce a uniform fog of small droplet size (10 micron) capable of suspension in the air

• Pressurisedair/watersystems(lowpressure/pneumaticsystem).Inthissystemcompressedairandwaterarebroughttogetherinspecialisedjetscreatingashockwavethatdisruptsthewaterandproducesrelativelyfinedroplets.Theindividualnozzles and associated compressors can be relatively expensive

Control systemsSuccessful fogging depends on good control to maintain the requisite humidity levels and avoid over foggingand,inturn,excessivelywetfoliage.Excessivefoggingleadstocoalescenceofthefinedroplets, fall-outandwetleafandrootingmediasurfaces, notunlikemist.Several control systems are available, ranging from simple timer units through to interval controllers that humidify the air for set periods, various types of humidistats and aspirated humidity controllers that are suitablefordifferentfoggingsystems.AtHRIEfford,atimeclockcontrolgavepoorresultsinthevariableweatherpatternsoftheUKand,whilethehumidistatsofthetimewereanimprovement,therewasatimelaginresponsetochangingconditions.Anelectronichumidistatabletomaintainaverynarrowrangeofhumiditiesgavethemostpromisingresults.

ShadingLeafy cuttings in a nearly saturated atmosphere lose waterveryslowly,althoughtranspirationalwaterlossdoesnotentirelystop.Lightfallingonleavesraisesleaf temperature above that of the surrounding air, suchthattheywilllosesomewatereveninafullysaturatedenvironment.Insuchahumidatmosphere,little of the light energy absorbed by the leaves is lost through evaporative cooling, so leaf temperature can


berelativelyhigh,evendamaging.Adequateshading,around 50% in the summer, to reduce light and heat andsoavoidwaterstressis,therefore,essentialinfoggedsystems.WorkatHRIEffordwithapressurisedair/waterfogsystemfoundthat,evenwitha55%permeableshadescreen across the propagation house, temperatures inexcessof35°Cwererecorded.Asonlylimitedventilationispossiblewithfogsystems,atHRIEffordupto20%ventontheleewardsideoftheglasshouseand10%onthewindwardsideprovedanacceptablecompromise.Despitethehightemperatures,cuttingmaterial appeared to acclimatise to the conditions androotedwell.

ResearchEarlyworkatHRIEffordcomparingfoggingwithmistfor summer and autumn propagation indicated faster rootingandearliergrowthfromcuttingsrootedunderfog.Cuttingqualitywasalsobetterasfoliageleachingwasreduced.FurtherworkattheformerGCRIfoundthatthestomataonleavesoffoggedcuttingsweremoreopen than those under an open mist, so that entry of carbondioxideforphotosynthesiswaslessrestricted.Consequently,foggedcuttingsgaineddryweightfaster,inspiteofreducedlight.Theirwaterbalancewasalsoslightly superior to that of cuttings in closed mist and considerablybetterthaninopenmist.Whilepreviousstudieshadshownthatrootinitiationseldomrelatestodryweightgain,insummer,cuttingswiththebestwaterstatususuallyrootfasterandtoahigherpercentage.Rootingtrialswith‘wet’(closedmistandfog)and‘dry’ (open mist) systems at GCRI using a pressurised air/waterfoggerfoundthatconifers(Chamaecyparis lawsoniana ‘Tamariscifolia’ and X Cupressocyparis leylandii ‘Robinson’s gold’) and broadleaf evergreens (Buxus sempervirens)performedlesswellinfogthan inopenmist.However,fogproducedbetterrootingamong soft leafy cuttings of subjects such as Acer palmatum, Cotinus coggygria, Cornus alba and Magnolia x soulangiana than open mist and similar, rootingtoclosedmist.

Merits and limitations of fogging systemsThe merits and limitations of fog propagation relative to mistcanbesummarisedasfollows:Merits• Larger cuttings may be rooted, particularly those

cuttingswithlargeleafblades,asfogginghasbeenfound to keep cuttings in better condition until rooting has occurred

• Cuttingscanbetakenearlierintheseasonwhensofter and easier to root, due to the more supportive, higher humidity environment provided by fog

• Rootingissometimesfaster,withhigher percentage takes

• Premature leaf-drop due to nutrient leaching and waterstressislessenedcomparedtomist

• Rootingmediaislesslikelytobecomewaterlogged(reducingtheprospectofcuttingsdamping-off)

• Significantlylesswaterisrequiredandwaterparticles are more evenly dispersed

• The high humidity environment created by fog is moresupportivethanmistandsoidealforweaningmicropropagated material

Limitations• Achievinguniformdistributionoffinefogdroplets

canbedifficultandmarkedvariationsinrootingandcutting survival can occur, although researchers at HRIEffordfoundthatliningtheirpropagationhousewithpolythenereducedtherateoffogdispersion.Installing ancillary ventilation fans to gently move the fog around may also help

• Controllinghightemperaturescanalsobedifficultasfogisessentiallyaclosedsystem.Thiscanbeaparticular problem in non-ventilated systems, underlining the need for adequate shade screening in summer.Ventilatedhighhumidityfoggingunitsthatdrawcoolairintothepropagationareaandcontinually replenish the moisture content of the air enableventilationtotakeplace.Assuch,thecombinationofcoolairandventilationcreateslowerambient temperatures

• Generally, fog is a less comfortable environment to workinduetothehighhumiditiesandtemperaturesalthough high pressure systems capable of producingwaterdropletsof10micronsinsizecreatea‘dry’fogwhichismorecomfortable(suchsystemsarealsomoresuitableforwinterpropagation)

• Onlywaterdrawnfromaclean,directmainssupply(avoiding storage tanks) can be used, to help safeguardstafffromcontractingLegionella via inhalationofthefog.Enclosingfogunitswithin high polythene tents provides a further safeguard

• Rootedcuttingsrequireearlierweaningto preventgrowthbecomingdrawnandsoftunder high temperatures

AftercareIn high humidity environments such as mist or fog, Botrytis infection of leafy cuttings can readily occur andrequirespromptcontrol.Althoughventilationandwell-controlledmistenvironmentsthatreduceoverwettinghelp,cuttingsshouldbecheckeddailyandanydecayingmaterialremovedpromptly.Fungicide sprays may also be required to control disease outbreaks, although a routine programme is seldomjustifiedifthemistenvironmentiswellmanaged.Weaning should start once cuttings are adequately rooted,rootsshouldbeatleast2cmlong.Usually,themist is either reduced gradually or the rooted cuttings areremovedtoaseparateweaningbed,benchorhouse, to enable the continued rooting of other cuttings inthemist.


Once fully rooted and acclimatised to ambient conditions,thecuttingsmaybetransferredelsewhere toawaitsaleorpottingon,unlesstheyhavebeen directstruckintofinalcontainers.The inclusion of controlled release fertilisers in the rootingmediumbecamestandardpracticefollowingsuccessfultrialsatHRIEffordandprovidesimportantpost-rooting nutrition to maintain cutting quality until potting,althoughpreformedplugswithcontrolledreleasefertiliserarenowwidelyusedtoo.Similarly, the timely application of soluble feeds helps maintain cutting quality, including the use of high phosphate feeds ahead of potting to trigger root developmentandso,inturn,rapidplantestablishment.Crucially, cuttings must not become starved or rootboundotherwiseplantqualitywillsufferandestablishmentwillbemuchslowerfollowingpotting.

The role of the EvaposensorEvenwithwell-managedmistorfogsystems,waterstress among leafy cuttings may still occur if the control system, usually based on a timer, electronic leaf or measurement of solar radiation, fails to adequately match the misting or fogging frequency tothevaryingneedsofthecuttings.The Evaposensor, developed by Dr Richard Harrison-MurrayatNIABEMRasaresearchtool for controlling mist and fog environments, possesses wetanddryartificial‘leaves’,enablingthedetection and control of the evaporative demand on cuttings inareliableandreproducibleway.Crucially,itenablesoptimumconditionstobequantifiedandreproduced inawaythatisnotpossiblewithanyothertypeof mistcontrol.AtNIABEMR,itcontributedtothesuccessfulpropagationofdifficult-to-rootHNSsubjects,including Acer cappadocicum, Acer palmatum cultivars, Corylus maxima, Cotinus coggygria, Garrya elliptica and some Pieris and Rhododendroncultivars.Ithassincebeencommercialised and has been available for use by growersformanyyears.TheEvaposensorconsistsoftwotemperaturesensing‘leaves’ containing platinum resistance temperature sensors.One‘leaf’remainswetviaawickconnectedtoadistilledwaterreservoirandtheother‘dryleaf’iswettedperiodicallybyburstsofmistorfog.Itispositionedjustabovetheheightofthecuttings,whereitisinfluencedbythemist/fog,solarradiation,airtemperature, humidity and air movement – all the factorsthatnormallyaffecttherateoftranspirationalwaterlossfromcuttings.It requires an interface electronic controller to enable outputfromthewetanddry‘leaves’totriggermistorfogbursts,eitherinconjunctionwithexistingtimersorasastandalonecontroller.

TheEvaposensorworksinthefollowingway:

• The‘wetleaf’isgenerallycoolerthanthe‘dryleaf’due to evaporative cooling

• Thetemperaturedifference(°C)betweenthetwo isknownasthewetleafdepression(WLD)

• WLD is proportional to potential transpiration and sopotentialwaterstressoncuttings

• Duringmistingorfogging,the‘dryleaf’becomeswetandtheWLDfallstonear0°C,mimickingtheeffectof mist on transpiration

• After a burst of mist or fog, as the ‘dry leaf’ dries out, the WLD rises until the set point on the controller is reached and another mist or fog burst is triggered

• The WLD set point (the maximum WLD before a mist burst occurs) represents a level of cutting support thatcanbereproducedacrossdifferentfacilities,nurseriesandseasons.DifferentHNSspeciesmayrequiredifferentsetpointsbutacompromisesetpointisrequiredwhereawiderangeofsubjectsisinvolved,particularlywhensharingthesamepropagation bed

The system applies the amount of mist or fog needed to limit transpiration to the level set on the controller, taking intoaccountthebackgroundenvironment.

TheEvaposensorhelpsdetectandcontroltheevaporativewaterdemandoncuttingsinareliableandreproducibleway

Research involving the EvaposensorAHDBHorticultureprojectHNS159:Nursery stock propagation: Nursery evaluation and demonstration of the Evaposensor towards its commercial availability as a mist controller, evaluated the technical performance of the Evaposensor on commercial


nurseries against their existing mist control systems and sought to develop an electronic interface to enable the technologytobecommerciallyadopted.ThecomparativeperformanceoftheEvaposensorwasalsotestedintermsofrootingleafycuttingsofarangeofHNSsubjects.Trial treatments and effects on the rooting of cuttingsInthefirstyearoftrials(2007–2008),theEvaposensorwascomparedwiththechosennursery’sown timer-based control system and, throughout the trial,itmaintainedconsistentlylowstress(lowWLD)environmentscomparedtothetimersystem,where theWLDfluctuatedsignificantly.The evaluation of the Evaposensor and interface controllercontinuedinyeartwo(2008–2009),withawiderrangeofHNSspeciesonanadditionaltwonurserieswithdifferentambientenvironments.Formanysubjects,rootingresultsweresimilarbetweenthe Evaposensor and timer control (averaging 77% for theformerand74%forthelattersystem).However,some subjects (notably, Berberis darwinii ‘Compacta’, Hydrangea petiolaris, Prunus cerasifera‘SpringGlow’,Solanum crispum ‘Glasnevin’, Spiraea arguta, Spiraea japonica‘Goldflame’,Tecrium fruiticans ‘Compactum’ and Viburnum sargentii‘Onondaga’)didbenefitfromthe, typically, higher amounts of mist provided via the Evaposensorandgavenoticeablyimprovedrooting.SomesubjectsrootedslightlylesswellundertheEvaposensor treatment, including Convulvulus cneorum, Ceanothus (various cultivars), Eleaegnus ‘Quicksilver’ and Halimiocistus sahucii.Asaresultofthewiderangeofsubjectsincludedundereach of the mist environments, the treatment set points werealsounlikelytobeoptimalforallofthem.Year one conclusions (2007–2008)• The automatic adjustment of mist to light,

temperatureandhumiditywasconsideredagreatadvantage.Itwasalsoacceptedthatthemanualadjustment of timer settings can never be as effective.AlthoughtheEvaposensorappliedmoremist to the cuttings, it crucially applied less mist duringdullorcoolweatherconditions

• Whiledifferentsetpointsmayberequiredforoptimumresultswithdifferentspecies(theoneusedinthetrialwasacompromiseforthewiderangeofsubjects involved on the same bed), it can be used morereliablybydefiningaWLDsetpointthatautomaticallytakesaccountofweatherchangesanddifferingambientaerialenvironmentsbetweenpropagation units

• WherearangeofHNSsubjectsisinvolved, a1–1.5°CWLDsetpointontheEvaposensorinterface or controller is likely to be a good starting point(usingamistburstofaroundtwoseconds)

• TheEvaposensorshowedconsiderablepromise asaflexibleanduser-friendlysystemforcontrollingmist in propagation environments

Year two conclusions (2008–2009)During this phase of the project, the Evaposensor controllerwasdevelopedfurther,suchthatitwasavailableasacommercialproduct.

• Subjectsshowingasignificantimprovement(over10%) in rooting included Ceratostigma willmotianum ‘Forest Blue’, Choisya ternata, Escallonia (various cultivars), Halimium, Olearia cultivars, Pittosporum tenuifolium, Prostanthera cuneata and Vinca minor cultivars

• ThosethatrootedlesswellundertheEvaposensorincluded Convulvulus cneorum, Halimiocistus sahucii, Prostanthera ‘Mint Royal’, Rhamnus alaternus ‘Argenteovariegata and Weigela ‘Red Trumpet’

• Overall,themostsignificantpercentagerootingbenefitsoccurredwherethestandardsystemfailedtoapplysufficientmistduringhighevaporationdemandperiodsandcuttingswerestressed,althoughsomesubjectsdislikedtheextrawettingapplied to foliage by the Evaposensor during hot conditions, including Convulvulus cneorum and Halimiocistus sahucii(specieswithhairyordownyleavesarelikelytoholdwaterforlongerandsobenefitfromadrierregime)

• Formostsubjects,therewerenoobviouslylargedifferencesintermsofspeedofrooting,althoughatonenurserysite,withseveralsubjectsincluding:Artemisia‘PowisCastle’,Cistus‘MaySnow’,Euonymus japonicus ‘Duc d’Anjou’ and Vinca minor ‘Illumination’(alltwotothreeweeksquicker)andEuonymus fortunei ‘Harlequin’ and Polygala myrtifolia(sevenandeightweeksquicker,respectively),therewasclearevidenceoffasterrooting under the Evaposensor regime

• Moreshootgrowthfromplugswasalsoobserved in the Evaposensor treatment for these and other subjects during and shortly after their time under the mist

Commercial testing and developmentThe development of a commercial mist control unit harnessed several features that enhanced the versatility oftheEvaposensor;itcouldbeusedeitherasastandalone controller operating a single solenoid valve or be linked to an existing timer or sequencer to control multiplebeds.TheEvaposensorwastestedatthreecommercialnurseriesaspartofAHDBHorticultureprojectHNS 159a: Promotion and dissemination of Evaposensor sensor mist control on nurseries, and proved easier tomanage,comparedtothetraditionalwetleafmistcontrolnormallyusedattwoofthesites,whichtendedtoapplytoomuchmist.Atthethirdnursery,the Evaposensor also required less adjustment and providedaneasiertomanageenvironmentforweaningmicropropagatedmaterialcomparedwiththeirusuallight-sumsystem.


Experience on the third nursery site did not suggest thattheEvaposensorwasanimprovementontheirexistingmisttechnology.However,inthiscase,averydryregimewasfavoured,partlyinresponsetotherangeof plant material produced and partly because of a lack ofapositivelydrainedstandingbase.Asophisticatedmist control regime based on light-sum and humidity, using a climate control computer had already been adoptedbythenursery.Evaposensormistcontrollersarenowavailabletogrowers,whichfeatureadigitaldisplayofWLDtoindicate current status, built-in timers for the control of both the burst length and the minimum interval betweenbursts,andastandalonemistcontrolleror aninterfacetoexistingequipment.Ananalogueoutput,whichexpandstheoptionsofintegrationwithotherequipment, had already led to success in automatic schedulingofirrigation.Duringnurserytesting,staffreadilygraspedthebasicconcepts of Evaposensor control and the mist control unit.SomenurserieswerecontenttoleavetheWLD set-pointalone,allowingtheEvaposensortocompensateforday-to-dayvariationsinweatherandseason.Otherspreferredtoexploittheconvenienceofthecalibratedsetpointcontroltofine-tuneconditionstosuitparticularspecies,season,stageofrooting,etc.Where capillary drainage is limited or a particularly dry regime is required, the ‘interval’ control can be useful tosetanupperlimitonmisting.

Financial benefitsAnyfinancialbenefitsprimarilydependonthescale of overall improvement in the percentage of useablecuttingsproducedandanysavingsinlabour.Otherbenefitsarelessstraightforwardtocalculatefinanciallybutstillhaveamonetaryvalue,suchas

easeofmanagement,abilitytorelylessonskilledstaff(especiallyforweekendorholidaycover)and theopportunitiesforpropagatingnewordifficultcultivarsthatwouldotherwisehavetobeboughtin.So far as labour savings are concerned, assuming an average 12% increase in rooting is achieved, for a propagation unit producing some 200,000 cuttings perannum,around£1,000/yearcouldpotentiallybesavedfromwastedinputs(includingpreparationandhandlingofcuttingsnotrooting).Or,consideredanotherway,a12%increaseon200,000linerswithanaverageunitvalueof75pwouldequatetoanincreaseofapproximately£18,000infinancialoutput.

Polythene systemsManyHNSsubjectscanberootedwithoutmist,usingsimple polythene systems, usually, but not necessarily with,baseheat,particularlyduringtheautumnandwinterperiod.Typically,thepolythenecoverissuspendedoverahooporframetoprovideanairbufferaround the cuttings, but it can be placed directly over thecuttingstoo(warmbenchandplasticsystem).Benchesorfloorlevelbedsareusedandconstructedinmuchthesamewayasamistsystem.Infact,somegrowersdeployahybridofthetwo,usingwell-shadedclosed mist system for summer propagation of soft leafy cuttingsandpolythenewithoutthemistfortheautumnandwinterrootingofevergreensandconifers,whichpreferadrierregime.Fleececoversareoftenusedforadditionalshadeorheatretention.

Warm bench and plastic systemWiththissystem,thecuttingsaredirectlycoveredwithathin(around20–25micron)transparentpolythenefilmfollowinginsertion.Usually,thesheetisclearbut

Case study 5: P&S Nursery Stock

Fine tuning mist propagationP&SNurseryStockinCambridgeshireproducesawiderangeofpotlinersandplugplantseachyearforsaletothetrade.Muchofthepropagationworkis undertaken during the spring and summer months using soft and semi-ripe leafy cuttings rooted under open mist, although some species are struck during theautumnandwinterperiod,mainlyevergreens.Twoopenmistbedsareused,oneeithersideofacentralpathway,inawalk-inpolythenetunnel,shadedduringthesummermonths.Mostrootingisdone in plug trays using a ready-mix rooting medium ofcoir,barkandperlite,withapowderhormonetreatmentforthecuttingsinmostcases.Whilemisthasusuallyworkedwellforthenursery,recurringdifficultieshadbeenencounteredwithoverwetting(despiteelectronicleaf,timerandlightsensor

controllers being tried), resulting in the rotting of cuttingsleadingto,insomecases,heavylosses.In a further attempt to match misting frequency closertotheneedsofthecuttings,reflectingmore accurately changing light levels, humidity, temperature and air movement during the day, thenurserytrialledanEvaposensorwithsummerpropagationduring2010,havingfollowedHNS159andearlierworkatEMRwithinterestandbeenencouragedbytheresults.Sofar,theEvaposensorhasdeliveredgoodresults,followinginitialteethingproblemsoffindingtheappropriateWLDsetpoint,giventhewiderangeofHNSspeciesbeingrootedatanyonetimeonthesamebed.NurseryownerPaulMcKarrycomments,“Itwouldbe hard to say the Evaposensor has made a radical changetoourmistpropagation,however,ithasgiven better control over the system in terms of leaf wettingandlessoverwettingofrootingsubstrate.Rootinghasincreasedingeneralby10–20%.”


awhitefilmisnecessaryforsummerpropagationunlessshade screening or netting is used (these may also be necessarywithawhitefilmduringverybrightperiods).Shadingisinfactusuallyrequiredfromlatewinteronwards,asevenlowsunlightcanquicklyincreasetemperaturesunderthefilmtodamaginglevels. Amaximum-minimumthermometershouldbesetwithinthecuttingsfortemperaturemonitoring.Theedgesaresealedusinglathsorbytuckingthefilmunderneaththeplugtraysorpotsusedforrooting.

Contact polythene quickly ‘fogs up’ once cuttings are covered to create the humidity required for successful rooting

Oncedrawnoverthecuttings,thefilmquickly‘fogsup’withcondensatesuchthatthecuttingsbecomeenclosedwithinasaturatedatmospherethatpreventsthemwilting.Mostrecently,thecommercialfilmXLThermaProphasbeendevelopedforHNSpropagation,whiteforsummerandclearforwinteruse.Thismaterialcombinesheatretentionandeventemperaturedistributionwithaninternalanti-dripcoatingtoavoidoverwettingofcuttings.Whilethissystemoffersausefullowcostalternativeto mist propagation, particularly during the autumn andwinterperiods,itdoesdemandespeciallycarefulmanagement.Shadingiscrucialandcuttingmaterialshouldbecheckeddaily.Decayingcuttingsmustberemovedpromptly,otherwise Botrytiswillquicklyfollow.Thefilmshouldbepeeledbackregularlyforadetailedinspectionandtoventthecuttings.Once rooted, usually in plug trays, the cuttings should beweanedbygraduallyslittingorremovingtheplasticfilm.Thismustbedonecarefullyassuddenexposuretobrightsunwillleadtodryingoutanddeteriorationofthecuttings.Alternatively,rootedmaterialcanbemovedto another bed to enable the continued rooting of later struckcuttings.Baseheatisgraduallyreducedasweaningprogresses.Somepropagatorsfeelthatcuttingsrootedinthiswayremain in better condition than those rooted under mist, due to an absence of nutrient leaching, although they canbeslowertoroot.Table16(overleaf)listsarangeofHNSsubjectssuitableforwarmbenchandplasticpropagation,whileTable17(overleaf)comparesandcontraststhewarmbenchandplasticsystemwith mistpropagation.

Polythenetentsystems,wherebythepolythene(orfleece)israisedabovethecrop,areusuallyeasiertomanagethancontactpolythene


Table16.HNSsubjectssuitableforcuttingpropagationunder awarmbenchandplasticsystem

Month Subjects

JanuaryVarious conifers, including: Chamaecyparis, Cupressus, X Cupressocyparis leyandii and Juniperus,etc.

February

Conifers continued, also various evergreen shrubs, including: Elaeagnus, Garrya, Ilex and Rhododendron(dwarfspeciesandcultivars),etc.

March Conifers and evergreens continued

April Deciduous shrubs including: Azalea, Magnolia,etc.

May Deciduous shrubs continued, including: Azalea, Magnolia, Cotinus,etc.

June

Deciduous shrubs continued, including: Cornus(dogwoodspecies)Cotinus, Deutzia, Forsythia, Hypericum, Philadelphus, species roses,etc.

July

Deciduous shrubs continued, including: Magnolia, Pieris, Ribes, Spiraea etc. Some evergreens including: Azalea, Camellia,, Cotoneaster, etc.

AugustVarious deciduous and evergreen species, including: Azalea, Camellia, Cotoneaster, Pieris, Spiraea, Viburnum tinus,etc.

September Evergreens including: Azalea, Berberis, Camellia, Pyracantha, Viburnum,etc.

October Cupressus, Ilex, Mahonia, Pittosporum, Rhododendron (hardy hybrids), Thuja,etc.

NovemberBerberis (evergreen), Chamaecyparis, X Cupressocyparis leylandii, Cupressus, Ilex, Mahonia, Pittosporum, Thuja,etc.

December Various evergreens and conifers continued Table17.Advantagesanddisadvantagesofawarmbedandplastic system compared to mist propagation

Advantages Disadvantages

Cheaper and easier to install

Nonutrientleachingfromcuttings

More constant humidity pattern giving rise to less waterstress

Lessriskofoverwetrootingmedia

Suitable for a range of HNSsubjects,particularlyforautumnandwinterpropagation

Better quality rooting

Greater care and closer attention is required in relation to hygiene, shading andweaning

High summer temperatures can be a problem, especially withsoft,leafycuttings

Less suitable for spring and summer propagation of soft leafy cuttings

Slowerrooting

Low tunnelsAwiderangeofHNSspeciescanalsoberootedfromsemi-ripecuttingsunderlowpolythenetunnelssituatedoutdoors,toprovidewell-rootedlinerswithinayearfrompropagation.Thissystemiswellsuitedtocheaper,highvolumelinesasitislowrisk,lowcostanddoesn’trequirehighlyskilledlabour.Italsoenablesexpensiveheated,mistfacilitiestobeusedformoredifficultsubjectsandlinersproducedinthiswayareusuallystrongandsturdy,requiringlessweaningor‘hardeningoff’thanmistpropagatedmaterial.However,rootingisslowerandthereislesscontrolofgrowth,whichmaycomplicateschedulingrequirements.Thetunnelsareformedfromsimplegalvanisedwirehoopsusedtosupportopaquewhitepolythene(38micron), pushed into the ground (usually, to a depth of 30cm)at1mintervals,witheyeletstosecurethetyingmaterial.Doublehoopsareusedattheendsofthetunnelstoprovidegreaterstrengthwhenthepolytheneisstretchedtight.Thebedsareusually1mwideandofanydesiredlength, although very lengthy constructions hinder materialshandlingandaccess.Arootingmedium(typically,peatwithgritorbark)islaidoverthesoiltoadepth of 7 cm to form the beds and left loose to enable easyinsertionofthecuttings,althoughitcanbeworkedinto the soil as cuttings, are inserted to avoid it drying out.Usually,themixisthentoppedwitha2cmlayerof coarse sand or grit to ensure good drainage and aerationaroundtheneckofthecuttings.Lowtunnelsprovideafairlyhumidatmosphereandprotectionfromdesiccatingwinds.Thereislittleby wayoffrostprotection,althoughcropspropagatedinthiswayareusuallyhardy.Anoverheadirrigationlinecanbeincludedwithinthetunneltobolsterhumidityand provide post-rooting irrigation, particularly on light land but, for many crops, this is seldom necessary if thesoilisadeep,welldrainedbutmoistureretentivemediumloam.Shallowsoilsarebestavoidedastheycandryoutrapidly.Traditionally,cuttingspropagatedwiththissystemareclassifiedassemi-ripeandinsertedduringSeptemberandOctober(deciduoussubjectsearlier,inmidsummer).Awiderangeofmainlyevergreenbutalsosomedeciduous subjects can be successfully rooted using this system, including species and cultivars of: Aucuba japonica, Berberis, Buddleia davidii, Caryopteris, Cistus, Escallonia, Forsythia, Griselinia littoralis, Hypericum, Lavandula, Ligustrum, Lonicera pileata, Olearia x scilloniensis, Osmanthus heterophyllus, Philadelphus, Potentilla, evergreen Prunus species, Rosmarinus, Rubus, Santolina, Senecio(syn.Brachyglottis), Viburnum tinus and Vinca.Rooted deciduous material can usually be lined out or pottedfromautumnonwards,whileevergreenmaterialnormally remains in situ, to root through the autumn andwinter.


Sun tunnelsThe sun tunnel (so-called as it relies solely on heat provided by the radiant energy of the sun) evolved from thelowtunnelsystembutwasreviewedandimprovedatHRIEffordduringtheearly1980s.Essentially,itisalowtunnelwithanoverheadmistinglinetoincreasehumiditylevelsforsummerpropagationofsoftwood andsemi-ripecuttings.TheHRIEffordworkshowedthatearlierinsertion,lowercuttingpopulationsandimprovednutrition,usingcontrolled release fertilisers, largely overcame many of theproblemsassociatedwiththeoriginalconceptanddramaticallyshortenedthepropagationperiod.Thiscreatedopportunitiesforpropagatingawiderrange ofspeciesandforproducingbetterqualityplants.Suntunnelsareconstructedinmuchthesamewayaslowtunnelsbutwiththeadditionofanoverheadmistinglinealongtheridge(trialswithleafycuttingsshowed this to be more reliable than simply covering the cuttings withanextralayerofpolythene).Foradditionalirrigationof rooted cuttings, seep hose irrigation or similar is normallyused.DevelopmentworkatHRIEfforduseda50:50peat andsandmixwithcontrolledreleasefertiliser (1–2kg/m3ofa12–14monthproduct),incorporatedwiththe underlying soil to give a suitably textured rooting medium20cmindepth,abovesoillevel.Granulatedpinebarkcanalsobeused.ThemostsuitableHNSsubjectsforsummerpropagation under sun tunnels are deciduous shrubsthatrootreadilyfromsoftwoodorsemi-ripecuttings,takenbetweenlateMayandtheendof June,toenablemaximumgrowthinthefirstseason.Typically,cuttingsarearound10cminlength,withthelowerleavesremoved.Shoottipsandfloralbudsshould beremovedtoencouragewell-branchedgrowthoncerooted.Asageneralguide,cuttingsshouldbespacedat10cmx10cm.Thecuttingsshouldbecoveredwithopaquewhitepolythene (38 micron) that is secured to the sides by woodenlaths.Additionalprotection(20–30%shadenetting) is generally required to prevent scorching of soft orverysensitivematerial.Mistburstsneedtobewellcontrolledtoensurecuttingsdonotdryoutandscorch.AtHRIEfford,youngplantsestablishedandgrewawayearlierwhenlinedoutorpottedoninspringcomparedtothosetransplantedorpottedonthepreviousautumn.Thebenefitsofstrongerrootandshootgrowthandimprovedbranchingfrominsertionatawiderspacingwithcontrolledreleasenutritioninthesuntunnelscontinuedinthefield.Iftherootedcuttingsaretobeoverwinteredinsitu, thentheshadeclothorsuitablewindbreaknetting,should be placed back over the tunnel frame from lateNovemberonwardstoprovideadegreeofwinterprotection,especiallyfromcold,desiccatingwinds.Tender subjects are best lifted during the autumn, pottedandoverwinteredunderprotection.

Generally, for ease of handling and to promote furtherbranching,mostspecieswillrequiretrimmingbefore lining out or potting, and again during the growingseason.Table 18 overleaf outlines a generic annual production scheduleforHNSusingsuntunnels.TheHRIEffordworkalsoshowedthatarangeofevergreens and conifers could also be successfully rootedinsuntunnels(withthemistinglinereplaced by a layer of thin gauge clear polythene, supported just abovethecuttings)fromautumnorspringinsertions.Thereafter, the tunnel can be left undisturbed until the followingJune,asideofoccasionalchecksformoisture,weedsandrootingprogress.Awhitepolythenematerial(shaded in the summer) is used to cover the tunnel and seephoseorsimilarforpost-rootingirrigation.Oncesufficientrootinghasdeveloped(usuallyby midsummer), the inner cover can be removed to begin theweaningprocess,followedbythetopcovera fewweekslater,retainingtheshadenetasnecessarytominimiseplantstress.Well-rooted liners should then be ready for potting orliningoutintheautumn.Table19(overleaf)listsarangeofHNSsubjectsthathavebeenrootedsuccessfullywhentakenasearlysummercuttingsinsuntunnels.Other subjects successfully rooted on commercial nurseries from summer cuttings include: Berberis thunbergii atropurpurea‘Nana’,Ribes sanguineum ‘Pulborough Scarlet’, Rosa rugosa ‘Frau Dagmar Hastrup’ and Spiraea bumalda‘Goldflame’.

Thin gauge white polythene sheet stretched over hoop

Lath to hold polythene

in place

Mist unit

hanging below hoop

Sandy gritSeephose

600mm

200mm

1.25 m(SECTIONAL END VIEW (Not to scale))

Peat/soil/sandy grit

SuntunnelsareacosteffectivewayofpropagatingarangeofHNSsubjects


Table19.ProductionscheduleforsuntunnelsusingtheHRIEffordimprovedsystem

Summer cuttings (May to June insertion)

Azalea japonica‘BlaauwsPink’

Azalea japonica ‘Blue Danube’

Berberis darwinii

Berberis x ottawensis ‘Purpurea’

Berberis x stenophylla

Camellia x williamsii ‘Debbie’

Clematis montana

Cornus alba ‘Elegantissima’

Cornus alba ‘Sibirica’

Cornus alba ‘Spaethii’

Cornus stolonifera ‘Flaviramea’

Cotinus coggygira ‘Royal Purple’

Cotoneaster conspicuus

Cotoneaster horizontalis

Cotoneaster ‘Cornubia’

Cytisus x praecox

Deutzia scabra

Deutzia scabra ‘Plena’

Erica carnea‘SpringwoodWhite’

Forsythia‘Lynwood’

Hebe ‘Autumn Glory’

Hibiscus syriacus ‘Ardens’

Hydrangea macrophylla ‘Draps Pink’

Hydrangea macrophylla‘MadameJdeSmedt’

Hypericum calycinum

Hypericum ‘Hidcote’

Kolkwitzia amabilis

Lonicera nitida ‘Elegant’

Magnolia x soulangeana

Philadelphus ‘Burfordensis’

Philadelphus ‘Virginal’

Physocarpus opulifolius ‘Luteus’

Potentilla fruticosa‘KatherineDykes’,‘RedAce’and‘Tangerine’

Pyracantha‘OrangeGlow’

Ribes odoratum

Ribes sanguineum‘KingEdwardVII’

Rosa rugosa ‘Scabrosa’

Rhododendron ‘Cilpinense’

Senecio greyi ‘Sunshine’

Skimmia japonica ‘Foremanii’

Spiraea x billardii ‘Triumphans’

Spiraea nipponica tosaensis

Spiraea x vanhouttei

Stephanandra incisa

Stephanandra tanakae

Symphoricarpos albus

Symphoricarpos x chenaultii ‘Hancock’

Viburnum x bodnantense‘Dawn’

Weigela ‘Bristol Ruby’

Weigela ‘Eva Supreme’

Weigela florida ‘Variegata’

Weigela ‘Majestueux’

Autumn or spring cuttings (October or March insertion)

Berberis x stenophylla

Chamaecyparis lawsoniana‘Ellwoodii’,‘EllwoodsGold’,‘Allumii’, ‘Columnaris’ and ‘Stardust’

Chameacyparis pisifera ‘Squarrosa Sulphurea’

X Cupressocyparis leylandii(clone2)and‘Castlewellan’

Euonymus fortunei ‘Emerald Gaiety’, ‘Silver Queen’ and ‘Variegatus’

Ilex aquifolium‘HandsworthNewSilver’

Mahonia japonica

Olearia macrodonta

Osmanthus delavayi

Prunus laurocerasus ‘Otto Luyken’ and ‘Zabeliana’

Skimmia japonica

Thuja plicata ‘Zebrina’

Viburnum tinus ‘Eve Price’

Table18.ProductionscheduleforsuntunnelsusingtheHRIEffordimprovedsystem

April – May June July –

SeptemberOctober –November

December –January February March –

April

Bed preparation

Cutting insertion

Propagation (mist)

Liftingforfieldplanting or potting

Optional:Overwinteringin situ

Lifting for cold storage

Liftingforfieldplanting or potting


Cold frames with and without plasticManyconifersandevergreenHNSsubjects(asimilarlisttothosethatcanberootedunderlowtunnels)canbe rooted cheaply and successfully in cold frames from semi-ripe cuttings during the autumn, direct stuck into bedsofwell-drainedrootingmediumwithcontrolledreleasefertiliser,forliningoutorpottingthefollowingspring.Theycanalsobeusedforawiderrangeofsubjects, including the spring and summer propagation ofeasyrootingsubjects,withtheuseofthingauge(20–25 micron) polythene laid directly over the cuttings (forliningoutorpottingfromautumnonwards).Summershadingisessentialandfrostprotectionwill berequiredinwinter.Forwinterpropagation,theuse of plastic is unnecessary, although there are exceptions, notably, for example, X Cupressocyparis leylandii and Pittosporum.JunipersstruckduringAprilandcoveredwithplastic areknowntorootreadilywhenpropagatedincoldframes and are usually ready to come out during Juneforgrowingon,tobereplacedbyarangeofHNSsubjects.ShadingisespeciallyimportantwithAprilandJuneinsertions.Semi-ripecuttingsofLavandula also respondwelltodirectinsertionintocoldframesduringlateAugustandSeptember.Avariationofthecoldframewithplasticsystemisoneusingdoubleglazedframes,wherebytheframelights(usually, a standard ‘Dutch-light’ type) are insulated with38micronpolythene.Thecycleofpropagationfollowsthatofthecoldframewithplastic,startingwitheasy rooting evergreens and conifers during September andOctober.HNSsubjectsknowntorootwellatthistime in frames include Cotoneaster and Ilex species andcultivars,andawiderangeofconifers,includingChamaecyparis lawsoniana, X Cupressocyparis leylandii, Cryptomeria, Taxus and Thuja. Well-rooted liners of such material should be ready for lifting and growingonfromlatespringonwards,althoughJune is usually preferred for conifers, given they are often alittleslower.Semi-ripe cuttings of Juniperuswillnormallyrootwithin12weekswiththissystemandarangeofsemi-ripeshrubcuttingscanbestruckthroughoutJuneandJuly,forexample,Clematis, Cotoneaster, Hedera, Philadelphus, Viburnumandvariousheathers.Allcoldframesshouldbeconstructedonwell-drainedlandshelteredfromcold,dryingwindsandpreferablywithawarm,southerlyaspect.

Cuttings in the open groundThis is a relatively easy method of propagation from mainlyhardwoodcuttings,whichoffersasimple,lowcostoptionforarangeofspecies.Sitesshouldbewelldrainedandshelteredfromstrong,coldwinds.Frostpockets should be avoided and the land free from perennialweeds.Lightersoilssuchassandy-loamsorsilt-loams are ideal, combining good natural drainage inwinterwithmoistureretentionpost-rootingin

summer.Shelteredsitesalsoenablethegroundto warmupquicklyinspringanddryoutsufficientlytoallowpromptliningoutofrootedcuttingsinspring; asouth-facingaspectisideal.Nodalcuttingsofwell-ripenedshootsarenormally used, around 20–25 cm in length and struck from Octoberonwards.Bushfruitsandrosespeciesforrootstocksusuallyhavetheirlowerbudsremovedtodiscouragegrowthfrombelowgroundlevel.Hormonerooting treatments are not usually required, although 0.8%IBAcanbeconsidered.Cuttings should be graded and only the thickest materialshouldbeusedinoutdoorsituations.Verythincuttingshavelowfoodreservesandmaydeterioratebeforerooting.Ifconditionsareunsuitableforliningout,cuttingscanbebundled,labelledandheeledin.Sharpsandorrecycledgrowingmediacanbeusedforheeling in and the cuttings inserted in trenches to about halftheirlength.Labelsshouldbeclearlyvisibleanddifferentspecieswellseparated.Some cuttings may begin to form callus tissue and initiaterootspriortoliningout,whichshouldbedonepromptlyinspringassoonassoilandweatherconditions are suitable, inserting the cuttings to about halftotwo-thirdsoftheirlength,15–20cmapartintherows.Cuttingsshouldbefirmedinwell.Onheavysoils,raisedbedsoffertheadvantageofimproveddrainage.With this system, the cuttings usually remain in situ until theautumn,whentheyareliftedforgrowingon,eitherinthefieldorincontainers.Duringthisperiod,goodweedcontrol and adequate summer irrigation are essential requirementstoproducequalityliners.

Heated binsThistechniquewasdevelopedatNIABEMRfortheimprovedrootingofleaflesswintercuttings(hardwoodcuttings)andissuitableforarangeofHNSsubjectsincluding Acer campestre, Acer platanoides ‘Crimson King’,Acer rubrum, Laburnum, Platanus x hispanica, Sorbus intermedia, Tilia, Ulmus glabra and various clonal rootstocks of Malus and Prunus.Timing, hormone preparation and base temperature are crucialtosuccess.The bins should be constructed in a cool, insulated building to maintain dormancy and restrict bud development.Theyneednotbeofanyfixedsizebutaretypicallysome1.2msquareand1mhigh,suchthattheycanaccommodatelengthycuttings.Abinofthissizewillholdaround5,000cuttings.Insulatingblocks are used for the construction to retain heat in the rootingareaandthepropagationmediummustbewelldrained for successful callusing and root initiation of thecuttings;floorblocksmust,therefore,havedrainagegapsbetweenthem.Once the blocks are in place, heating cables or a suitableheatfoilarelaidonthefloorofthebintoprovidethenecessarybaseheat;accurateheat controlusingreliabletemperatureprobesisessential.


Aweld-meshscreenisplacedoverthecablesforprotection.Finally,therootingmediumisplacedin thebin;mixesofpeatwithperliteorbarkworkwell.Usually, one-year vigorous healthy shoots are used for cuttings, ideally taken from clonal stock hedges or motherplants.Pencilthickshootsremovedcloseto thepreviousyear’swoodtoincludetheswollenshootbaseareideal.CuttingsrootmostreadilywhentakenduringOctoberandearlyNovemberinthecaseofplumrootstocks,ornamental Prunus and Tiliaspecies,andbetweenmid-FebruaryandMarch.Autumncuttingsmusthaveany foliage removed and those taken in spring should be collected before they come into leaf, so that the food reservesofthecuttingcanbechannelledintorooting.A ‘quick dip’ hormone treatment of IBA is normally used,exceptwherepreformedrootsarepresent,forexample,withthecherryrootstock‘Colt’,inwhichcaseitisunnecessary.Foruniformrooting,allcuttingsshouldbedippedtothesamedepthandforthesameduration.Theoptimumtemperatureforbaseheatisaround21°Cfortwoorthreeweeks.Allcuttingsshouldbeplacedatthesamedepthintheheatedbin,usuallyaround2.5cmabovetheheatsource.Thecuttingsshouldbecheckedregularlyforanywateringneedtoensuretherootingmediumisadequatelymoist.Once root initiation has occurred, the base temperature canbegraduallyreducedbeforebeingswitchedoffinreadinessforliningout.Theaerialenvironmentshouldremaincoolandwellventedtodiscourageshootsfrombreakingintoearlyleaf,asthiswillhinderrootdevelopmentandpost-plantingestablishment.

Heated bins are used to initiate callus and roots quickly

The cuttings can be lifted from the bin as soon as conditions are suitable for lining out or, if more convenient, they can be bagged and cold stored until required.Well-grownhardwoodcuttingsofrootstockscanbebuddedduringthesummerorgrownonfor a full season before being grafted or budded the followingyear.Good bin hygiene is important and the rooting medium shouldbechangedeachyear,otherwiseitsstructurewilldeteriorateanddrainagewillsufferanddiseaseinfectionmayensue.Binsshouldbedisinfectedbeforere-use.

Direct sticking of cuttingsDirectstickingmaybedefinedastheinsertionofan unrooted cutting or cuttings into an individual receptacle,whichmaybealinerpot,intermediatepot orfinalpot.Byblendingpinebarkwithdifferentgradesofpeat, towhichcontrolledreleasefertiliserisadded,arootingmediumwithasuitablyhighairfilledporosityforquickrooting can be obtained and good nutritional status achieved,servingasbotharootingandgrowingmediumfortheplants.

Advantages and disadvantages of direct stickingThe principal advantages of direct sticking are reduced root disturbance (leading to better plant establishment) andquicker,betterqualityplants.Disadvantagesincludethe greater inputs required at propagation, notably oflabour,space,materials(pots,media,etc.)andpropagationmaterial(whenmulti-sticking).When carried out correctly, direct sticking can save a lot oftimeandhandling.Itisnotanewtechniquebutimprovedmethodsofpropagation, notably the successful blending of pine barkwithpeatandcontrolledreleasefertiliser,enableittobeusedmorewidely,withscopeforsignificantreductionsinproductiontimesofeasyrootingsubjects.With this development, one of the main obstacles to successfuldirectstickingwasovercome,namelytheneed to begin feeding during and immediately afterrooting.Its success depends on:

• Using easy rooting subjects (greater than 75% take)

• Good,well-structuredrootingmediawith adequate nutrition

• Adequateavailablepropagationspacewhenrequired• Sufficientandtimelyquantitiesofuniform,good

quality cutting material

• Care in spacing plants to maintain quality

Research undertakenWorkatHRIEffordconsideredtheresponsesofarangeofHNSsubjectstodirectsticking,bothundermist (summer) and polythene covers (autumn and


winter),withaprincipalaimbeingtoestablishwhethera propagation mix containing higher levels of fertiliser couldbeusedwithoutadverselyaffectingrooting.Under both environments, the cutting quality and earlygrowthofdirectstuckmaterial(into7cmpots)werebetterthanthatoftrayrootedcuttings,wherecompetitionforavailablenutrientswasgreater.Overall,resultswerealsobetterina50:50peatand pine bark mix than a peat and grit one and cutting quality of both vigorous and some salt sensitive evergreenspeciesundermistimprovedwithincreasingfertiliserincorporation(upto2kg/m3 12–14 month controlledreleasefertiliser).Leafcolourwasimproved,stemthicknesswasgreater,andleaderandaxillarybudsweremoreactive,producingwell-rootedsmalllinersdirectfrompropagation.Noproblemswereencounteredwiththe2kg/m3 rate of fertiliser in the peat and bark mix but rooting of Camelliawasreducedwhereitwasusedinthepeatandgritmixes.Underpolythene,cuttingsdidlesswellinfertilisedpeat and grit mixes, particularly at the higher rate of fertiliser(2kg/m3).Whiletheinclusionofbarkimprovedrooting, the type and rate of controlled release fertiliser wassignificant,as,underthissystem,toohigharateof12–14monthfertiliser(2kg/m3)wasdamagingtosensitivespecies(Japanese Azalea);thesamerateofa16–18monthformulation(withaslowerpatternofnutrientrelease)provedsafer.Ultimately, the choice of controlled release fertiliser (particularlytherate)willdependupon:

• Whetherbarkisusedandtowhatextent

• Thelengthoftimecuttingsrequiretorootwell

• Whether or not base heat is used

• The rooting environment (polythene, mist or fog)

• Theseasonduringwhichpropagationtakesplace• The plant species concernedUsually,a12–14monthproductwillsuffice,although 16–18 month formulations are safer for salt sensitive subjects,especiallywherebaseheatisusedunderpolythene.1kglowerrates(1kg/m3) are usually requiredforautumnandwinterpropagation,particularlyunderpolytheneandwherebaseheatisused.WorkatHRIEffordconcludedthat,toobtainthemostbenefitfromthisapproachtopropagation,thetimingofsubsequentpottingonisimportant;theearlierthepottingofslowgrowingspeciesorthosewithdistinctgrowthflushes,thebetterbytheendoftheseason.Intrials, a delay in potting of the more vigorous subjects waslessdetrimentalastheirgrowthrateenabledthemtocatchupontheearlierpotting.The poor use of space resulting from cutting failures whendirectstickingcanbeoffsetbyusingmorecuttingsperpot.However,anadequatestockplantareais required, as are correct pruning schedules, to produce timelysuppliesofagreaternumberofuniformcuttings.

HNS subjects suitable for direct stickingSubjectspropagatedsuccessfullyatHRIEffordby multi-sticking cuttings into 7 cm pots included various ground cover subjects (including Hebe, Hedera and Hypericum), easy rooting amenity subjects (such as Forsythia, Senecio and Weigela), hedging species (Griselinea and Ligustrum), higher value subjects (evergreen Azalea, Camellia and Pittosporum) and even someslowerrootingandgrowingsubjects(Elaeagnus pungens‘Maculata’).Whilethreecuttingsperpotcan produce excellent results, for many easy rooting, vigorousspecies,twocuttingsusuallysuffice.Popular evergreens such as Hedera, Prunus tricolor and evergreen Prunus species can also be direct stuck into liners,1,2or3litrepotsandrootedwithoutheatunderpolythene during the late summer and autumn period, whileChoisya, Escallonia, Hypericum, Lavandula, Pyracantha and Potentilla can be direct stuck successfullyinto1or1.5-litrepotsduringthesummer.

AwiderangeofHNScanbepropagatedeconomicallybydirectsticking, including evergreen Prunus

Easy rooting deciduous subjects like Buddleia, Hypericum, Philadelphus, Potentilla and Weigela also rootwellwhendirectstuckinto1litrepotsinsummerundermistorshadedplastic.Buddleiawillinfactdirectstick successfully into 3-litre pots in summer to produce goodqualitysaleableplantsthefollowingspring,whilecultivars of Cornus alba also root readily but may require alittlelongertoproducesaleableplants.


Crop protectionThe high humidity environments created for seed germination and the rooting of cuttings also provide idealconditionsforpestsandparticularlydiseases.Notableexamplesinclude:Botrytis, Phytophthora, Pythium and Rhizoctonia, the latter three being commonlyassociatedwith‘damping-off’symptomsinseedlingsandcuttings.Pestssuchasaphidscanalsobequitecommononleafycuttings,whilesciaridflylarvae can feed and damage young roots and stembases.

Sciaridflylarvaedamageyoungrootsandstembases

Contaminatedstockplantsornurserycropsfromwhichpropagation material has been taken are a common source of problems, underlining the importance of disciplined nursery hygiene, routine pest and disease monitoringandcleanstock.Carefulwateringandenvironmental control are also important, particularly in respectofhumidityunderpolythene,mistandfog.As seedlings, cuttings and liners are usually quite soft andjuvenilewheninactivegrowththeyaresusceptibleto problems and more likely to sustain damage as a result of pesticide application, especially under mist orfog.There is also a diminishing range of suitable products approved for use under protection (although some of the newerbiopesticideshavepotential).Assuch,biologicalpestcontrolagentsdeployedwithinintegratedpestmanagement programmes are a safer, more sustainable andoftenmoreeffectiveformofpestcontrol.Recentmovestowardsintegratedcropmanagementseektobuild on this and bring together the use of biological controlagentswithgoodculturalpractice.Integrated pest management (IPM)IPM combines biological and cultural control measures forcropprotectionwiththeminimumuseofcompatiblepesticides.Usedcorrectly,itisasafer,moreeffectiveand environmentally responsible approach that reduces the use of and reliance on chemicals so helping to reducethedevelopmentofpesticideresistance.

Cultural measures include good nursery hygiene, use ofcleanstockandroutinecropmonitoring.AnincreasingnumberofHNSgrowers,includingpropagators,nowuseIPMunderprotectiontocontrola range of pest problems, including aphid, sciarid flylarvae,glasshousewhitefly,two-spottedspidermite,thripsandvineweevillarvae.Theseprotectedenvironmentslendthemselveswelltotheuseofbiologicalcontrolagents,which,whencoupledwithaccurate and regular pest monitoring, can be very effective.Reducedrelianceonbroadspectrumpesticides also enables more naturally occurring beneficialspeciestoestablish,someofwhichoverwinternaturallyunderprotectionormoveinsidefromoutdoorsinspringtoprovideadditionalcontrol.Forsuccessfulprogrammes,trainedstaffshouldmonitorcropsweeklyusingstickytraps,indicatorcropsandpheromonetrapsasappropriate.Agoodqualityx10magnificationhandlensshouldbeusedwhencheckingforpestsandbiologicalcontrolagents.The AHDB Horticulture HNS Crop Walkers’ Guide covers major pests, diseases, biological control agents(andbeneficials)andnutritional,culturalandphysiological disorders and is a useful source ofreference.Using IPM in propagation situationsBiologicalpestcontroliswellsuitedtopropagationandlinerproduction,whereleafcanopiesfrequentlytouch,so facilitating the rapid spread and establishment of predators, normally introduced in a bran or vermiculite carrierfromareleasetub.However,thehighertemperature and closer humidity environments of propagation units, may restrict the range of biological pest control agents and release methods that can beused.The predatory mite Phytoseiulus persimilis commonly usedtocontroltwo-spottedspidermiteislesseffectiveathighertemperatures(above25°C)andsoadifferent,more temperature tolerant predatory mite, Neoseiulus (Amblyseius) californicus, may be more suitable in propagationpurposes.Slowreleasesachetsusedfortheintroductionofsome biological control agents (such as Amblyseius andersonifortwo-spottedspidermitecontrol)areunsuitableforuseindamppropagationenvironments.Extra care is also required to ensure release bottles of parasiticwaspsplacedinpropagationareasarenotleftupright,wheretheycanfillwithwaterandsodrownthebiologicalcontrolagentsinside.A further consideration in propagation areas is theusuallyrapidthroughputofcrops,whichwillnecessitate more frequent introductions of biological controlagents.Stickytrapsusedtomonitorflyingpestssuchaswhitefliesandsciaridfliesmayalsorequiremorefrequentchangingwhenusedinpropagationenvironmentsduetothehighernumberoffliesoftenassociatedwithhighertemperaturesandveryclose,humidenvironments.

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96 Aftercare

Integrated crop managementIntegrated crop management is a sustainable approach togrowing,whichbuildsonandincludesIPM.Ineffect,it is a broader concept that brings together the correct identificationofcropproblemsthroughmonitoringandstafftraining,withculturalcontrolmeasures(nurseryhygiene,carefulwatermanagementandaccurateenvironmental control), biological control products, biopesticides and the use of compatible pesticides tocontrolpests,diseasesandweeds.Likeintegratedpestmanagement,whenundertakencorrectly, integrated crop management combines high levelsofsustainablecropprotectionwithenhancedplantquality,mitigatingpesticideresistanceissueswhileprovidingahighdegreeofcropsafety.Itisalsomoresocially acceptable than the repeated use of synthetic pesticides, particularly the use of broad spectrum, persistentproducts.AHDBHorticultureprojectHNS185:Understanding and managing crop protection through integrated crop management, aimed to assess and quantify the present level of adoption of the management technique innurserystock.Theresultswillenablebetterpracticemethodstobeidentifiedanddeveloped,whichareeconomicallyviable,practicalforgrowerstoimplementand take account of ongoing changes in crop protection legislation, notably the EC Sustainable Use Directive (SUD),whichrequiresgrowerstoreducetheuseofpesticidesanddemonstrategoodpracticeby2014.Biopesticides and compost teasBiopesticideslinkwellwiththebroaderconceptof integrated crop management and are based on beneficialmicroorganismsorotherbiologicallybasedactiveingredients.Current commercial products include Serenade ASO (based on the bacterium Bacillus subtilis), Prestop (based on the fungus Gliocladium catenulatum), T-34 (based on the fungus Trichoderma asperellum T-34) all withactivityagainstdiseasesandMet-52(basedontheentomogenous fungus Metarhizium anisopliae), used for protectionagainstvineweevil.OtherexamplesincludeNaturalis-L,developedusingtheentomopathogenicfungus Beauveria bassiana for the control of leaf pests (notably,aphidsandwhitefly)andDipelDF,abacterialinsecticide based on Bacillus thuringiensis a naturally occurringbacterialpathogenofcaterpillars.There is continuing interest in the potential of compost teastostimulatehealthycropgrowthandreducetheincidence and severity of diseases such as Botrytis, downymildew,leafspotsandvarioussoilandwater-borneinfections.Theirbeneficialeffectdependsonthelive microorganisms they contain acting as biological controlagents.Giventheyarealsosafetocropsandare user-friendly, their appeal is understandable yet commercial experience has been variable in terms of diseasecontrol.AHDBHorticultureprojectHNS125:Hardy Ornamentals: the potential of compost teas for

improving crop health and growth, sought to evaluate thepreparation,applicationandeffectsofcompostteasonUKcommercialnurseriesandprovidegrowerswithpracticalinformationtoimprovetheiruse.Overall,theresultswerevariableandinconclusive.However,wherecompostteashavebeensuccessfullyintegratedwithincommercialcropmanagementprogrammes,significantcost savings have accrued due to more limited use of fungicidesandfertilisers.Basedonpresentknowledge,compostteasarelikelytobemosteffectivewhenusedaspartofawider,integratedcropmanagementapproach.Growersdo,though,needtoexperiment,refineandadaptcompostteastotheirownsituationandrangeofcrops.Other productsAswellasbiopesticidesandmicro-feedingwithcompostteas, other products are available commercially that claim toimproveplantresistancetopestsanddiseases.Theyare usually based on nutritional elements, micronutrients, repellents,beneficialmicrobesorplantextractsandarethought to improve plant resistance by either creating a microbialbalanceinfavourofbeneficialmicroorganisms,whichactasdiseaseantagonists,inhibitingtheformationand germination of disease spores or by acting as a plant wash,feedsupplement,plant‘enhancer’or‘tonic’.Notalloftheseproductshavebeenofficiallyregisteredand,therefore,theirusecannotberecommended.

Pest and disease controlCommon pest problems in propagationAphidsSeveral aphid species are common on protected ornamentals including propagation and liner crops, most notably peach-potato aphid (Myzus persicae), potato aphid (Macrosiphum euphorbiae), melon and cotton aphid (Aphis gossypii) and glasshouse and potato aphid (Aulacorthum solani).Theyfeedonanddamageawiderangeofsubjects,causingleafyellowinganddistortion,producingstickyhoneydewthatleadstothedevelopmentofsootymould.Aphidsareeasilytransferred on tip cuttings and soft, sappy propagation material.Theymayalsoactasvirusvectorsandinfectedmaterialshouldnotbeusedforpropagation.Variousbiologicalcontrolagentsarenowavailableforsafeandeffectivecontrol,mainlyparasiticwaspssuch as Aphidius colemani and A. ervi. Products are also available that combine several species of parasiticwaspsinonetube,makingcontrolofmixedaphidspecieseasierandmorereliable.Thepredatorymidge, Aphidoletes aphidimyzaandthegreenlacewingChrysoperla carneaareusefulsupplementstodealwithaphid‘hot-spots’.Sciarid and shore fliesSciaridflylarvae(Bradysia difformis) are a common pest ofHNSseedlingsandcuttings,especiallyslowrootingspecies,feedinginandaroundthegrowingmediaonfungi,youngrootsandstembases.Theythriveindamp,humid conditions, hence their occurrence on

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Case study 6: Walberton Nursery An integrated approach to crop protectionSussex-basedWalbertonNurserygrowsaroundonemillion shrubs and herbaceous perennials each year forsalein1,2and3-litrepotstogardencentres.Around half of these are propagated in-house and the remainder bought in as rooted plugs or pot liners.Lowpolythenetunnels(cladwithXLThermo-propfilm)overaheatedconcretefloor(minimum20°C)areusedtorootandweanawiderangeofcuttings,including Crinodendron, Erysimum, Lavandula, Penstemon, Photinia and Spiraea. “We place a strong emphasis on managing the propagationenvironmentwell,particularlyhumiditylevels throughout the rooting process,” explains TechnicalManagerDavidHide.“Toincreaselevels,wemayplacetraysontocapillarymattingandthencoverwithpolytheneand,insomeinstancesaswebegintowean,wemayplacefleeceunderneaththepolythenecoverpriortoremovingit.“We also vary the environment according to the subjectsinvolved,forexample,weliketokeepLavanduladrierwhileSpiraeapreferawetterregime,”saysDavid.“Weventquitefreelytooduringhotweather,sothecuttingsremainrelativelycool.“We propagate cuttings throughout the year and, for the most part, use milky polythene covers overthetunnelsbutpreferaclearfilminwintersothecuttingsreceiveasmuchlightaspossible.Ventilation, heating and shade screens in the glasshouseareallcontrolledautomatically.“We are also keen on good hygiene and diligent cropprotection,”continuesDavid.“Wehavearoutinefungicideprogramme,whichincludesthebiopesticide Serenade ASO to control Botrytis, whichisourprincipalconcern,especiallywithmicropropagatedmaterial.Wealsoliketocropwalkweeklytocheckpestlevels.Stockplantand propagation check-sheets are used too, for monitoring the quality, and pest and disease statusofallcuttingmaterial,includingthatwhichisboughtin;wefeelthishelpsdriveupthequalityof material coming into the propagation unit and wehavedevelopedbenchmarksaspartofawiderappraisalsystem.“Weremovenurserywastepromptly,disinfectfloorareas, use only fresh propagation media and change thepropagationfilmsregularly.Theconditionofthecuttings in the trays is also checked regularly so that anything that’s damaged or diseased can be spotted anddealtwithpromptlybeforeitbecomesa biggerproblem.“Weliketousebiologicalpestcontrolwherewecan and use the predatory rove beetle Atheta

(viabreederboxes)forsciaridflycontrolandthepredatory mite Neoseiulus (Amblyseius) cucumeris forthripscontrol(plugsare‘loadedup’withpredators before moving them onto the nursery) as wefeelthesearemuchmoreeffectiveandsafertocrops,especiallycuttings,thaninsecticides.“We may also look at Amblyseius andersoni, Neoseiulus (Amblyseius) californicus and Phytoseiulus persimilisfortwo-spottedspidermitecontrol,forthesamereasons;ifusedcorrectly,theyareusuallymoreeffectiveandagooddealsaferthan chemical control, especially in propagation situations.WealsomakefortnightlyapplicationsofthebiopesticideNaturalis-Lduringthesummerforgeneralcontrolofleafpests.”

Neoseiulus (Amblyseius) cucumeris

The nursery is geared to integrated crop management and uses biological pest control to goodeffect.“We’vefoundthedevelopmentworkonAtheta breeding programmes very useful as sciarid can be a particular problem in propagation and the predatorsgiveuseffectivecontrol.Thefollow-onAHDBHorticulturefactsheet06/10isespeciallyusefultousaswemakegooduseofbreederboxesinthepropagationunit.WemayalsolookatAtheta andthepredatoryflowerbugOrius as a supplement to Amblyseius predators for thrips control under protection,”saysDavid.Thenurseryhasalsoexperimentedwithcompostteaasanaidtoimprovingcrophealthandgrowthin propagation and liner crops but didn’t see anynoticeabledifferencesbetweentreatedanduntreatedcrops,sodiscontinuedit.“Wewereconverts to compost tea,” says David, “but stopped whenwecouldn’tseewhatwewereachieving.Weapplied compost tea to a number of batches of plants and left similar sized batches untreated and couldnotseeanydifferenceandsogaveuponalltheadditionalwork”,heconcludes.

98 Aftercare

Sciaridflylarva

Sciaridfliesareoftenmistakenforshoreflies(Scatella tenuicosta) but the latter are larger, stouter and more fly-like.Likesciaridflyadults,shoreflyadultsdonotharm plants but feed on algae, hence, they can be presentinlargenumberswhereexcessmoisturehasenabledalgaetodevelop.Assuch,propagationareasare ideal breeding grounds and their large-scale presence canalsobeanuisancetonurserystaff.Theyareoften seen sitting on plant foliage or the surface of the propagationmediumandflyupwardswhendisturbed.

Sciaridflyadult

crops in propagation and can create serious damage ifnotcontrolled.Thelarvaearearound5–8mmlong,off-whiteincolourwithablackheadandnolegs.Themostfrequentsignofattackiswilting,poorgrowthandcollapseofaffectedplantmaterial.The adults are small (3–4 mm long) grey-black gnat-like flieswithlonglegsandantennae.Theyarecommonlyseeneitherwalkingorhoveringoverthesurfaceofthegrowingmedium,particularlywhenitisdamporoverlywet.Theydonotfeedonplantsbutcanactasvectorsof disease pathogens, notably Pythium.Theirpresencein large numbers can also pose a nuisance to nursery staffworkingnearby.

Both pests can be reduced by good nursery hygiene andavoidingexcessivemoisture.Promptremovalofplantdebrisandtheuseofyellowstickytrapsformonitoringwillalsoreducenumbers.While a number of products are currently available for the chemical control of both pests (adults and larvae), amoreeffectiveandsustainableapproachforsciaridcontrolistousebiologicalcontrol,forwhichspeciesofthe predatory mites Hypoaspis and Macrocheles and the predatory rove beetle Atheta coriariaareavailable.

The predatory mite Hypoaspiscanprovideeffectivecontrolofsciaridflylarvae

Atheta coriaria can be used against both sciarid and shorefliesandmaycontributetothebiologicalcontrolofthegrounddwellingstagesofwesternflowerthripstoo.Theblackadultbeetlesarequitelarge(around 5mmlong)andflyreadily;bothadultsandlarvaearevoraciouspredators.Thispredatorappearstosurvivebetter than Hypoaspis in high moisture situations and so may be more suitable for use in propagation unitenvironments.Most recently, commercial success has been achieved using ‘breeder boxes’ for Atheta. Theseweredevelopedthrough AHDB Horticulture projects PC 239 and PC 239a: Protected herbs, ornamentals and celery: Development of an on-nursery rearing system for Atheta coriaria for reduced cost biological control of sciarid and shore flies, and are simple polystyrene boxeswithholesdrilledinthesidesandtop,containingmoistpeatandafoodsource.WhenAtheta is released intotheboxes,theybreedrapidlyandflyouttocoloniseotherareas.

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The predatory rove beetle Atheta coriaria can also be used for safeandeffectivecontrolofsciaridflylarvae

AHDBHorticulturefactsheet06/10:Grower system for rearing the predatory beetle Atheta coriaria, provides more detailed guidance on the use of breeder boxes for reduced cost biological control of sciarid and shoreflies.Both Atheta and Hypoaspis require a minimum temperatureof12–15°Ctobeeffectiveandso shouldnotbeusedinunheatedcropsoverwinter.Biologicalcontrolofsciaridflylarvaecanalsobeachieved using the insect pathogenic nematode Steinernema feltiaeappliedasagrowingmediadrench.Usually,aminimumtemperatureof10–14°Cisrequiredforeffectivecontrol,dependingontheproduct.AHDBHorticulturefactsheet08/02:Control of sciarid flies in protected ornamentals, provides more advice ondealingwithsciaridfliesunderprotection.Slugs and snailsSlugs and snails favour damp, humid conditions and can create serious damage among young seedlings and cuttings, holing out and quickly shredding young foliage andconsuminggrowingpoints.Inrecentyears,thewatersnailspeciesOxyloma pfeifferi(small,palebrownor black in colour up to 12 mm long) has become very common in nursery stock, feeding on a range of plants, algaeanddecayingvegetation.Choisya, Cordyline and Phormium appearespeciallyvulnerabletoattack.

Several slug species can be found in protected ornamentals, the most common being Deroceras panormitanum,whichisbrownish-greyandupto35mmlong.ManyHNSsubjectsarefrequently attacked including Choisya, Clematis, Cordyline, Magnolia, Phormium and various herbaceous perennials, notably Hosta and Ligularia.Damage isveryvisibleandcanoccurquicklywhennumbersbuildup;seedlings,cuttings,linersandoverwinteredherbaceouscropscanbeespeciallyvulnerable.

Watersnailsfavourwarm,dampconditionsandareacommonproblem in propagation crops

Cultural control measures are the key to successful controlofbothpests,includingcarefulwaterandenvironmentalmanagementtoavoidoverlywetconditions, good bed drainage and rigorous nursery hygienetoreducetheirnumbers.AHDBHorticultureprojectHNS105/105b:Integrated control of snails and slugs, highlighted the potential of permeable ground cover fabrics impregnated withalatex-basedcopperhydroxidetreatmentfordiscouraging slugs and snails and these may be useful for propagation beds, as they also help to control rootingthrough.Biologicalcontrolusingthemolluscpathogenic nematode Phasmarhabditis hermaphrodita (availablecommerciallyas‘Nemaslug’)canalsoprovidesomecontrolduringthespringandautumnmonths.AHDBHorticulturefactsheet07/02:Integrated control of snails and slugs and AHDB factsheet: Integrated slug control,providesamoredetailedoverviewofcontrolmeasuresforbothpests.ThripsThey are an increasingly common and serious leaf pest of protected nursery stock, including propagation and linercrops,wherefeedingdamagecausesanunsightlyanddamagingwhitefleckingandgrowthdistortion.ThemainspeciescausingdamageonHNSisthewesternflowerthrips,whichcanalsotransmitdamagingvirusestoornamentalcrops.Commonhostcropsinclude:Campsis, Chaenomeles, Choisya, Clematis, Lavatera, Passiflora, Photinia and various herbaceous crops, including Cosmos and Crocosmia.

100 Aftercare

Westernflowerthripslarvaeandadults,acommonandseriouspestofanincreasinglywiderangeofHNS

Routine monitoring using indicator crops and blue sticky trapsenablerapiddetectionandpromptcontrol.Chemicalcontrolisdifficultandcomplicatedbywidespreadresistanceamongthripspopulations. As such, biological control using the predatory mites Neoseiulus (Amblyseius) cucumeris and, more recently, Amblyseius swirskii or Amblyseius montdorensis has become the principal means of control under protection andthemosteffectivewhenusedcorrectly.Thesemites can be used in propagation areas and among linercrops.GrounddwellingHypoaspis and Atheta predators,usedforsciaridflylarvaecontrol,alsofeedonthripslarvaeandpupaeinthegrowingmediumor onfloororbenchcoveringsandsoareausefulsupplement to Amblyseius.ThepredatoryflowerbugOrius is also a useful supplement to Amblysieusmites;itisveryactiveandfeedsonarangeofpreyincludingthripsbuttendstoflyelsewhereiffoodsourcesarescarce.AHDBHorticulturefactsheet14/09:Thrips control on protected ornamental crops, provides more detailed guidanceondealingwiththrips.Two-spotted spider miteThisisafrequentandtroublesomeleafpestofawiderangeofHNSsubjects,notablyBuddleia, Ceanothus, Choisya, Cordyline, Crinodendron, Euonymus, Exochorda, Hydrangea, Magnolia, Phormium, Potentilla, Skimmia, Wisteria and various alpines, herbaceous perennialsandgrasses.Whiledislikinghumidityandso less frequent in propagation environments, it does favour higher temperatures and is commonly found on container-grownstockplants,weanedmaterial,rooted plugsandlinersgrownonunderprotection.Damagesymptoms,typicallyinclude,ayellowingandbronzing of the foliage, leaf speckling and a gradual loss of plant vigour.Withheavyinfestations,webbingquicklyoccurs,makingplantsunsaleable.

Two-spottedspidermiteisafrequentleafpestofHNS

Chemicalcontrolsarewidelyusedbutresistanceiswidespreadleadingtovariablelevelsofcontrol.Inpropagation situations, spray scorch of soft, young growthisafurtherconsideration.Biologicalcontrolagentsarenowwidelyusedforsuccessfulcontrol,mainly the predatory mite Phytoseiulus persimilis although this has some limitations, mainly its dislike oftemperaturesover25°C,sensitivitytopesticideresiduesandrelianceontwo-spottedspidermiteasafoodsource.Forthesereasons,thereisnowmoreuseof other predators, usually to complement Phytoseiulus rather than replace it, notably Neoseiulus (Amblyseius) californicus and Amblysieus andersoni,bothofwhicharemoretolerantofhigherandlowertemperaturesandcan survive on other food sources in the absence oftwo-spottedspidermites.LarvaeofthemidgeFeltiella acarisugacanalsobeaneffectivepredator oftwo-spottedspidermites.Currently, use of Neoseiulus (Amblyseius) californicus is only permitted in glasshouses and fully enclosed polythenetunnels;theintroductionrateisalsogovernedbyitsreleaselicense.ThenativespeciesA. andersoni canbeusedwithoutsuchrestrictionsonoutdoornursery stock, so it may have a useful role to play in stockplantareasduringthespringandsummerperiod.AHDBHorticulturefactsheets08/05:The biology and control of two-spotted spider mite in nursery stock, and12/09:Biology and control of mites in pot and bedding plants,providefurtherguidance.Vine weevilTheblackvineweevil(Otiorhynchus sulcatus) is one ofthemostdamaginganddifficulttocontrolpestsof nursery stock, including rooted cuttings and pot liners,fromwhereitcanreadilytransfertolarger,saleablestockwhenpottedon.Thewideruseofpeatalternatives,notablycoirfibre,barkandwood-fibrealsoappearstofavourvineweevil,underliningtheneedforeffectivecropprotection.KeyhostsincludeAzalea, Cornus, Cotoneaster, Fuchsia, Euonymus, Parthenocissus, Pyracantha, Rhododendron, Taxus and Viburnum.Variousalpinesandherbaceousperennials are also susceptible, notably, Astilbe, Bergenia, Epimedium, Heuchera, Hosta, Primula, Saxifrage and Sedum.

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Theadultisalargeblackweevilwithsmallyellow-brownpatchesonitsback.Itcannotflybutisanactiveclimber.Usually,ithidesduringthedayamongplantdebris, leaf litter or under pots and trays and feeds at night,causinganunsightlymarginalleafnotching.ThecreamywhitelarvaewithbrownheadsusuallyhatchandfeedontherootsystemsofplantsbetweenJulyandthefollowingspring,damagingbulbsandcorms,rootsystems,andstembases,leadingtostuntedgrowth,wiltingandcollapseofplants.LarvaepupateinthegrowingmediuminlatespringandnewadultsnormallyemergefromMayonwards,althoughthismaybeearlierunderprotection.

Vineweevillarvaecanseriouslydamagerootedcuttings,plugplants and liners

Theculturalcontrolmeasuresusedagainstvineweevilare especially important, notably good nursery hygiene andcleanstock.Checkbought-inplugsandlinersasa matter of routine and isolate these from other nursery cropsuntilchecked.In propagation situations, biological control using insect pathogenic nematodes are crop safe and especiallyuseful;usedcorrectly,theycanprovideeffectivecontrolofyoungvineweevillarvae.Most recently, research (AHDB Horticulture project HNS133:Development of the entomogenous fungus Metarhizium anisopliae for control of vine weevil and thrips in horticultural growing media), highlighted the potential of the entomogenous fungus Metarhizium anisopliae for biological control of the larvaeingrowingmedia,particularlywhenusedalongside cold tolerant entomopathogenic nematode products.Ithassincebeendevelopedcommercially,as a granular biopesticide product (Met-52) for incorporationintogrowingmediaatallproductionstagesincludingpropagation.

AHDBHorticulturefactsheet24/16:Vine weevil control in hardy nursery stock provides further guidance on vineweevilcontrolandtherangeofsusceptibleplanthostspecies.WhitefliesBoththeglasshousewhitefly(Trialeurodes vaporariorum)andthenotifiabletobaccowhitefly(Bemisia tabaci) are common leaf pests of protected crops and can easily transfer to propagation environments on contaminated cuttings, including bought-in plant material, so vigilance and routine qualitycontrolchecksareimportant.Leafdiscolorationdue to feeding activity is a common symptom but heavilyinfestedplantsbecomestickywithhoneydewandunsightlywithsootymoulds.Keyhostcropsinclude: Abutilon, Arbutus, Campsis, Ceanothus, Clematis, Cotinus, Hebe, Jasminum, Lavatera, Lonicera, Melianthus, Penstemon, Philadelphus and Viburnum.

Whitefliescancauseseriousleafdamageonarangeofcrops

Yellowstickytraps,checkedweeklyandchangedmonthlyareanessentialaidtowhiteflymonitoring.TheparasiticwaspEncarsia formosaisawidelyusedandeffectivebiologicalcontrolagentwhencorrectlyused(althoughitismoreeffectiveagainstglasshousewhitefly).Eretmocerus eremicus is another parasitic waspthatcanbeconsideredandisactiveagainstbothglasshouseandtobaccowhitefly.Italsoappearstotolerate higher temperatures and is more resistant to pesticide residues than Encarsia.ThepredatoryladybirdDelphastus catalinae is a useful supplement too, for controllingwhitefly‘hotspots’(althoughitshouldonlybeusedwhentemperaturesare21°Corhigherwithgoodnaturallightlevels).

Common disease problems in propagationBotrytisBotrytis or ‘grey mould’ is a common problem in propagation and liner situations, favoured by damp, high humidity environments and exacerbated by senescing anddecayingplanttissue.Cleanpropagationmaterialand good cultural practice is therefore crucial in avoiding andcontrollingthisdisease,whichoftenbeginsasasecondary infection colonising dead material before

102 Aftercare

spreadingtohealthyfoliageasaprimarydisease.Thediseaseleadstocharacteristicpalebrowntissuedecayandfluffyfungalstrandsbearinggrey-brown sporeclusters.

Botrytis is favoured by high humidity propagation environments

Propagation material should be checked daily and picked over promptly to remove any decaying plant material.AHDBHorticulturefactsheets23/02:Control of grey mould (Botrytis cinerea) in container-grown ornamentals: unheated greenhouse crops, 24/02:Control of grey mould in container-grown ornamentals: heated glasshouse cropsand25/02:Controlling humidity to minimise the incidence of grey mould (Botrytis cinerea) in container-grown ornamentals: heated glasshouse crops, provide further guidanceondealingwithBotrytisinprotectedcrops.Damping-offDamping-offrequiresthesamediligentapproachtonurseryhygieneandcrophusbandryaswhendealingwithBotrytis.Cleantrays,gooddrainageofbedsandpropagation media and periodic disinfection of materials are especially important, linked as the disease often is to the fungal pathogens Pythium and Phytophthora, whichfavourdampconditionsandhighmoisturelevels.Rhizoctoniainfectionalsocreatesdamping-offsymptomsbutismoreusuallyassociatedwithdrierenvironments.Fungicidesareavailabletoprotectagainstdamping-off,usuallyappliedasgrowingmediadrenchtreatmentsfollowingseedsowingorinsertionofcuttingsbutsuchproductsneedtobeharnessedwithgoodculturalpracticeforeffective,lastingcontrol.Thereisalsointerestinthewideruseofvariousmicrobial products to aid control, either incorporated intothegrowingmediumor,appliedasdrenchtreatments, as protectants, although commercial

experiencetodateappearsvariableandfurtherwork isrequiredtofullyevaluatetheirrole.AHDBHorticulturefactsheets16/04:Control of Phytophthora, Pythium and Rhizoctonia in container-grown hardy ornamentalsand17/04: Control of Pythium, Phytophthora and Rhizoctonia in pot and bedding plants, provide more detailed guidanceonthecontrolofdamping-offdiseasepathogens.

Weed controlWeed control in container-grown protected cropsWeed contamination from stock plants including seed oncuttingmaterialorrootfragmentsofperennialweedsonfield-grownherbaceousstock,canbeproblematic.Chemicalweedcontrolisoftendifficultinpropagationand protected environments due to the enhanced risk of damage because of the greater softness and sensitivity of the plant material and the lack of suitable herbicide products that are safe and approved for use in such situations.Weanedcuttingsandpotlinerswithshallow,limited root systems are also more susceptible to residualherbicidedamageorgrowthsuppression.Nursery hygieneGiven the complications of chemical control under protection, good nursery hygiene is particularly importantandshouldformthecornerstoneofallweedcontrolstrategies.Principalweedsourcesincludenon-cropareassuchaspathways,bededgesandareasbetweentunnelsandglasshousesaswellasrubbishheaps,uncoveredwasteskips,usedpotsandold,unsoldstock.

Goodnurseryhygieneiscrucialforsafeandeffective weedcontrol

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Routinenurseryhygienemeasurestominimiseweedcontamination should include:

• Coveringwasteheaps• Coveringgrowingmediastorageareasandwater

storage tanks

• Controllingbackgroundweeds(onpaths,headlandsand reservoir banks)

• Using clean pots and trays

• Disinfection of beds and benches and regular changing of bed covering materials and capillary matting before they become too soiled

• Monitoringcropsregularlyandhandweedingpromptly

AHDBHorticulturefactsheets03/14:Use of chemical disinfectants in protected ornamentals production and10/07:Guidelines on nursery hygiene for outdoor and protected ornamental crops, provide moredetailedguidance.Cultural control measuresCulturalweedcontrolcombinesgoodnurseryhygienewithdiligentcrophusbandry,notablythemanagementofwater,cropnutritionandthecropenvironment.Inpropagationandlinersituations,carefulwatermanagementtominimiseweedssuchasmossandliverwortisespeciallyimportant.Otherculturalcontrolmeasures of particular relevance to propagation and protected crops include:

• Ensuringweedsarewell-controlledinstock plant areas

• Onlytakingcuttingsfromclean,weed-free nursery crops

• Ensuring bought-in cutting material, modular raisedplantsandlinersarecleanandweed-free

• Rigorouscontrolofweedsinandaround propagationbedsandpathways

• Well-targetedhandweedingtoensurepromptremovalofweedsinpropagationareasbefore theyflower

• Promptandcarefulremovalofweeds,includingmossandliverwortfrommoduleswhenpottingon.

Guidance on the practical aspects of handling bought-in plant material can be found in AHDB Horticulture factsheet06/08:A guide to best practice when handling bought-in plants.AHDBHorticultureprojectHNS93:Nursery stock propagation: moss, liverwort and slime control, consideredweedcontrolinrootedplugsandpotlinersunderprotection,giventhatmossandliverwortinparticularareseriousproblemswhenholdingbackrooted plugs pre-potting and during young plant developmentfollowinglinerpotting.Withplugsinparticular,difficultiesinachievinguniformityofwateringand the presence of empty cells from cutting failure, acceleratesthecolonisationofgrowingmediasurfacesbymossandliverwort.Thesearedifficulttocompletely

handweedbeforepotting;somedebrisandinoculuminevitablytransfertotheliner,wheretheyquickly re-establish,especiallywithoverheadirrigationand inoverwinteredcrops.TheprincipalfindingofHNS93and,subsequently,ofHNS93c:Protected container-grown nursery stock: chemical and non-chemical screening for moss and liverwort control in liners,wasthattheadoptionandmanagementofdrierwateringregimesoruseofreducedpeatgrowingmediamarkedlyreducedmossandliverwortproblemsandwasaneffectivemeansofculturalcontrol.Mulches, pot-toppers, tray mats and bed covering materialsLoose-fillmulches,pot-toppersandpermeablebedcovers all help to exclude light and reduce surface moisture,sohelpingtocontrolweeds.Mulchesarecapableofprovidinggoodlevelsofsafeweedcontrolinshort-termcontainer-grownplantsandareausefuloptionforherbicidesensitivecropssuchasweanedcuttingsandstockplants.Theyareespeciallyeffectiveatcombatingmossandliverwort.Variousbark-toppingmachinesarenowavailablecommerciallytoapplymulchesandsoeaseandspeedtheirapplication.

Loose-fillmulchessuchasbarkofferasafealternativetochemicalweedcontrol

InHNS93c,pinebarkappliedtoadepthof10mmwaspartiallyeffectiveasamulch,delayingtheonsetofmossandliverwortgrowth.Thisapproachisnowmorewidelyused,combiningasitdoessafeandreasonablyeffectivecontroloftheseweedswithanattractivevisualappearance.Pot-toppers are permeable discs or mats that are placedoverthesurfaceofthegrowingmediumtocontrolweeds.Theyareusuallyappliedonce,after

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potting,and,forbestresultstoaclean,weed-freesurface.Inpropagationsituations,theyareausefuloptionforsafeandeffectiveweedcontrolandcanbeconsidered for pot liners although their application to smallpotsistime-consumingand,hence,quitecostly.Severalproductsarenowcommerciallyavailabletofitarangeofpotsizes,includingthosemadefromsustainablesourcessuchashemp.AfurtherandmorerecentdevelopmentfromtheNetherlandsistheuseofpermeabletraymats,whichactasamulchtocontrolweedsinplugstransplantedintotraysunderprotection.

Permeabletraymatscontrolweedssafelyintransplantedplugs

Growing media amendmentsCommercial experience and research indicates that weedssuchasmoss,liverwortandpearlwortarelessofaproblemwherebarkandwood-fibreareusedinthegrowingmediumandthepercentageofpeatisreducedto50%byvolume.HNS93calsoconsideredthepotentialroleofgrowingmedia amendments to reduce industry reliance on chemicalsforreducingmossandliverwortproblemsinlinersalongsidearangeofherbicideprogrammes.Theincorporationof30%wood-fibreinapeat-basedmediumsubstantiallyreducedmossandliverwortincidencemakingchemicalcontrolmucheasier.

Inmorerecentwork(AHDBHorticultureprojectsHNS126: Biology, epidemiology and control of liverwort infestation in nursery plant containers,andHNS175:Liverwort control using novel techniques), various oilseed meals including Limnanthes alba, Sinapis albaandoilseedrape(eachofwhichcontainvariousglucosinolatesthatbreakdowntoformbioactivesecondaryproducts)havebeenshowntoprovidesomecontrolofliverwortwhenusedasamulch.With good nursery practice and non-chemical alternatives, there should be no need to use or consider herbicidesinorneartopropagationenvironments.AHDBHorticulturefactsheet25/12:Non-chemical weed control for container-grown nursery stock, provides further, more detailed guidance on cultural andothernon-chemicalweedcontrolmeasures.Herbicide optionsCurrently, there is only a single residual herbicide product,Flexidor500(isoxaben),whichisapprovedforuseonnurserystockgrownunderprotectedstructuresand can be considered to give pre-emergence control of arangeofweedsinrootedcuttingsandpotliners.Flexidor500hasalabelapprovalpermittinguseonHNSunderprotection.However,severalHNSsubjectsaresensitive to it and may be especially vulnerable in plug trays,wheretherootingvolumeismorerestrictedandrootsofcuttingsareoftennearthesurface.A number of AHDB Horticulture screening trials have beencarriedoutwiththisherbicideproducttoprovidebetterinformationonitsefficacyandcropsafetywhenusedonHNSunderprotection,includingweanedcuttingsinplugtraysandpotliners.InearlyworkwithpotlinersatHRIEfford(AHDBHorticultureprojectHNS35b:Herbicide screening under protection), LavandulasufferedaslightchecktogrowthwithFlexidor125.Furtherworkcontinuedwithlinersandweanedcuttingsinplugtraysunderprotection(HNS35g: Chemical weed control in container-grown nursery stock under protection),withawiderrangeof species and treatments, including Flexidor 125 at the reducedrateof1litre/ha.InHNS35g,somespeciessufferedreducedordelayedspringgrowthfromsummerapplicationsofFlexidor125(thiswasmoreofaproblemwithplugtrays,wheretherootingvolumeismorerestrictedthanwithliners).Buddleia and Lavatera weredamagedbytreatmentsinvolving Flexidor 125, and Clematis also appeared sensitive,withreducedspringgrowthandevenplantdeath.Thereweresomeindicationsthatearlywinterapplicationsweresafertosensitivespecies.Table20(overleaf)providesfurtherguidance.Intermsoftheweedspectrumcontrolled,Flexidor500hasweaknessesnotably,groundselandwillowherb.Theproducttoocannotberelieduponforeffectiveandsustainedcontrolofliverwortandmoss.Asaresultofthelimitednumberofapplicationswhichcanbemadepercrop,culturalmethodsofweedcontrolshouldplayanimportantroleinanyweedcontrolprogramme.

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Table20.ToleranceofprotectedHNSlinersandweanedcuttingsin plug trays to Flexidor 500

Herbicide Flexidor 500

Approval status Label approval

Berberis

Buddleia

Ceanothus

Chaenomeles

Choisya

Cistus

Clematis

Cornus

Cotoneaster

Cytissus

Escallonia

Euonymus *

Forsythia

Hebe

Hedera

Hypericum

Jasminum **

Kerria

Lavandula

Lavatera

Ligustrum

Lonicera

Osmanthus

Parthenocissus

Polygonum

Potentilla

Pyracantha

Rosmarinus

Santolina

Senecio

Spiraea

Viburnum

Vinca

Weigela

Susceptible: Unacceptable crop damage normally occurs – do not treat

Moderately susceptible: Some crop damage may occur but plants normallygrowaway

Tolerant: Crop damage does not normally occur

Notes:Onlyalimitednumberofspeciesandcultivarsweretestedwithineachgenus,itis,therefore,essentialtocarryoutsmall-scaletrialsonplantspriortofull-scaletreatment.Forsomesubjects,theresultsarebasedononeyear’strialonly.* Somecultivarshaveshownmoderatesusceptibility** Nodamagerecordedinthesetrialsbutoccasionaldamageis

knowntooccur

Weed control in outdoor seed bedsSafeandeffectiveweedcontrolinoutdoorseed bedspresentsasignificantchallengeforHNSgrowers,complicatedsomewhatbytheparticularsusceptibility ofsmallseededcropssuchasalder,birch,hawthornandwhitebeamtosomeherbicidesandtheirvulnerabilitytoweedcompetitionwhileestablishing.Good nursery hygiene and crop husbandry are an essential starting point, helping to keep background weedpressuresinsurroundingnon-cropareassuch asheadlandsandpathwaysundercontrol,aided byprompthandweedingtoremoveweedsbefore theyflower.Othercontrolmeasuresincludethestaleseed bed technique, soil sterilisation and the use of residualherbicides.Bothhandweedingandsoilsterilisationare expensiveforgrowers.Research,therefore,hasfocusedonreducingthesecostsbytriallinglowerrates of Basamid (dazomet), the main soil sterilant nowusedbyHNSgrowersfollowingthelossofmethylbromide in 2005, and screening a range of residual herbicide products to use either as supplements to soil sterilisation or as an alternative, in pre- and post-crop emergenceprogrammes.Stale seed bed techniqueThisculturaltechniquecanbeusedtoattainweed-freeseed beds prior to crop germination but must be done withgreatcare,ascorrecttimingiscriticalforittobesafeandeffective.Itinvolvesusingcontactherbicidesbothbeforeandafterseedsowingtoeradicateanyweedseedlingspresent.Thefinalapplicationrequiresprecise timing and should be made to catch the latest flushofweedspossible,atleastthreetofourdaysbeforecropemergence.Ifappliedtoosoon,subsequentweedsmaybemissedand,ifappliedtoolate,cropseedlingscouldbedamaged.Donecorrectly,itisatimelyandefficientmethodofculturalweedcontrolbutonethatisshort-term,inthatthereisnoresidualeffecttomaintainweedcontrolbeyondcropgermination.A number of contact herbicides including Reglone (diquat) currently have a label approval for use in this way,whiletheuseofShark(carfentrazone-ethyl)isvia off-labelapproval(EAMU).

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Soil sterilisationSoil sterilisation is a common technique, usually done duringtheautumnpriortoseedsowinginspring(althoughitcanbedoneearlierforautumnsowncrops).Ithastheaddedbenefitofprovidingsomecontrolofsoil-bornediseasesandnematodesaswellasweedseeds.However,successfulsoilsterilisationdependson several factors, including soil type, correct soil preparation,adequatesoiltemperaturesandsufficientsoilmoisture.Available as a granular formulation, Basamid (dazomet) can be applied relatively quickly and easily by rotary cultivationwithouttheneedforspecialistcontractors.Oncontactwithmoistsoil,agasisreleasedandthismust be retained by immediately sealing the surface, either by polythene sheeting (the preferred method), floodingwithwaterto‘puddle’thesoilsurfaceorheavyrolling to compact the soil surface (only suitable for outdoorsterilisationintheautumnwhenfollowedbyadequaterainfalltomaintainagoodseal).Afteraperiodof14daysinwarmsoils(10°Candabove)or28daysincoldsoils,thesealisremoved.Thesoilis then lightly cultivated to enable any traces of gas to disperse, taking particular care to avoid disturbing any unsterilisedsoilbeneaththetreatedzone,otherwisecontaminationwilloccur.Afterafurther14days(warmsoils) or 28 days (cold soils), a standard safety test (‘cress test’) as per the product label should be carried outpriortoanyseedsowingorplanting.Whilereasonablyeffective,soilsterilisationcanbeexpensiveandAHDBHorticultureprojectHNS31:Evaluation of weed control treatments in tree and shrub seed beds and first outdoor transplants, examined several herbicide treatments and the use of a lowrateofBasamidapplication(100kg/hacomparedtotherecommendedrateof380kg/ha)rakedintothetop5cmoftheseedbedsurface.BothratesofBasamidworkedwell,withthelowerrateachievingsimilarweedcontrol levels to those of the recommended rate for at leasttwotothreemonthsfollowingseedsowing,savingalmost75%onchemicalcosts.Bothtreatmentsalsoledtoimprovedseedgerminationandseedlingvigour.IfweedcontrolistheprincipalreasonforusingBasamid,thereducedrate(100kg/ha)appliedtothetop5cmofsoilisaviableoptionandwouldprovideconsiderablesavings.However,thelowerratewillnotgive adequate control of soil-borne fungal diseases andnematodes,shouldthisbeafurtherrequirement.TheuseofBasamidisnowrestrictedtoapplication ofnomorethanoneyearinthreeonthesamesite.Residual herbicidesCurrently,therearenoresidualherbicideswith labelrecommendationsspecificallyforuseon nurserystockseedbeds.However,therearecurrently off-labelapprovals(EAMU)fortheuseofStompAqua(pendimethalin) and Goltix 70 SC (metamitron) both usedatthegrower’sownrisk.

Early work with herbicidesWhile some of the herbicide treatments in the seed bed elementofHNS31gavegoodweedcontrolinbothyears of the trial, they also caused a degree of crop loss anddamage.AHDBHorticultureprojectHNS31a:Tree and shrub seed beds: continued evaluation of weed control treatmentsdevelopedthisworkoverarangeofHNSsubjects,aimingto:

• Determine suitable application rates for the most promisingherbicidesidentifiedintheoriginalwork,applied pre- and post-crop emergence

• EstablishiflowerratesofBasamidcouldbeused incombinationwithherbicidesappliedpost-cropemergence to achieve satisfactory levels of weedcontrol

Unfortunately, the products that gave the highest levels ofweedcontrol,namelyButisanS(metazachlor),Flexidor 125 (isoxaben) and lenacil also caused the most cropdamage,althoughsomeHNSspeciesdidshowareasonablelevelofcroptolerance.Oneapproachwhenusingthemoreeffectiveresidualherbicideswithtolerantspeciesistoapplythematlowrateswithtop-uptreatmentsasrequired.ThissystemhasbeenadoptedbysomeHNSgrowers,withprogrammesbasedonlowratesofDevrinol(napropamide)andFlexidor500.ThethreeBasamidtreatments(50kg/ha,100kg/haand 380kg/ha)producedgoodlevelsofweedcontrolwithlittledifferencebetweenthe380kg/haand100kg/harates.Thelowestrateinitiallygaveapoorerlevelofweedcontrolalthoughthiswasimprovedbysubsequentpost-crop emergence applications of Flexidor 125, highlightingscopeforcombininglowratesofBasamidwithreducedratesofsuitableherbicidessuchasFlexidor 125 and Butisan S (although application of theactiveingredientmetazachlorisnowrestrictedto nomorethan1kg/hainathree-yearperiodonthe samesite).Suchherbicideuseisoff-labelandatgrowers’ownrisk.Continued work with herbicidesFurthertrialswork(AHDBHorticultureprojectHNS155:Herbicide screening for tree seed beds), screened arangeofherbicideproductsatdifferentapplicationratesondifferentsoiltypesforsafeandeffectivepre-andpost-cropemergenceweedcontrol,includingsingletreatmentsandsometankmixtures.Aselectionof key small seeded species (Alnus glutinosa, Betula pendula, Crataegus monogyna and Sorbus aucuparia) andsomewithlargerseeds(Acer campestre, Cornus alba, Fraxinus excelsior and Rosa rubiginosa)wereincluded.Atthesametime,earlierherbicideresearchwaspublishedbyForestResearchmakingfurtherinformationavailable.Theselatertrialsconfirmedthatformulationsofpendimethalin (such as Stomp Aqua) are probably the safestoftheresidualherbicideoptions,withthewidestrangeofspeciesshowingtolerance.However,formanyof the small seeded species, the rate of use is relatively

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low(1litre/ha)andthismaycompromisethelevelofweedcontrol.ForestResearchsuggestedtheuseofStompAquatankmixedwithDevrinolforselectedtolerantspeciesasgivingagoodbroadleavedweedcontrol spectrum, although the use of Devrinol is limited totheperiodNovembertoApril.TheresultsfromHNS155alsosuggestedthatCentium360 CS (clomazone), Dual Gold (s-metolachlor) or GoltixWG(nowGoltix70SC)couldbeusedatlowratestoimprovetheweedcontrolspectrumofStompAqua;theprevailingweedspectruminthetrialsincludedannualmeadowgrass,blackbindweed,fat-hen,groundsel,smallleafnettle,knotgrass,fieldpansy,mayweed,shepherd’spurseandcommonspeedwell.Results also suggested a possible role for Springbok (metazachlor+dimethenamid-P) but subsequent commercialexperiencehasshownthatunacceptablestuntingcansometimesoccur.Noneofthetreatmentsprovidedcompleteresidualweedcontrolthroughoutthelifeofthecrop,althoughitwaspossibletomaintainareasonablelevelofweedcontrolforthefirsttwomonthswhenseedlingcropsareespeciallyvulnerabletoweedcompetition.Post-cropemergenceweedcontrolusingherbicidestokeepseedbedscleanismoredifficultduetoagreaterriskofcropdamage.HNS155didincludeamorelimited series of trials testing post-emergence herbicides forcropsafetyandefficacy.Theonlyexperimentaltreatments to scorch, stunt or kill existing seedling weedswereCentium360CS,Dancer(phenmedipham,an EAMU currently covers use of a similar product, CorzalSC)andGoltixWG.Thecropsafetyresults areincludedinTable21(opposite).Treatmentsweremadewhenthecropwasatthecotyledonorcotyledontotwotrue-leafstageandweedswerenolargerthantwotrue-leaves.Full details of all treatments, timings, rates and crop tolerancecanbefoundinthefinalprojectAHDBHorticulturereportsforHNS31,HNS31aandHNS155.Growersareadvisedtorefertothesebeforeapplyingany treatments and then, on a small-scale trial basis first,tocheckcropsafetybeforewideruse.Currently,Butisan S and Flexidor 500 (label approval) and Goltix 70 SCandStompAqua(viaEAMU)canbeusedoverHNSpost-cropemergence,althoughnonehavespecificlabelrecommendations for use over seed beds and such use ismadeatthegrowers’ownrisk.TankmixeswerealsoconsideredforremovingexistingweedandmaintainingweedcontrolandthemosteffectivewereDancer+GoltixWGandDancer+Springbok.However,thesewereonlysafe on Acer and Crataegus, although the latter combination causedlesslossofvigour.Centium360SCwasasaferpost-emergence treatment and could be used on Betula, Crataegus, Fraxinus and Sorbus.

SuccessfulweedcontrolinseedbedscontainingQuercus and Sorbus

108 Aftercare

Table21.Summaryoftheeffectsofarangeofherbicidesontreeandshrubgerminationandseedlinggrowth

Herbicide product

Cor

zal

SC

Butis

an

S

Cen

tium

36

0 C

S

Dev

rinol

Dua

l G

old

Flex

idor

50

0

Gol

tix

70 S

C

Intru

der

Stom

p Aq

ua

Venz

ar

500

SC

Approval status

EAM

U

Labe

l

EAM

U

LTAE

U

EAM

U

Labe

l

LTAE

U

Labe

l

EAM

U

LTAE

U

Pre or post (P) crop emergence P

Pre/

P

Pre/

P

Pre

Pre

Pre/

P

Pre/

P

P Pre

Pre/

P

Acer campestreGerminationVigour/phytotoxicity

Acer platanoidesGerminationVigour/phytotoxicity

Acer pseudoplatanus

GerminationVigour/phytotoxicity

Acer rubrumGerminationVigour/phytotoxicity

Alnus glutinosaGerminationVigour/phytotoxicity

Betula pendulaGerminationVigour/phytotoxicity

Carpinus betulusGerminationVigour/phytotoxicity

Cornus albaGerminationVigour/phytotoxicity

Cornus sanguineaGerminationVigour/phytotoxicity

Corylus avellanaGerminationVigour/phytotoxicity

Cotoneaster franchetti

GerminationVigour/phytotoxicity

Crategus monogynaGerminationVigour/phytotoxicity

Fagus sylvaticaGerminationVigour/phytotoxicity

Gleditsia triacanthosGerminationVigour/phytotoxicity

Prunus aviumGerminationVigour/phytotoxicity

Prunus padusGerminationVigour/phytotoxicity

Quercus roburGerminationVigour/phytotoxicity

Rosa rubiginosaGerminationVigour/phytotoxicity

Sorbus aucupariaGerminationVigour/phytotoxicity

Sorbus intermediaGerminationVigour/phytotoxicity

Susceptible: Unacceptable crop damage normally occurs – do not treat Label LabelapprovalforuseonHNSModerately susceptible: Some crop damage may occur but plants normallygrowaway

EAMU Off-labelapprovalviaanExtensionofApprovalforMinorUse (growers’ownrisk)

Tolerant: Crop damage does not normally occur LTAEU Off-labelapprovalundertheLongTermArrangementsforExtension ofUse(growers’ownrisk)

Table21.Summaryoftheeffectsofarangeofherbicidesontreeandshrubgerminationandseedlinggrowth(continued)

Aftercare 109

Product Active ingredient and concentration Product rates

Corzal SC Phenmedipham(160g/l) 2.5litres/ha

Butisan S Metazachlor(500g/l) 1.5litres/ha

Centium 360 CS Clomazone(360g/l) 0.125–0.250litres/ha

Devrinol Napropamide(450g/l) 2.2–5.0litres/ha

Dual Gold S-metolachlor(960g/l) 0.8litres/ha

Flexidor 500 Isoxaben(500g/l) 0.8litres/ha

Goltix 70 SC Metamitron(700g/l) 1.5–3.0litres/ha

Intruder Chlorpropham(400g/l) 2.0litres/ha

Stomp 400 SC equivalent to Stomp Aqua Pendimethalin(400g/l) Pendimethalin(455g/l)

1.0–3.0litres/ha 0.88–2.64litres/ha

Venzar 500 SC Lenacil(500g/l) 0.4litre/ha

Post‑rooting nutritionHealthy,well-rootedcuttingsthatareuniformandtrueto type are the essential starting point of high-quality production.However,theyandseedraisedmaterialoften remain in their trays for lengthy periods and can become starved before potting on, particularly in the absenceofcontrolledreleasefertilisers.Thisleadstodelayedestablishment,slowergrowth,increasedsusceptibilitytopest,diseaseandweedproblems andpooroveralluniformity,whichisoftenreflectedinthefinalgradeout.Althoughworkhasbeenundertakenonpost-rootingnutrition,thesedifficultiesalsounderlinetheimportanceofaccuratedemandforecastingandrecord-keeping.For best results, adequate and balanced nutrition isessentialthroughoutthepropagationprocess. Veryquickgrowingcropsareunlikelytorequiremuchsupplementarynutrition,providedtheplantsfromwhichpropagationmaterialistakenareingoodcondition.Controlled release fertilisersConsiderableworkhasbeendonewiththeincorporationof controlled release fertilisers in propagation media, to providegradualnutritionduringandfollowingrooting ofcuttings.While the nutrient release of such products is temperature related and high temperatures can trigger ‘flash’release,whichmaydamageyoungroots,theinclusion of bark in the rooting medium enables their safeuse,atlowrates,inpropagationsituations.Withloose-filledandpre-formedmodules,mini-granulecontrolled release fertilisers ensure safe and uniform distribution.Suchproductsare,however,relativelyshort-termandsupplementaryfeedingwillberequiredforlonger-termcrops.

Theinclusionoflowratecontrolledreleasefertiliserswithbarkinthe propagation medium deliver safe and gradual nutrition

Liquid feedingEarlyworkatHRIEfford,beforethearrivalof controlledreleasefertilisernutrition,investigatedwaysof maintaining and improving the quality of rooted materialpriortopotting.Initialtrialsuseddifferentliquidfeedtreatments,beginningfourweeksaftercuttingshadbeenweanedandcontinuedthroughuntilpottingon:

• 50 ppm nitrogen + 50 ppm potassium applied every 1–2weeksdependingonfrequencyofwatering

• 50 ppm nitrogen + 50 ppm phosphate + 50 ppm potassiumappliedeveryonetotwoweeksasabove

The trials used a range of autumn struck cuttings (including: Berberis stenophylla, various Chamaecyparis, Cytisus, Elaeagnus, Ilex and Viburnum x burkwoodii) rootedunderpolythene.Rootedmaterialwasweanedand then held under cold glass before potting in latespring.

110 Aftercare

Inallcases,therewasastrikingimprovementinqualityandgrowthofcuttingswhereafeedprogrammehadbeenusedfollowingweaning,relativetotheuntreatedcontrol.Thenitrogenandpotassiumfeedingregimemaintainedcuttingqualitywithoutexcessivegrowthoccurring (enabling cuttings to be successfully held intrays)whilethenitrogen,phosphateandpotassiumregimepromotedrapidearlygrowthinthetray,aswellasmaintainingquality(althoughearlierpottingwasrequiredtopreventovercrowdinginthetray).

Thebenefitofpost-rootingnutritionusingliquidfeeding(middleand right trays)

Theeffectsoffeedingbecamemorepronouncedthelongerthecuttingswereheldinthetrays.Whilethecuttings established satisfactorily from all treatments, the nitrogen and potassium, and nitrogen, phosphate andpotassiumfedmaterialgrewawayfasterandmoreuniformlythanthenon-fedcuttings.Theeffectswerestill visible some six months after potting on, especially wherephosphatehadbeenincluded.

Thebenefitofnutritionduringweaningandafter:cuttingstotheleftnofeedandtotherightwithliquidfeeding

Table22summarisestheeffectsofthedifferentfeedingtreatmentsfromthefinaltrialinthisseriesofwork.

Table22.Effectsofliquidfeedingtreatmentsonplantgrowthsixmonthsafterpotting,dryweight(g/plant)

Species Time of potting

Feed treatment after rooting

Nil N:K N:P:K

Elaeagnus pungens ‘Maculata’

June 2.4 2.6 2.9

August 0.8 0.8 1.0

Viburnum burkwoodii

June 2.9 5.0 5.4

August 1.5 1.7 2.4

Chamaecyparis lawsoniana ‘EllwoodsGold’

June 8.1 8.8 8.9

August 2.0 2.1 3.4

Chamaecyparis pisifera ‘Boulevard’

June 5.3 5.8 6.2

August 1.1 1.3 2.3

Chamaecyparis pisifera ‘Squarrosa Sulphurea’

June 8.0 8.2 9.0

August 1.3 1.8 2.3

Oneofthedifficulties,however,withliquidfeedingduringtheautumnandwinterperiodisthelimitedrequirementofrootedcuttingsforwater,makingit easytowaterlogthemunlessfrequencyofapplication is reduced, so limiting the amount of feed that can actuallybeapplied.Nutrition of rooted cuttings in modulesSupplementary feeding to maintain cutting quality followingrooting,whileclearlybeneficial,canbe|difficultwithsmallvolumemodules,particularlywhensuch material has to be held for lengthy periods prior topottingon.Notfeedingleadstonutrientstarvedplantswhileweeklyfeedingwithabalancedregimemaycreateexcessivegrowthandunwantedcompetitionamongcuttingsinthetray.Omittingphosphatehelpstoavoidexcessivegrowthwhilepreservingfoliagecolour,enabling rooted cuttings to be held for lengthy periods beforepottingon.However,cuttingscanbecomeratherhardandinactiveafter periods of phosphate restriction and, to address this,AHDBHorticultureprojectHNS90:Nursery stock propagation: nutrition of rooted cuttings in modular trays,aimedtoappraisethepotentialbenefitsofliquidfeedregimeswithandwithoutphosphateonmodule rooted cuttings held for lengthy periods before transplanting,comparetheeffectsofusingcontrolledrelease fertiliser mini-granules in the rooting medium withliquidfeedregimesonplantqualityfollowingpottingandassesstheeffectofnutritionalcompositionandtreatmentregimeontheeffectivenessofnutrient‘trigger’ treatments (a pre-potting liquid feed to encourageplantgrowth).Thesewereliquidfeedregimeswithphosphateappliedshortlybeforepotting,withtheaimofpromotingactivegrowthafterpottingon.

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Theworkusedwinterstruckcuttings(Choisya ternata and Juniperus communis ‘Repanda’) and summer struck cuttings (Azalea ‘Rose Greeley’ and Cotoneaster dammeri ‘Coral Beauty’) rooted in peat:bark in small plug(55ml)moduletrays.Rootedcuttingswereheldforeitherthreemonths(winterstruckcuttings)orfivemonths (summer struck material) and during this period given supplementary nutrition either by liquid feed or controlledreleasefertilisermini-granules.Each of the treatments also received ‘trigger’ nutrient treatments prior to potting into a pre-mixed peat-based growingmedium.Effects of liquid feedingThreefeedingregimeswereassessed,including:no liquid feed (control), 50 ppm nitrogen + 50 ppm potassiumappliedeverytwoweeksand50ppmnitrogen + 25 ppm phosphate + 50 ppm potassium also appliedfortnightly.Finalobservationsweremadefourmonthslater.Linerplantqualitywasnotimprovedinanyofthespecies by the nitrogen and potassium treatment (although, as highlighted earlier, it does maintain cutting qualitywithoutgeneratingunwantedextensiongrowthandcrowdinginthetray).Incontrast,theinclusionofphosphate gave very marked quality improvements in all fourspecies;plantsweregenerallybushier,largerandhadgreaterdryweights(exceptJuniperus).Effects of controlled release fertilisersMini-granuleswereincorporatedintotherootingmediumat0.5kg/m3(winterstruckcuttings)and0.75kg/m3(summercuttings)andcomparedwithanuntreated control and liquid feed treatment (50 ppm nitrogen+25ppmphosphate+50ppmpotassium).Noadditionalliquidfeedwasappliedtothecontrolledreleasefertilisertreatmentwhiletherootedcuttingswerebeingheld,butnutrienttriggertreatmentsweregiven (200 ppm nitrogen + 150 ppm phosphate) six weeksbeforepottingon.Overall, in comparison to the untreated control, the controlledreleasefertiliserwassignificantlybeneficialinthewinterstruckChoisya and Juniperus but of no orlittlebenefitinthesummerpropagatedAzalea and Cotoneaster. Thereasonsforthelatterresultwereunclear but it may have been related to the diminishing effectofthecontrolledreleasefertiliserfollowing(earlier)summerpropagation.Whencomparingthecontrolledreleasefertiliserwiththeliquidfeedprogramme,thelattertreatmentwasofgreatbenefitwithCotoneaster and Azalea,whilethecontrolledreleasefertiliserwasbetterwith Choisya and Juniperus.Theapparentspeciesspecificityarisingfromtheseresultsmay,however,havebeenmorerelatedtothetimeofyearwhenthecuttingswerestruck.Thus,thetwospeciesbenefitingmostfromthecontrolledreleasefertilisertreatmentwerebothwinterstruckandsohadarelativelyshortholdingperiodbeforepotting.Thesummer struck Cotoneaster and Azalea,withthelongerholdingperiod,didnotshowanybenefit,suggestingthat the controlled release fertiliser had supplied all its

availablenutrientsbytheendoftheperiodandwas out-performedbytheliquidfeedtreatments.Controlled release fertiliser mini-granules can normally be expected to provide nutrients for three to four months depending on seasonal conditions and cultural regimes.Whentheholdingperiodexceedsthis,afollow-onliquidfeedregimeisrequiredtomaintaincuttingquality.Effects of trigger treatmentsFournutritionaltriggerswerealsoassessed,comprisingtwolevelsofnitrogen(100and200ppm)andtwolevelsofphosphate(150and300ppm).Eachwasappliedtwoorthreetimes,withtwoweeksbetweensuccessiveapplications.Triggerapplicationsbeganeithersixweeksbeforepotting,whenthreeapplicationsweregiven,orfourorsixweeksbeforepottingwhentwoapplicationsweregiven.Therewerenomajortrendsbetweenthetreatmentsorindication that a trigger treatment can compensate for thereducedgrowthandqualityarisingfroma50ppmnitrogen + 50 ppm potassium maintenance feed rather thanonewiththeadditionof25ppmphosphate.Onthebasisofthiswork,triggertreatmentsarenotrecommended as substitutes for maintenance feeding usingabalancednutrientfeedcontainingphosphate.Cultural suggestionsAsaresultoftheaboveandotherresearchwork,thefollowingculturalrecommendationscanbemade:

• Ensure stock plants and nursery crops used for propagation material have adequate nutrient reserves tomaintainstrong,healthygrowthsuitableforuseasquality cuttings

• Liquidorfoliarfeedquickgrowingcontainerstockplants ahead of propagation to boost nutrient reservesforrooting.Continuethisprogrammethroughrooting,weaningandthereafter.Avoidanexcessofnitrogen,whichwillreducerooting

• When devising feeding regimes consider the vigour and requirements of crops, the propagation and weaningenvironment,therootingmediumandthefertiliser used

• Userootingmediawithcontrolledrelease mini-granulesincorporatedwhenrootedcuttingsareexpectedtobeheldforasignificantperiodbeforepotting on

• Useabalancedliquidfeedattwo-weekintervalsifrootedcuttingswithcontrolledreleasefertiliser mini-granules are held beyond this period

• Withslowerrootingautumnpropagatedmaterial,controlled release fertilisers provide sustained and balancedpost-rootingnutritionefficientlyoveralonger timeframe

• Longer-term, crops rooted during the spring and summerperiodandoverwinteredalsobenefitfromtheinclusion of controlled release fertiliser but should also bepottedpromptly.Ensurecontrolledreleasefertiliserisuniformlyincorporatedwithintherootingmedium

112 Aftercare

• For short-term crops, the inclusion of controlled release fertilisers is not essential, providing the nursery is geared up to regular liquid feeding

Growth controlItisoftennecessarytocontrolthegrowthofrootedcuttings and young liners either to maintain or improve theirqualityortoschedulethem.Pruningandtrimmingofpropagationandlinercropsiswidelypracticedandthereissomeuseofchemicalplantgrowthregulatorswiththelatter,butthereisalsoawiderangeofculturalalternativesforcontrollinggrowth,including:

• Growingmorecompactorslowergrowingspecies

• Scheduling plant production

• Controlling environmental temperatures

• Controlling light intensity and quality

• Managing the frequency and amount of irrigation provided

• Manipulating nutrition and employing nutrient restriction

• Restrictinggrowthbyphysicalmeans

• Using cold storage facilities

• Using outdoor production facilities

Pruning of liners and plug plantsPruning and trimming of rooted cuttings and liners to reduce plant height and shape young plants is a crucialpartofqualityproduction,particularlywithquickgrowing,vigoroussubjectsandintheabsenceofotherformsofgrowthcontrol.Itisalsoimportantwherethepotting on of rooted material or young liners is delayed topreventexcessivegrowth.Traditionallyundertakenbyhand,machineryisnowavailabletoeaseandspeedupthework,someofwhichalsocollectsprunedplantmaterialastheworkproceeds.Timingisoftencritical.Withmostconifersandshrubsrespondingwelltobeingprunedwhenactivelygrowing,forexample,asalinerinmidsummer.However,ifthisisdonelaterintheseason,soforcingnewgrowththatdoesn’thavetimetoripen,winterlossesorplantdeathmayensure.Anyformativestructuralpruningwithspringand early summer propagated material should be done inmidsummer,withonlylighttrimmingtotidytakingplaceduringtheautumn.AHDBHorticultureprojectHNS40:Pruning for quality with minimum reduction in size, aimed to understandmoreabouthowplantsrespondtodifferentpruningtechniquesandsoidentifystrategiesbywhichqualitycanbeenhanced;akeyconsiderationwasthatpruningshouldnotreduceplantsizeunnecessarily.Resultsshowedthatwhiledifferentspeciesrespondeddifferentlytopruning,someguidingprinciplescouldbederivedinrelationtovigourofgrowthineachspecies.Generally, the more vigorous the species, the greater thepruningbenefitintermsofbuddevelopmentand

newbasalbranchformation.SeverepruningwasusuallydetrimentaltoslowergrowingsubjectssuchasCotinus, Garrya and Viburnum, delaying branch formation and significantlyreducingoverallplantsize.Timingwasalsocritical,withsevereautumnorwinterpruningmakinglessvigorousplantsmoresusceptibletooverwinteringstresses.Forthesesubjects,nopruningorlightpruningwasoftenthebesttreatment,althoughthefrequencyofpruningtopromoteoptimumgrowthcharacteristicscouldstillvarywithspecies,forexample,Syringawasbest pruned once, Garrya threetimes.Althoughthisworkfocusedonlargerplantmaterial,italsohasimplicationsforlinerandlargeplugplantproducers.

Regular trimming is an important part of quality plant production

Chemical plant growth regulatorsPlantgrowthregulatorsarechemicalcompoundsthataltergrowthanddevelopmentbymodifyingtheplant’snaturalhormonebalance.Sometimes,itismoreappropriatetousechemicalplantgrowthregulatorstoattain the desired results rather than cultural methods, however,theyshouldnotbeusedasasubstituteforgoodcropculture.The products should be applied at a particular physiological stage in the development of the plant and notscheduledbytime.Aprogrammeoftreatmentsisusuallyrequiredwithmostcrops;theyshouldnotbeappliedwhengrowthhasalreadybecomeexcessiveortooadvanced.Currently,productsusedintheUKarebasedprimarilyonthreemainactiveingredients.Stabilan750containschlormequat,B-NineSGandDazideEnhancecontain daminozide and Bonzi and Pirouette contain paclobutrazol.Afurtherproduct,RegalisPlus,whichcontains prohexadione-calcium, can also be used in ornamentalplantproductionviaanEAMU.Theykeepplant height in check by reducing the stem internode lengthbuttheyalsohaveaneffectonbranching,planthabit,foliagecolourandflowering.

Aftercare 113

Experiencewithgrowthregulatorsandpotlinersisquitelimited,althoughsomegrowersuselowratesequentialprogrammesofproductstocontrolgrowthunderprotection,onceabasicbranchframeworkhasbeenestablished.Thereisalsosomeuseofproductsforgrowthcontrolinherbaceousperennialsgrownfor retailsales.There may be scope to adapt these programmes for usewithrootedHNScuttingsandliners,wheregrowthcontrolunderprotectionisrequired.B-NineSGorDazideEnhancegivemoderategrowthcontrolandtheyare likely to be the most suitable for use in young plant production,ratherthanBonziorPirouettewhoseeffectsarerelativelymoreintense.

Choice of species or varietyWherefeasibleandpractical,compactorlowvigourspeciesorvarietiesshouldbeselectedandgrowntoreducetheneedtoresorttoanykindofgrowthcontrol.Thisisasimpleyetusefulguidingprincipletobeawareof.However,choiceofspeciesorvarietyisusuallydetermined by sales requirements, and they are often selectedforattributesotherthanvigourthatmayoffer acommercialadvantage.

Accurate plant schedulingSchedulingaimstomatchsupplywithdemandand,therefore,minimisecropwastage.Bypropagatingto a production programme on planned, sequential dates andcontrollingthegrowingenvironmentaccordingly,plantscanbeproducedtotheagreedspecificationwhenrequired.However,seasonalweatherconditionsinvariably determine market demand and can, in turn,delaythehandlingofrootedcuttingsorliners.Transplanting vigorous crops later in the season is asimpleandpracticalwayofcontrollinggrowth.

Controlling environmental temperaturesLoweringthemeangrowingtemperaturecanalsobeaneffectivewaytorestrictordelaygrowthwithpropagationandlinercropsgrownunderprotection,althoughthiswillslowdownplantdevelopmentandincreaseproductiontimes.Conversely,raisingthetemperature, by reducing ventilation or using space heaters,willusuallyadvancegrowthbutcareisrequiredtoavoidsoft,excessivegrowth.

Controlling light intensity and qualityLowlightlevelscauseplantstostretchandsoreducequality, therefore, light transmission levels through glasshouses and polythene tunnels need to be maximised.Clean,goodqualityglasstransmitsaround88%oflightbutshadowingfromstructuralframeworksandthermalscreens,etc.willreducethis.Dirtyglasswillreducelighttransmissionfurther(typically,byabout20%),whiledirtypolythenecanreducelighttransmissionevenmore(upto30%).Plantsarealsosensitivetolightqualityaswellaslightintensity;increasing the UV, blue or the red to far red ratio of light, forexample,canallcontributetowardsgrowthcontrol.

Spectral filtersPlasticfilmswithdifferentlightspectraltransmissionpropertieshavebeendeveloped,whichcanbeusedasameansofcontrollinggrowth,floweringtimeandfoliagecolourwithsomeHNSspecies.Thesefilms alterthewavelengthoflightpassingthroughthem andhavebeenshown(forexample,inAHDBHorticultureprojectHNS108:Growth of a range of nursery stock subjects under different coloured and spectral filter films), to reduce plant height, increase branching and increase leaf colour intensity in a range ofplantspecies.However,theintensityoftheireffectsvarieswithspecies.In a parallel study, the rooting of cuttings taken from plantsgrownunderspectralfilterswasalsoevaluated.For the majority of the species tested, altering the light spectrum over the stock plants appeared to have verylittleeffectontherootingpercentageofcuttingstakenfromthem.WiththeexceptionoftheusuallydifficulttorootCotinus andtheslowrootingconifer, X Cupressocyparis leylandii, rooting percentages tendedtobehighregardlessoftreatment.Artificial lightingArtificiallightinghasbeenusedincommercialhorticulturefor many years to enhance natural light levels and extend day length, thereby improving plant quality and enabling the programmed production of protected crops, most notablybeddingplants,potplantsandcutflowers.Essentially,therearethreedifferenttechniquesorapproaches used for lighting crops:

• Supplementary lighting: this is photosynthetic lighting and involves the use of high intensity lighting (5,000–15,000 lux) to enhance natural light levels by addingartificiallighttonaturaldaylightorbyextending the natural day into the night period or a combinationofbothtopromoteplantgrowth.Usually, high pressure sodium lamps are used for this purpose.Itisusedwithnurserystockunderprotection, for example, to aid seed germination, shorten production times and improve quality

• Photoperiodic lighting: this is non-photosynthetic lighting.Assuch,amuchlower(around50lux)lightintensity is used to manipulate rather than supplement natural daylight and so stimulate out of season responses for many species, particularly in respectoffloweringanddormancy.Itisusedtoextendnaturaldaylengtheitheratduskordawnorbyaperiodoflightthatbreaksthenightintotwodark phases (‘night-break’ lighting)

• Replacementlighting:thisdiffersfromsupplementaryand photoperiodic lighting in that it is deployed to eithertotallyorpartiallyreplacedaylightwithartificiallight.Mostusuallyittakesplaceinaninsulatedgrowingorgerminationroomfromwhichnaturaldaylightisexcluded.Suchstructuresarewidely used for seed propagation and, in micropropagation, wheretheprincipalobjectiveistoachieverapidanduniform germination or root initiation using a high degree of control over the light environment

114 Aftercare

Growthchambersprovideclosecontrolofgrowth

Light application to stock plantsSupplementary lighting can be used to advance the growthofstockplantstoextendthepropagationseason and enable a greater number of cuttings to beharvestedfromeachplant.InHNS42and42a:Supplementary lighting for alpines, herbaceous and hardy nursery stock species, early growthon3-litreClematis ‘MissBateman’,grownasstockplantsina16-hourphotoperiodwithhighpressure sodium lamps, enabled cuttings to be takenearlierthanfromthosegrowninan8-hourday,indicatingwiderpotentialformanipulatingstock plantgrowth.Effects of light application to stock plants on subsequent rooting of cuttingsOtherstudieshavealsoconsideredtheeffectsof thephotoperiodtowhichstockplantsaresubjected onthesubsequentrootingofHNScuttings.Cuttings of Cornus florida, for example, (Waxman, 1957) taken fromstockplantsgrownforfourmonthsundera 15-hour photoperiod rooted better than those from stockplantsgrownforthesamedurationundera 9-hour photoperiod and similar results have been reportedwithRhododendron obtusum japonicum cultivars‘Hinodegriri’and‘Snow’(BarbaandPokorny,1975).However,therootingofcuttingsofIlex crenata ‘Hetzii’ improved as increasing numbers of short days weregiventostockplantsgrownduringthesummer(Kelly,1965)andTaxus cuspidata‘Nana’hasbeenshown(LamphearandMeahl,1963)torootbestwhencuttingsaretakenbetweenNovemberandFebruary(duringnaturalshortdays).Light application at rootingAmericanresearchworkhasshownthatsomeHNSspecieswillrootbetterandquickerwhengivenlongdaylighting during propagation, including cultivars of Abelia, Cornus, Ilex and Magnolia.AnecdotalUKexperience

alsoindicatessuccesswithX Cupressocyparis leylandii, Chamaecyparis lawsoniana cultivars, Juniperus horizontalis ‘Glauca’, Thuja occidentalis ‘Rheingold’ and Thuja orientalis‘Decussata’whenlitduringrooting.Morespecificstudieswithselectedspecieshavealsoconsidered the responses of cuttings to photoperiodic lighting given during rooting but results have been variable.InworkwithCornus florida cuttings (Waxman 1955,1965)insertedundermistduringJune,rootnumbersincreasedwithdaylengthsof18or24hourscomparedwith9hourornaturaldaylengthtreatments,althoughthepercentagerootingwasthesamethroughout(Table23).Table23.Theeffectofphotoperiodictreatmentontherooting of Cornus florida cuttings (Waxman, 1955, 1965)

Photoperiod Percentage rooting

Average number of roots per cutting

Normaldaylength 100 15.4

9 hours 100 8.50

18 hours 100 25.4

24 hours 100 23.7

Similarly,inmoredetailedstudieswithCornus alba (WhalleyandCockshull,1976),therewaslittledifferenceinpercentagerootingwhencuttingsweregivenlongdaytreatmentsofcontinuouslight(dusktodawn)ora5-hournight-break,incomparisonwithnaturaldaylengths.Themaineffectwasasubsequentincreaseinstemgrowthofplantsrootedunderlongdays.Whencuttingsweretakenintheautumn(whenthenaturaldaylengthwasshorter),rootnumberandpercentagerootingwereincreasedbylongdaytreatments;thisalsoappliedtocuttingsofBerberis ottawensis ‘Superba’ and Viburnum x bodnantense ‘Dawn’whentakenintheautumn(WhalleyandCockshull,1972).Itiswellknownthatindoleaceticacid(IAA,anaturallyoccurring auxin-based plant hormone that promotes rooting) levels may be increased by long photoperiods inbothstemandleaftissue.However,therelationshipbetweenthisandenhancedrootingpromotedbyphotoperiodisnotcompletelyunderstood.Work at Loughall (1978–1979) also considered the effectsofsupplementaryandphotoperiodiclighting(night-break) on the rooting of a range of autumn struck evergreen species (Berberis candidula, Berberis x stenophylla, Ceanothus, Elaeagnus x ebbingei, Escallonia, Euonymus, Ilex, Pittosporum, Pyracantha, Senecio and Viburnum tinus) and conifers (X Cupressocyparis leylandii, Cupressus macrocarpa ‘Lutea’, Chamaecyparis lawsoniana cultivars, Juniperus communis and Thuja occidentalis)undermist,withthesubjectsbeinggrownontoafinishedplanttoassessthefulleffectofthetreatments.

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Cuttingswereplacedunderhighpressuresodium, lowpressuresodiumandtungstenfilamentlampsandanunlitcontrol.Thesodiumlampswerepositionedtoprovide a luminance level of 10,000 lux and used over an 8-hour period from 8:00am to 4:00pm to supplement naturaldaylight.Thetungstenfilamentlampswereusedto provide photoperiodic night-break lighting, giving a minimum light level of 50 lux operated from 11:00pm to2:00am.Only a limited number of subjects responded positively (higher percentage rooting compared to the unlit control) to photoperiodic (night-break) lighting (although increasedspeedofrootingwasrecordedinallsubjects)andseveralgaveanegativeresponse(lowerpercentagerootingcomparedtotheunlitcontrol).However,nearlyallsubjectsshowedapositiveresponsetosupplementarylightingwhenpropagatedduringtheautumn.Asinpreviousyears,somevarietaldifferencesinresponsebetweenlowandhighpressuresodiumlightingwereseen.Ingeneral,theformergavethebetterresults.Some subjects, notably X Cupressocyparis leylandii, failed to respond to any form of lighting and Viburnum tinusgaveanegativeresponsetoalllightingregimes.Thegrowth(measuredasmeanheight)ofthesubsequentlinersintheirrespectivetreatmentswasrecordedthefollowingyearinApril,immediatelybeforepottingintotheirfinalbag-pots(2.5-litre).Theresults,atthispoint,indicatedthatmostcultivarswhensubjectedto photoperiodic lighting produced a larger liner than the control but supplementary lighting produced smaller plants.Plantsgivensupplementarylightingduringrooting had shorter internodes and, in some cases, largerleafnumbers.Photoperiodiclightingand,toalesserextent,supplementarylightingwasthoughttohavecausedsomeflowerbudstohaveaborted.Records of plant height taken later at the end of the firstgrowingseason,showedthat,formanysubjects,plantsthatreceivedsupplementarylightingwentontoproducelargerplants.In18subjects,however,nosignificantdifferencewasrecordedbetweentreatments.Ilex aquifoliumwasslowtobreakinthespringfollowingexposuretosupplementarylight.Thesizeandquality ofalltheothersubjectsatpointofsalewereequalto orbetterthanthecontrol.Theuseofartificiallightingtopromoterootingof severalHNSsubjectswasalsoexaminedatHRI Effordinatrialusinglowintensitynight-breaklighting.In this case, applied from 10:30pm to 3:30am each nightfrominsertionuntilweaning,using60Wtungstenfilamentbulbswithreflectorsspacedat2mcentres,approximately60cmabovethecuttings.The cuttingsweretakenduringOctoberandNovember androotedunderglasswithclearpolytheneusing abasaltemperatureof18°C.Table24summarisestheresultsandshowspositiveresponsesfromtheLawsonscypresscultivars‘Allumii’and ‘Columnaris Glauca’.Similarly,X Cupressocyparis leylandiishowedamarkedimprovementinrootingwithnight-breaklighting.

Givencurrent(high)energycosts,itwouldonlybeeconomictoproducethemostdifficultsubjectsusingsupplementarylighting.Photoperiodiclighting,however,may be of interest at a later stage of propagation followingcallusformation.Table24.Effectsofdaylengthextensionontherootingofconifers

SpeciesPercentage

rootingTime

difference to weaning

(days)Lit Unlit

Chamaecyparis lawsoniana ‘Allumii’ 57 38 43

Chamaecyparis lawsoniana‘Ellwoodii’ 87 80 29

Chamaecyparis lawsoniana ‘Ellwood’sGold’

65 74 14

Chamaecyparis lawsoniana ‘Fletcheri’ 15 45 43

Chamaecyparis lawsoniana ‘Columnaris Glauca’

93 35 54

X Cupressocyparis leylandii 30 12 14

Controlling the frequency and amount of irrigationReducedmoistureregimes,whereplantsareirrigatedlittleandoften,andallowedtobecomestressedbetweenirrigationcycles,willslowgrowthandproducea more compact plant habit (reductions in height of over 30%havebeencommerciallyachieved).However,theregime needs careful monitoring as excessive stress canstuntplants,causeprematureflowerbuddropandreduceplantquality.Sophisticatedmoistureprobesarenowavailabletohelpmonitorthemoisturelevelsin container-growncrops,seeAHDBHorticultureprojectHNS97:Improving the control and efficiency of water use in container-grown hardy ornamental nursery stock.Suchprobescanalsobeconnectedto irrigation systems, providing a degree of automatic irrigationgearedtotheneedsoftheplant.

Nutrition and nutrient restrictionExcessivegrowthcanbeavoidedbyusingappropriateamountsofthecorrecttypesoffertiliser.Lowlevelsofbasefertiliserinthegrowingmedium,forexample,willpreventrapid,earlygrowthandcontrolledreleasefertilisers can be used to provide nutrients as the plant requires them or supplementary liquid feeds can be usedandmatchedtothestageofcropdevelopment.

Controlling growth by physical meansThis approach has its limitations but restricting the root systems of plants by, for example, holding them in modulesorsmallpotsizeswillconstrainplantgrowth.

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However,thisneedstobecarefullymanagedtoavoidstarvation.Growthimbalancescanalsostilloccurifother physical and environmental conditions are not addressed.

Cold storageRooted plugs can be held in cold storage for several daysandevenweekstokeepgrowthincheck,sominimising the amount of bed space used to hold materialbackwithoutasignificantlossinquality.Longer-term,storageoverseveralweeksalsoenablesproductiontobescheduledtomeetspecifictimeframesthatmightotherwisebedifficulttoachieve.The feasibility of using cold storage as a scheduling aid withHNSwasconsideredinAHDBHorticultureprojectHNS113:The feasibility of using low temperature storage as a scheduling aid in nursery stock production.Theabilitytoholdrootedcuttingsinmodules and pot liners for short periods until required wasoneofseveralbenefitsidentifiedduringthestudy,enabling, for example, the development of scheduled pottingprogrammes.Althoughlittleworkhasbeendonetodeterminemoreprecisely the cold storage temperature requirements ofHNSspecieswhenstoredasplugsorliners,3–4°C islikelytobeagoodstartingpoint.Cold storage is also a useful management tool for container-grownstockplants,forexample,todelaygrowth,andsopropagationmaterial,untilitisrequired.Either direct cooled or jacketed stores can be used, although the latter is more suitable, particularly for longer-termstorageandwhereplantsareunwrappedandsomorepronetodryingoutifinadirectcooledstore.The AHDB Horticulture HNS Cold Storage – a grower guideandfactsheet09/05:Low temperature storage of bedding plant plugs, provide more detailed guidance on the use of controlled temperature storage andareusefulpointsofreferencewhenconsideringthistechniquewithHNSplugplantsandliners.

Outdoor productionMoving protected crops to cooler, outdoor locations is alsoausefulwayofcontrollinggrowth;suchmaterialislesslikelytostretchthanifitweregrownentirelyunderprotectionandgrowthrateswillslowdown.Polythenetunnels can be uncovered in summer to save handling, eithermanuallyorbyautomatedroofsystems.Roll-outbenchsystemsareanother,flexibleoption,enablingcropstobequicklymovedwhenrequired.

Overwintering of rooted cuttings and young linersRootedcuttingsandyoungHNSlinersarefrequentlyoverwinteredunderprotectionforpottingonthefollowingseason,particularlyspringandsummerpropagatedmaterial.Suchmaterialcanfailtoestablishandsometimesdiesduringthefirstwinterorisofreducedqualityandvigourthefollowingspring.

While the extent of failure may vary considerably betweenyears,plantspeciesandsituation,mostusuallythetwoprincipalcausesofthisare:

• Directinjurytoyoungplanttissuefollowingexposuretosub-zerotemperatures,oftenwherefrostprotectionmeasureswereinadequate

• Indirectinjuriesinwhichtissuesareexposedtoprolonged but less severe, environmental stress

Frostdamageisoneofthemaincausesofpoorwintersurvivalamong rooted cuttings and liners

Theabilityofcuttingstooverwintersuccessfullyappearstobestronglyspecies-specific,withfailureoftenassociatedwithsomeofthemoredifficult,highervalueHNSsubjects,includingAcer (palmatum), Camellia, Corylopsis, Daphne, Garrya, Magnolia, Rhododendron and Viburnum although even in some of the easier-to-root subjects (such as Ceanothus, Choisya and Hebe),prolongedstressinwinterwillreducecuttingandlinerquality,particularlyinthespring.Waterlogging, frost damage and poor environmental control (notably, unsuitably high relative humidities around dormant cuttings creating ideal conditions for leafdiseasesanddamping-off)areacommonbutavoidablesourceofproblems.Goodcrophusbandry,

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adequate frost protection and prompt application of crop protection measures are essential for successful overwintering.Good nursery hygiene is also paramount, including routine monitoring of cuttings and prompt removal ofdecayingmaterial.Propagationmediaandbedsshouldalsobecleanandwelldrained.

Overwintering failure with rooted cuttingsAHDBHorticultureprojectHNS44:Pre- and post-rooting storage of softwood and hardwood cuttings, investigatedthereasonsforoverwinteringfailureinnewlyrootedcuttings.Foursubjectsconsideredtobedifficulttooverwinter(Acer palmatum ‘Aureum’, Ceanothus ‘Autumnal Blue’, Euphorbia griffithii and Magnolia x soulangeana)wererootedinplugtrays andoverwinteredinpolythenetunnels,glasshouses orcoldstores.Temperature and humidityWhiletheeffectsofvariousoverwinteringstressesvariedwithspecies,ingeneral,exposuretosimulatedfrostwasmostdetrimental.Evenlightfrostsresultedinleaforstemdamageandgrowingmediatemperaturesof-3°Cinvariablyledtoplantdeath,regardlessofspeciesordepthofdormancy.Otherstresseswerealsocritical;Ceanothuswasespecially sensitive to even moderate levels of desiccation and Acer palmatumwaspronetoinjuryassociatedwithhighoverwinteringtemperatures(15–20°C)whengrowninheatedglasshousestructures.LosseswithEuphorbiawerealsoassociatedwithhighhumidityduringtheproject.Coldstorageenhancedcutting viability and led to greater subsequent vigour in somecases,forexample,fasterandstrongergrowthofCeanothus and Magnolia compared to rooted cuttings overwinteredunderpolythene.Rooting and nutritionGenerally,cuttingsthatarepoorlyrootedpriortowinterare more likely to fail, even though stems may appear viableandhealthyformanyweeksfollowingweaning.Lossescanstilloccurwithwell-rootedcuttingsnotsubjectedtosignificantstress,usuallyduetoselectionof poor quality or second grade cuttings, or as a result of rooting cuttings too late in the season or under less thanidealconditions.Whilerootingratesmaybehighin such material, carbohydrate reserves are often quite limited and unable to sustain cuttings successfully overwinter.Preferably,cuttingsshouldbeselectedonlyfromtheyoungest,mostvigorousstockplantmaterial.Afailuretoformstrong,well-developedrootsbeforewinterunderlinestheimportanceoftimelypropagationandlinerpottingtoallowadequatetimefornewrootstofullyestablishbeforethedormantperiod.Thisisparticularlysowithlessvigorous,slowerrootingdeciduoussubjects,whicharealsothinstemmed, such as species or cultivars of Acer palmatum, Berberis, Cornus, Corylopsis, Potentilla and Spiraea, forexample.

Strong,well-developedrootsareoneofthekeystosuccessfuloverwinteringofcuttings

Adequate nutrition of stock plants, cuttings (during andafterrooting)andlinersfollowingpottingisalsoanessentialcomponentofsuccessfuloverwintering;malnourishedmaterialwillstruggletoestablishadequatelyandsowillnotsurvive.

Overwintering strategiesFurtherwork(AHDBHorticultureprojectHNS84:Development of effective overwintering strategies for rooted cuttings and young liners), considered in greaterdetailwhyrootedcuttingsoftenfailtoestablishandthendieduringtheirfirstwinter(manyoftheselossesoccurfollowingrootingandduringtheearlystagesof liner production), focusing on indirect injuries brought aboutbyprolongedexposuretoenvironmentalstress.In such cases, no immediate injury is sustained but resourceswithinplanttissuesgraduallydeclineorcellviability becomes impaired leading to a failure of buds tobreakdormancythefollowingspring.Theworkaimedtodeterminemorefullywhatenvironmentalstressescontributedtowinterlossesunderprotectionandtheextenttowhichfactorsbeforeorduringrootingaffectedwintersurvival.Arangeofsubjectsconsidereddifficulttooverwinterwereusedfortheproject,comprisingAcer palmatum ‘Bloodgood’, Acer palmatum ‘Aureum’, deciduous Azalea, Ceanothus ‘Autumnal Blue’ (representing evergreenspecieswherelossoffoliagequalitycanbesignificantinwinter),Corylus pauciflora, Cotinus coggygria, Magnolia x soulangeana, Rhododendron ‘Coccineum Specoisum’ and Viburnum carlesii ‘Aurora’(Table25).

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Theprojectfoundthefollowingfactorssignificantlyaffectedrootingandwintersurvivalrates:

• Theextenttowhichthestockplantswerepruned• The type and size of cutting

• Thepartofthestockplantfromwhichcuttings weretaken

• Thehandlingofcuttingsfollowingcollection• Theoverwinteringenvironment

• The type and extent of covering material used for frost protection

Oftenthesefactorsinfluencedsurvivability,irrespectiveofrootingpercentage.Forexample,inRhododendron, the percentage take may be high but subsequent survivalwassignificantlyinfluencedbycuttingsize.Stock plant pruningAlthoughtherewassomevariationbetweenspeciesandyears,severaltrendswereidentifiedwhenattemptingtooptimiserootingandcuttingsurvival.Withtheexceptionof Acer, harder pruning of stock material generally led tomorevigorousshootgrowthandtheproductionofcuttingswithgreatersurvivalpotential.

Table25.Theeffectsofstockplantpruningregimesonrootingandwintersurvivalofcuttings

Species and pruning regime

Percentage rooting

Percentage survival

Acer palmatum ‘Bloodgood’

Hard pruning 64 19

Light pruning 94 56

Corylopsis pauciflora

Hard pruning 95 43

Light pruning 86 13

Type and size of cuttingThinstemmedcuttingsoftenrootedwellbutfailedtosurviveoverwinter,incontrast,wintersurvivalofthickerstemmed subjects such as Cotinus, Magnolia and Viburnumwaslargelyunaffectedbycuttingsizeandstemdiameter.For several thin stemmed species, including Acer, Corylopsis and Rhododendron, taking larger or thicker cuttingsoftenimprovedrootingandwintersurvival,most probably on account of their greater carbohydrate content.Inpractice,however,abalanceneedstobestruckbetweenoptimisingcuttingsizeandalaterordelayedharvestingtime.Suchadelaycanreducerootingandsurvival;largercuttingsrootedlaterintheseasonmaynotrootaswellasthosecollectedearlier.Later collected cuttings are also often less active physiologically and very large cuttings can easily stressinsuboptimalpropagationenvironments.

Part of the stock plant from which cuttings are takenInearlytrials,therewereinteractionsbetweenthepropagation environment and the part of the stock plantfromwhichcuttingswereremoved;inthecaseof Rhododendron, the greatest failure occurred among thosecuttingstakenfromthebaseofthestockplant.Handling of cuttingsThewaycuttingsarehandledandstoredbetweencollection and insertion can also reduce subsequent survival, especially in the case of soft, summer cuttings whicharenotkeptcool,shadedandfresh.InHNS84,withMagnolia,forexample,thewintersurvivalofcuttingswasreducedbystoringthemunderpolythenecovers in ambient conditions for 24 hours prior to sticking(eventhoughrootinitiationwasunaffected)comparedtocoldstoringthem(for48hours),whichwasnotdetrimentaltosubsequentsurvivalordevelopment.Overwintering environmentOverwinteringenvironmentswerefoundtoaffectthesurvivalofrootedcuttingsofmanyspecies.Insomesubjects, most notably Acer palmatum ‘Bloodgood’ and Rhododendron,overwinteringinanon-ventilatedpolythene tunnel reduced survival compared to a well-ventilatedstructure,duelargelytothegreaterhumidityofthelatter.Ingeneral,polythenetunnelsshouldbewellventilatedthroughoutthewinterasconditionsallow.The use of cold storage facilities appeared a feasible andmoreeffectivetechnique(comparedtotunnelenvironments) to ensure good survival rates for some species, notably Ceanothus, Corylopsis, Magnolia and for some cutting types, Rhododendron.However,careisrequired to ensure successful transition back to ambient conditions,mostsignificantlyavoidingexcessiveexposuretohightemperaturesandhighlightlevels.Cuttings of Ceanothus and Corylopsiswerealsosusceptibletowinterlossesduetoirregularorinfrequentwateringinsomeoftheenvironments,underliningtheneedtoensurethatcellsdonotdryoutduringwinter.Winter protectionTheprojectalsoconfirmedthatpolypropylenefleecesand ‘bubble’ sheets are useful in providing extra additional frost protection during short-term, radiation frosts;temperaturesundersuchcoverswereoften3–4°Chigherthanthoserecordedoutside.

Using lighting to improve survivabilityThereareoftensituationswheretimelypropagation and liner potting is not possible and using photoperiodiclightingtopromotevegetativegrowth(therebyenhancingwintersurvivalandgivingstrongerplantsthefollowingspring)maybeadvantageous.InastudyontheoverwinteringofarangeofHNSspecies (Loach and Whalley, 1975), long day lighting wascomparedwithunlittreatments,gibberellicacidspray treatments (a naturally occurring plant hormone associatedwithgrowthpromotion)andextendedphotoperiodswithcarbondioxide(atthreetimes

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atmosphericconcentration).Whilesomespecies,suchas Acer saccharinum, responded identically to light and giberellicacid(whichsubstitutesforlongdays),otherswerefarmoreresponsivetolightthangiberellicacid,for example Betula pendula,wherelight,andlightpluscarbondioxidegavegreatestgrowthandamarkedincreaseinpercentagesurvival(Table26).Table26.PercentagesurvivalandfreshweightinBetula pendula 12monthsaftercuttingsweretaken(LoachandWhalley,1975)

Treatment Percentage survival

Fresh weight/plant (g)

Shoot Roots

Control 16 61 33

Giberellic acid, 100ppm,weekly 21 71 46

Extended photoperiod 62 80 42

Extended photoperiod + carbon dioxide

70 90 44

Whilelightingmayreducegrowththefollowingseason,wheresuchhighpercentagewintersurvivalratesasthisare achieved, lighting may have a useful role to play in improvingwintersurvivalofrootedcuttingsandliners.Using long days (night-break lighting) to delay defoliation and the onset of dormancy and so increase foodreservesmayassistwintersurvivalalthoughresponsestophotoperioddifferwidelybetweenspecies.Somespeciesareknowntoberesponsiveinthattheonset of dormancy is prevented or delayed by short night-break lighting treatments (detailed by Vince-Prue, 1975)andsotheoverwinteringsurvivalofsuchsubjectsmaybeimprovedbyusingthistechnique.Suchspecies include Acer ginnala, Acer palmatum, Betula lutea, Betula pubescens, Cercidiphyllum japonicum, Diospyros virginiana, Hibiscus syriacus, Pinus taeda, Pinus ponderosa, Platanus occidentalis, Populus tacamahaca, Pseudotsuga taxifolia, Rhus typhina, Taxus cuspidata, Tsuga canadensis and Weigela florida.TherearesomeHNSsubjectswherethistypeoftreatmentisdetrimental;night-breaklightingwasshowntobeacauseofdeathintreeswherecontinuedgrowthpreventedwoodfrommaturing(Kramer,1937).SimilarresultshavebeenobservedwithshrubbyHNSspecies,notably Cotoneaster dammeri‘Skogholm’.

Aspects of liner productionOften, propagation and liner production are managed as separate entities yet they are very much interrelated and should be integrated as much as possible forbestresults.Whathappensatthefirststagehasconsequencesonthenextstage.Theuseofgood quality cutting material, for example, and its managementduringandfollowingrootingstronglyinfluenceslinerqualityandbusinessprofitability.

Managing rooted cuttings for quality liner productionAHDBHorticultureprojectHNS27:Propagation: stock plant and cutting processes influencing subsequent plant quality, aimed to develop guidelines for the managementofrootedcuttings,whichenabledgrowerstoincreaseprofitabilitybyimprovinglinerqualityandshorteningproductiontimes.Theworkestablishedsome important guiding principles for the successful transitionofnewlyrootedcuttingstoaqualitylinerandontoafinishedplant.Whilethestudiesfocusedon Cotinus,comparisonsweremadewithotherHNSspecies (such as Acer palmatum ‘Aureum’) to provide ausefulandbroadercontrast.Propagation should be done as early as possible in the season to enable strong root systems to developpriortowinter.Extendingthegrowingseasonunder glass (and the use of supplementary lighting) to delay dormancy and defoliation, and so help increase overwinteringfoodreserves,maycompensateforlatepropagationtoanextentandaidoverwintering.Whenpreparingcuttings.Retainingasmanyoftheoriginal leaves as possible and restricting any initial plantshapingtoapromptpinchingofnewshoots,ratherthanharderpruningpriortowinter,willalsoimprovesurvivalrates.Very supportive rooting environments, such as fog orclosedmist,forexample,shouldbeusedwherenecessarytoachievegoodrootingasthiswillhelpreduceweaninglossesduetoquickerandbetterrootdevelopment.Weaningshouldalsoberapidbutprogressive, for example, a short period of high humidity withoutleafwetting,underapolythenetent,sothatnormalgrowthisresumedasquicklyaspossiblewhileminimisinglosses.SeveralimportantprinciplesemergedfromHNS27thatcan be used to guide nursery practice for the successful transitionofnewlyrootedcuttingstolinerswithmanydifficultsubjects.Theseinclude:

• Propagation environment: use of a highly supportive rootingenvironmentsuchaswetfogorclosed mist,particularlyforsoftwoodcuttingstakenearly in the season, helps to promote strong and rapid root development

• Leaves on cuttings: retaining the original leaves on cuttings,wherepractical,assiststhesurvivalandestablishmentofcuttings.Eventhoseleavesthatappeartobeinpoorconditionfollowingalengthyperiodofwettingduringrootingareusuallyabletophotosynthesise.ThisalsosavespreparationtimeandmanyHNSsubjectsrootwellwithouttheneed to remove leaves

• Shootgrowth:rootedmaterialshouldbeweanedin atimelyandprogressivemanner.Newshootsthatdevelopduringrootingandweaningoftenfailtosurvive and so are of minimal value yet are net consumersoffoodreserves;rapidweaninghelps to minimise this problem

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• Root disturbance: root disturbance should be kept to a minimum, ideally using plug trays to root cuttingsordirectstickingwherespaceallows.Wherematerial is rooted in standard trays (and so more liabletorootcheck),ensureitisthoroughlyweanedwellinadvanceoffinaltransfertothegrowingonenvironmentinordertoreducewaterstress

• Weaning environments: in general, high humidity environmentswithlimitedshadeachievehighersurvivalratesthandrierenvironmentswithextrashade, although temperatures should not be so highthattheyencouragesoftnewgrowth.Usemist(orapolythene/fleecetent)forweaningbutensurethemistiswellcontrolledandgraduallyreducedtoenable a smooth transition from the higher humidity rooting environment

• Timeframes:thetimeframesallowedforrooting andweaningareimportant,ingeneral,itisbetter to extend the rooting period to achieve good root developmentandthenrestricttheweaningperiod(toabout7–10days).Withsubjectswhoseleavesusuallydeteriorate before full rooting is achieved (such as Acer palmatum, Cotinus, Euphorbia, Lavandula, Rosmarinus and Senecio), aim for an earlier transition to a drier but still supportive environment

• Spacing during establishment: rooted cuttings shouldnotbecomeovercrowdedoncetheyresumegrowthbecausetheaccumulationoffoodreservesanddevelopmentofwell-spacedbranchesisessential and depends on adequate illumination ofallleaves.Therefore,ensurerootedmaterialisadequately spaced

• Pruning:formanyHNSsubjects,pruningisessentialto create the best possible shape but ill-timed or over zealous pruning can be counter-productive andjeopardisewintersurvivalwhendoneintheextremeoncertainsubjects.Asageneralguide,rooted cuttings of less vigorous subjects (including Cotinus, Corylus, Magnolia, Rhododendron (some) and Syringa)shouldbeallowedtogrowreasonablyfreelyduringthefirstyeartoenablefoodreserves to be accumulated in the form of strong stems and rootsystems,whichaidoverwinteringsurvivalandprovide a sound basis for pruning early in the second year.However,manyquickgrowingHNSspeciesdorespond positively to summer pinching or trimming (including Choisya, Ceanothus, Forsythia, Hydrangea, Hypericum, Lonicera nitida, Philadelphus, Photinia, Senecio, Spiraea and Weigela)

• Propagationtiming;inHNS27,plantqualityafteroneyearinacontainercorrelatedbetterwithstemdiameter than any other measure of liner quality, underlining the need for early propagation and to buildupfoodreservespost-rooting.AlthoughmanyHNSsubjectscanbereadilyrootedthroughoutthelate spring to summer period, early insertion and rootinggivesaclearbenefitintermsoflinerqualityas it provides the longest possible time frame for rooted cuttings to accumulate food reserves

The disadvantage of late propagation (it is often unavoidable) can be partly mitigated by using heated glassandsupplementarylightingtoextendthegrowingseason, although this is only likely to be economic for highvaluesubjectsanditcanbedifficulttohardenoffsuchmaterial,necessitatingtheprovisionofsomedegreeofwinterprotection.

Managing disease incidence on overwintered HNS linersHigh relative humidity is common in unheated polythene tunnelsduringthewinterperiodandthiscanproduceenvironments conducive to the development of leaf diseases such as Botrytis anddownymildew.AHDBHorticultureprojectHNS49/49a:Influence of humidity and other stress factors on plant growth, underlined the importance of maintaining good environmental controlwithprotectedHNS,particularlywithinpolythenetunnels and especially for crops susceptible to leaf diseases like Botrytis anddownymildew.Theworkhighlightedtheneedtocombinegoodculturalmanagement,suchasgrowingonlowlevelirrigatedsand beds rather than overhead irrigated gravel beds, witheffective,balancedfungicideprogrammesstartedearly in the life of the crop, in order to produce top qualityplants.Keepingrelativehumidityintunnelcropsbelow80%reducedlevelsofdiseasesfavouredby highhumidity.

Capillary sand beds improve liner quality by keeping foliage dry and clean, so reducing disease incidence

Cropsshouldbeventilatedasconditionsallow,eveninwinter,toboosttheairmovementaroundlinercropsand susceptible crops should not be irrigated overnight whenfoliagewilltakelongertodry,soexacerbatingdiseaserisks.Cropsshouldalsobespacedastheydeveloptoenablegoodairmovementbetweenplants,sohelpingtodryfoliageandreducediseaseincidence.

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Integrating propagation and liner production – the ‘designer liner’ conceptIn nursery situations, it is far better to combine propagationwithlinerproductionandmanagethemtogether rather than separately to achieve quality productioninacost-effectivemannerandwith minimumwaste.AHDBHorticultureprojectHNS69:Ornamental shrubs: Developing the concept of the ‘designer liner’, aimed to develop a more integrated approach to growingliners,establishingtherequirementsforshapeandsizeatthestartandrefiningtheproductionprocesstoachievethisefficientlyandeffectively.Thisistheessentialprincipleofthe‘designerliner’.Theworkinvestigatedtheeffectsofstockplantpruning,use of pre-branched cuttings, the size and spacing of cuttings, the rooting environment, pot size, nutrition during rooting and establishment, and pruning or pinchingfollowingrooting,usingasmallnumberofHNSspeciesrepresentingdifferentplanttypes.Theevaluationofpre-branchedcuttingswasbasedon theviewthattheyaremoreabletodevelopand supportnewlateralsthanyoung,rootedcuttings.For many of the species tested (including Cotinus, Forsythia, Garrya, Magnolia and Photinia) the use of pre-branched cuttings enabled the rapid production of an established quality liner compared to liners derived fromapicalstemcuttings.Insomeofthetreatments,rooting a large pre-branched cutting resulted in the formation of an almost ‘instant’ liner, ready for potting intoa2or3-litrepotassoonasithadbeenweaned.Largercuttingswerenomoredifficulttoroot (providedtheywereplacedinasupportiveenvironment)and rooting in some species, such as Cotinus, occurred fasterwhentherewereanumberofactivelygrowingshootspresentonthecutting.

Theuseofpre-branchedcuttingswithsubjectssuchasPhotinia enable the rapid production of established, quality liners

The ability to form pre-branched cuttings on stock plant hedgeswillvarywithspecies(Syringa, for example, islessproductiveinthisrespect).Theoptimumenvironmentforrootedpre-branchedcuttingswill alsovarywithspecies.Forexample,ahighhumidity fogsystemwillbenecessarytosupportcuttingsof

relativelydifficult-to-rootspeciessuchasCotinus and Magnolia but large (20–25 cm high) pre-branched cuttings of Forsythia and Weigela should root readily underalowerhumiditymist.ThebestresultsinHNS69weregenerally associatedwithdirectstickingcuttingsinto9cmor1-litrepots,althoughitwasfeasibletoproducetheeasiersubjectsinplugtrays.Theadvantageassociatedwithpotsrelatedtokeepingthecuttingsstableduringpropagationratherthanarequirementformorespace.Forexample,resultswithCotinus suggest that spacing duringpropagationandoverwinteringhadlittleimpactonsubsequentgrowthandpre-branchedcuttings could be produced at the same spacing as direct stuckconventionalcuttings.Althoughthemostimpressiveresultsinthisworkwereoftenassociatedwithpre-branchedcuttings,qualityliners could also be obtained from conventional apical cuttings by optimising other factors, such as enhancing thenutrientstatuswithincuttingsasearlyaspossible.The addition of nutrition to Magnolia cuttings early in the productioncycleenhancedgrowthandlateralformation.Inanumberofcases,whenplantswerebeingpropagatedbyconventionalapicalcuttings,itwasfound that a single pruning treatment implemented shortlyafterbud-breakinthesecondyearwasaseffectiveormoreso,thanearlierpruningorpinching.GoodplantsizeandshapewereobtainedinMagnolia and Photinia by single pruning treatments in March, followingbudbreak.

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International Plant Propagators’ Society

The International Plant Propagators’ Society (IPPS) is an international association of plant production professionalswhoseprimarymissionistoadvancetheartandscienceofgrowingplantsandtodisseminateknowledgethroughouttheglobalcommunityfrom and to those engaged in plant production for the benefitofall.Membershipincludesthosewithaninterestinornamental horticulture, vegetable and fruit plant production,floriculture,silviculture,plantationcropproduction,amenityhorticultureandallotherfieldsrelatedtotheproductionofplantsforpublicuse.ThemissionofIPPS,withafocusontheglobalcommunity of those involved in horticultural plant production, is to:

• Shareknowledge,informationandskills

• Provide guidance and support for lifelong career achievements

• Increase recognition of the profession

• Maximise the integration of research, education and horticulturalknowledge

For further information, visit ipps.org ThefollowingfivepapersarereproducedcourtesyoftheIPPS from various proceedings and publications over severalyears.

Cracking Photinia

Geoff De La Cour-Baker, Manager, Palmstead Nurseries LtdAchieving commercially viable rooting of Photinia ‘RedRobin’cuttingshadalwaysbeenaproblem forusand,sofaraswecouldseeatthetime(2006), norealtrialshadbeenattemptedwiththissubject.WedecidedthereforethatitwouldbeaworthwhileandenjoyableIPPSproject,toexplorewaysofgettingourPhotinia cuttingstorootbetter.Itwasalsohopedthattheprojectwouldbroadenourpropagationknowledge and understanding, and act as an introduction to theuseofrootinghormones.Tobeginwith,weneededtounderstandthepropagationproblems being experienced, including rotting and excessivecallusformation,inordertofindasolution. Ourefforts,therefore,focusedonfindingtheoptimumtype of cutting, rooting environment, hormone treatment (ifrequired)andtimeofyearforpropagation.Wealsobenchgraftedseveralplantsinwintertoseeifthiswasabetterapproach.

Throughourexperiencewithrootingothersubjects,wedecidedthatnodaltipcuttings(8cminlength,nowounding)wouldbethebeststartingpoint.Wethenexploredtakingdifferenttypesofcuttingmaterialatvariousstagesoftheyear:softwood(redtipped)inMay,greenwood/semi-ripe(redstem)inAugustandNovemberandevergreenhardwoodcuttingsduringFebruary.Inallcases,theleavesofthecuttingswerereducedtopreventoverlapwithinthetraysandthecuttingswereinsertedintoapeat-basedrootingmedium.Norootinghormoneswereusedinthisinitialstudy.Thetrayswerethenplacedinthreedifferentrootingenvironments:afoggingunit,amistbedandundercontactpolythene.Baseheat(18–21°C)wasusedbetweenNovemberandApril.Eachtrialconsistedoffourx54plugtrays.Cuttingswerethenmonitoredforsignsofcallusformation,rooting,leaf-drop,rottingoffandgeneralhealthstatus.Theresultsfromthefirsttrial(cuttingsandrootingenvironments)weredisappointingandarepresentedinFigure8.Followingthisinitialstudy,weturnedourattentiontothe use of rooting hormones in an attempt to increase therootingpercentage.Thehormonesweselectedwerebased purely on availability and recommendation, as werethestrengthsatwhichwemixedandappliedthem.We also tested one theory of using an aspirin solution to rootcuttings.

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Figure8.Photinia:typesofcuttingsanddifferentrootingenvironments

ThehormonetrialstookplaceinNovemberusing semi-ripecuttings(nowounding)underfogwithbaseheat(18–21°C)andtheseproducednoticeablybetterresultsbyFebruaryofthenextyear.Thetreatmentsusedwere:Synergol(liquid‘quickdip’at5,000ppmand 3,000 ppm IBA), Seradix 3 (talc at 8,000 ppm IBA) combinedwithliquidacetoneandanaspirinsolution(fourtabletsx300mgto200mlofwater).WiththeSeradixtreatment,thecuttingswerefirstdippedintothe acetone for three seconds and then the hormone powder,theideabeingtousetheacetoneto‘extract’

International Plant Propagators’ Society case studies

International Plant Propagators’ Society case studies 123

theIBAwithinthehormonepowderandimproveabsorptionofthehormonebythecutting.The application of rooting hormones dramatically increased rooting percentage, most notably the Seradix 3+acetonedip.TheresultsaresummarisedinFigure9.

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Figure9.Photinia:Comparisonofdifferentrootinghormonetreatments

In the Figure 9, key stock material refers to cuttings takenfromfield-grownstockplantsandcontainermaterialwasthattakenfromcontainer-grownmotherplants.Alltreatmentswereappliedasfive-second‘quickdips’tothebaseofcuttings(exceptSeradix3,wherecuttingbasesweredippedinacetoneforthreesecondsandthenthepowder).We used the results from the hormone trial and applied its principle to a large batch of Photinia, taking cuttings from stock in August and October and successfully produced rooting percentages of 92%, a major improvementontheoriginaltrial.Theseplantswerestrongandhealthywithgoodrootsystemsand,afterashortperiod,werepottedonintothelinerstage.Thenursery requires over 10,000 rooted cuttings of Photinia ‘RedRobin’ayear,soourtrialresultswereagreatsuccessforusandarealbreakthroughforthenursery.Asacomparisonwithcuttings,wealsosidegraftedscion material of Photinia ‘Red Robin’ onto Photinia davidianarootstocks(2-litrepots)duringFebruary.However,theresultsweredisappointingand,forus, thisapproachwasnotacost-effectiveortime-savingmeans of producing large batches of Photinia ‘Red Robin’ (although the small number of successful graftsdidgrowontomakegoodhealthyplants).

Hibiscus grafting Mark Howard, Nursery Supervisor, John Woods Nurseries LtdHibiscus syriacus cultivars can be propagated by cuttingsorgrafting.Graftingproducesamuchstronger, saleable plant in less time than traditional

cuttingsand,becausethewoodofHibiscus is quite soft,theyarerelativelyeasytograft.Theyareagoodplantforanybodynewtograftingtopracticeonwithareasonablelevelofsuccess.Hereishowtodoit.

• Graftinthedormantseason,usuallyJanuary or February

• Use one-year-old Hibiscus syriacus seedlings that are approximately 8–10 mm in stem diameter

• Scionwoodcancomefromspeciallygrownstockplants that need to be cut back hard in the spring to give strong healthy one-year-old material for grafting thefollowingwinter.Alternatively,scionwoodcancomefromplantsgrowninproductionthatneedpruningback.Collectmaterialthatisatleast 4–6mmindiameterandisfirm,sothatitdoesn’tbend too easily

• Preparethescionsasyouwouldahardwoodcuttingwithaslopingcutatthetopjustaboveabudandapproximately15–18cminlength.Thereisnoneedforabudatthebottom.Placetheminasealedpolythene bag in the cool until required for grafting

• Prepare the rootstocks by trimming the roots and removingallthetopgrowthjustabovethehypocotyl,(thisistheareajustabovewheretherootsstarttogrowandtheareawhereyouwillmaketherootstockincision).Cleanthisareatoremoveanysoilandavoidtheriskofcontamination.Graftinglowdownlikethiswillreducesuckering

• There are three types of graft that can be used dependingonthesizeofthescion.Ifthe rootstock and scion are of similar thickness, then astraightforwardwhipgraftcanbeused.If,asisusually the case, the scions are smaller than the rootstock then you can use a side graft, matching thecambiumsaccordingly.Asthecambiallayerissometimes quite deep in a Hibiscus, often the most suitablegrafttouseisarindgraft.Thisensures goodcambialcontactwithouthavingtocuttoodeeplytoexposethecambium,aswithasidegraft

Grafting produces a much stronger, saleable plant in less time than cuttings

124 International Plant Propagators’ Society case studies

• Use150mmby3mmwhiteflexi-bands(biodegradable rubber) for tying the graft together, thesewilldegradesoonerthanothertypesand won’tcutintothesoftwood

• Dipthewholegraftintograftingwaxatatemperatureof70°C,therebysealingeverythingexcepttheroots

• Plungethegraftsintodeepblackcratesfilledwithageneral potting medium, ensuring the roots are covered but not the scions and place these crates in an environment that gives an air temperature range of5–15°C

• Callusingandsubsequenttopgrowthwilltakeplacewithinfourtosixweeks,atwhichpointtheycanbemovedtocooler,frost-freeconditions.Oncetopgrowthhasstarted,thenthegraftswillneedliningout or potting up

• Good,strong,well-shapedplantswillcomefromthosethatareplantedinwell-drainedopengroundforaperiodofonetotwoyears

• Runahedgetrimmeroverthemregularlywhen thegrowthissofttoencourageprolificbranching

• Themainpesttowatchoutforisaphid,otherwiseHibiscusarerelativelypestanddiseasefree.Yellowgrowthinthespringisusuallyonlytemporaryandinvariablyduetocoolnightswhilethetopsareactivelygrowingbuttherootsarenotyetinfullgrowth.Foliarfeedingwillhelp,especiallyincontainer-growncrops

Lavender propagation – rooting rottersDavid Hide, Technical Manager, Walberton NurseryLavandula can be propagated from seed, cuttings and layeringbutwhenlargebatchesofidenticalplantsofa named cultivar are required, cuttings are the most commonmethod.However,theyareaseasytorotastheyaretoroot!Hereisabriefoverviewofhowtopropagatethemfromsoftwoodandsemi-ripecuttings,based on our experiences of raising young plants here atWalbertonNursery.Softwood cuttingsAtWalberton,werootupto100,000softwoodtipcuttingseachyearbetweenJanuaryandJune.

• Uniformcuttingsaretakenfrompurposegrown one-year-old 3-litre stock plants under (frost) protection.Theseyieldbetween50–100cuttings everyfourtosixweeks,oncethefirstflushofgrowthhasbeencut,whichisusuallyinMarchandApril

• Cutting length varies and is both species and cultivar dependent;Lavandula dentata ‘Dusky Maiden’ may be6cm,whileLavandula angustifolia ‘Hidcote’ may only be 3 cm in length

• Consider cleaning up stock via micropropagation toretainvigour.Thisissomethingwedoeveryfouryears for many of our lavenders

Stockplantsaregrowntoprovidethenurserywithtimelysuppliesof high-quality, uniform cuttings in the required quantities

• All cuttings are internodal tips and all preparation is done at collection, using ‘snips’ (small scissors) to makeacleancutjustaboveanode.Thisproduces a bare section of stem that is inserted up to the next pair of leaves

InternodalsoftwoodtipcuttingsarerootedusingdibbledPreforma trays

• Byseparatingthecollectingfromthestickingweareabletomonitoreachpartoftheoperation.Wefeelthisallowsustodevelopmorefocustoeachoperation and has helped, in particular, to increase ourstickingrates,whichin2012averaged500cuttingsperpersonperhour.Weonlymaketipcuttings because, although stem sections root okay, theyalsorotmoreeasilyandsometimesfailtogrowaway,eveniftheyarewellrooted

• Nofurtherpreparationisrequiredorrooting hormone used


• WeinsertallofourlavendersintoPreformaJiffy126s(ready-to-useplugtrays),whicharecentrallydibbled.Thisprovidesuswithsomethingto‘aimat’andsoremovesanyindecisionatpointofinsertion(whichalsospeedsupthestickingprocess).Softwoodtipcuttings are easier to insert into a dibbled tray and sothereislessbruisingofthesoftstem,witharesultant reduction of Botrytis enteringatthispoint.This had been a major cause of losses prior to us using dibbled trays

• All rooting takes place under milky Thermaprop polythenefilmtents,withabasalheatof20°C

• Rootingtakesbetween14–21daysbutitwillbe a further seven days before the cuttings are fullyweaned

• Wewouldexpectrootingpercentagestobeinthe high nineties

Cuttingsarerooted(14–21days)underpolythenewithbaseheat(20°C)thenweaned(sevendays)

Semi-ripe cuttings• Select 6–8 cm long semi-ripe cuttings from

non-floweringshootsinAugustandSeptember

• Insert into a free draining propagation medium and placeinalowhumidityrootingenvironmentsuch as a cloche or unheated polythene tent

• RootingwilltakeplacewithineightweeksThistechniquewasforalongtimetheindustrystandardbuthassincebeensupersededbytheuseofsoftwoodcuttings.Key elements to success with lavenders• Have access to good quality stock and understand

the rooting requirements of a lavender

• Softwoodtipcuttingsrootquicklyinhighhumidityenvironments but the Thermaprop polythene reduces foliagemoisture,whichlavenderdislikes.Verylittlecondensation forms on the polythene, thus reducing theriskofdrips,foliagewettingandBotrytis.Lavender is very prone to fungal diseases and resent sittingfortoolongwithwetfoliageorwaterloggedrootzonesandisthereasonwhyweusebothThermaprop polythene and Preforma plugs

• Monitor the crop daily and react to the changing weathertomaintaintheoptimumrootingenvironment

• Water in the morning only and on dull days, consider venting the ends of tunnels even before rooting has commenced.Thiswillreducethetimethatthecuttingssitwithwetfoliage

• Weapplyaweeklyfungicideprogramme;I’mnotsurethisisentirelynecessarybutwedoitforgoodmeasure

• Once rooting commences, reduce humidity levels byfirstopeningtheendofthetunnels.Replace withafleecetentwithinaweektocompletethe weaningprocess

• Softwoodtipcuttingsgrowawayquicklyanditispossibletoassesswhentherootingandweaningprocesses are complete, as cuttings that still require higherhumidityenvironmentswillquicklywiltifleftunprotected

• Don’tbeafraidtore-coverwithfleeceorpolytheneat this point

Well-rootedcuttings,fullyweanedandreadyforpotting

Rhododendron and Azalea propagation at Millais NurseriesDavid Millais, Millais NurseriesMillaisNurseriesisaspecialistRhododendron nursery producing about 35,000 plants per year for sale throughout Europe to private gardeners, parks, landscapersandgardencentres.Sizesrangefromdwarfsin3-litrepotsuptospecimensin150-litrepots.Wehaveoneofthelargestrangesintheworld,growingmorethan800differentvarietiesbutrarervarietiesareonlypropagatedeverytwotothreeyearstosimplifyproduction.


• Propagation methods: our main propagation method isbycuttingsbutwemakeuseofautumngraftingfordifficult-to-rootsubjectsandseedforsomeofthewildcollectedspecies.Wealsobuymicropropagatedlinersofotherdifficult-to-roottypesofRhododendron butourexperiencehasshownthattheydonotalwaysmakesuccessfulplants.Micropropagationisverysuccessfulwithsomevarietiesbutonotherssuch as Rhododendron ‘Crest’, characteristics such asflowersize,colourorhabitcanbealteredfromtheoriginalclone.Frustratingly,wehavealsoexperiencedweakplantsthatsnapoffatthebaseafterthreeyearsduetotweezerdamagewhilehandlingthecotyledonin the laboratory

• Facilities: our propagation glasshouse has aluminium rollerbencheswithThermabedhotwaterheating.Each bench has individual controls for temperature andmist,allowingflexibilityandenablingheatsavingstobemade.Withslow-rootingsubjectssuchas Rhododendron, the ability to pick over the crop at waistheighthasprovedinvaluableovertheyears Thebenchesarecoveredwithcapillarymattingand toaiddrainagewehavesmall‘tails’ofmatting droppingbelowthebenches,whichhelptosuckoutexcessmoisture.Ontopofthematting,wehaveperforated black polythene that is easy to brush downandkeepclean.Thebencheshavemetalhoopsoverthetop,whichsupportthemistlinesandcreateapolythenetenttogivegoodhumidity.Atleastonceperyearwestripoutallthemistnozzles,filtersandanti-dripvalvesandsoaktheminvinegarovernighttoremovelimescaledeposits.ThebenchesandcapillarymattingarecleanedusingJet5andallthe automatic controls are checked for operation

Azalea and Rhododendron cuttings are rooted under polythene withmistandbaseheatduringthespringandsummerperiods

• Timing:ourcuttingsseasonstartsinlateMaywithdeciduous Azalea.Wefindthatmostofthesewillrootquiteeasilybutwestillhavedifficultieskeeping

themalivethroughthewinterandmakingthembreakintogrowthinspring.Ourobjectiveistorootthemasearlyaspossiblesothatwehavealargewell-rootedplugintimeforwinter.Wehavetriedkeepingthemcoldtopreservesugarlevelsduringthewinterandkeepingthemgrowingandwarmforlongerinthewinterbutwestillsufferlossesduringthefirstwinterortwo

• Our cuttings season then moves onto Rhododendron species,whichweliketotakebyearlyJuly,followedby compact species, Rhododendron yakushimanum, dwarfsandevergreenAzalea types.Recently,wehave been shifting hybrid propagation from autumn toearlysummerwithgoodresultsbuttheydotakeupalotofspaceonthebenches.DuetopoorresultswithcuttingstakeninthereallyhotweatherofAugust,wetrytotakethemeitherbeforeorafteranyheatwave.RootingcanbeasshortasfourweeksforAzaleaandaslongassixmonthsfordifficulttypes of Rhododendron

• Stockplantsandcollectingcuttings:weliketocollectcuttingmaterialfreshfromourownstockplantswherepossiblebutwealsomakeuseofpruningsfromourlinercrop.Wetrytocollectearlyinthemorningwhenthecuttingsaremoreturgidbuthavefound that turgidity can be increased by refrigerating in a moist polythene bag overnight if needed

• Leaf trimming of cuttings: many people advise against trimming leaves due to the risk of disease entrythroughthewoundbutwehavealwaysfound itbeneficialinreducingtranspirationandpreventingdiseasespreadthroughoverlappingwetleavesin|thetray.OnsmallleavedRhododendronwedonottrimbutonhybridswithleavesmorethan50mmlongwe,typically,reducethesizeoftheleafbyhalf.Since rhododendrons do not like to be disturbed at pottingtime,werootincellsofeither40mmor50mmdependinguponsubject.ThegrowingmediumusedisBalticpeatwithgoodaerationanddrainageandwenormallysetthebasetemperatureat17°C

• Woundingandrootinghormones:dwarfRhododendron and Azalea are quite easy to root and thesearenormallydonewithoutanywoundingatthebasebutonhybridrhododendronsweusuallywoundthebottom15mmofstemdowntothecambiumlayertoaiduptakeofhormone.Historically,we’vemainlyusedapowderformulation(0.3%IBA)butsometimesswitchedtoaweakerconcentrationearlyintheseasonoronwhitefloweredAzalea cultivars, whicharepronetoscorch.Laterintheseason,hardercuttingsandmoredifficultrootingplantssometimes need stronger hormones but there is a finelinebetweenabeneficialhormoneandonethatscorchesthecutting.Wefoundliquidhormones(suchasSynergolwhenitwasavailable)allowedgreaterfine-tuningofstrengthandwearecurrentlybuildingexperiencewiththenewhormoneproductsavailable to us


• Rooting environment: during the summer months, wetypicallyusemistunderneathclosed‘milky’whitethin grade polythene plus additional shading on the outsideoftheglasshouse.Inadditiontotheregularwetleafmist,wehaveaddedatimeclockforrestricting the mist in the morning and evening turningitoffatnighttotrytokeepthecuttingsdrier.FollowingthesuccessofAHDBHorticulturetrials,weare currently trying out Evaposensor controls, again toreducewaterapplication.DuringSeptember,werestrictthemiststillfurtherandaimtoturnitoffcompletelybytheendofthemonth.Bythen,lightlevelsandtemperaturesarefallingandwecanmaintain good humidity by just relying on closed clearpolythenethroughthewinterandtheoccasionalburstofmist.Duringthewinter,wetypicallyventeachtentforanhourorso,twotothreetimes perweek

• Cropprotection:duringpropagationwedonotusemany fungicides on the cuttings but regularly spray overwithcompostteaandproductssuchasRevive,SBPlantInvigoratorandseaweedfeeds

• Records:wehavethebenefitofmyfather’spropagation records going back more than 30 years showingtimingsandhormoneusedforeachvariety.However,aseachseasonisdifferenttherecordscanonlybeaguidesoweuseexperiencetotelluswhena shoot is ripe for taking

• Newideas:propagationisalonglearningcurve and organisations such as the IPPS help spread knowledge.Sometimes,avisittoanothernurserygivesyouanideatotry,whichmayormaynothelpyoursituation.Everypropagationhouseisdifferentandourworstyearforcuttingsuccesswaswhenwebuiltournewhouseandeverythingchanged!Itisworthtryingnewtechniquesbutdon’tchangetoomuch at once

Success with Hebe cuttingsKarl O’Neill, Propagation Manager, Bransford Webbs Plant CompanyAtBransfordWebbs,wegrowapproximately180,000Hebe plants, the vast majority of these being the compact, small leaf varieties such as ‘Pink Pixie’, ‘Margret’and‘Pascal’thatwesupplytogardencentresinthespring.Wegrowalimitednumberofthelargerleafvarieties,whicharepropagatedinaverysimilarwaybutwithalongerproductioncycle.Ouraimistoproduceaclean,compact,well-branched2-litreplantformarketfromFebruaryonwards.One of the major factors in successful Hebe propagation is the quality of the stock plants and, in turn,thecuttingmaterialtheyproduce.Hebe is relatively easytoroot,however,thejuvenilityandcleanlinessofthestockmaterialwilldictatethequalityandvigouroftherootedcutting.Juvenile,currentseason’sgrowthwillrootreadilyandgrowawayvigorously,enablingearlytrimmingopportunitiesandsoawell-branchedplant.

NoneofourcuttingmaterialistakenfromtraditionallygrownstockplantsaswefeelthisisnotidealforHebe, whichissusceptibletoanumberoffoliardiseasesandneedstobekeptyoungandactivelygrowing.Instead,wegrowallourstockplantsalongsidethecurrentseason’s saleable crop, meaning that they receive the same(ideal)culturalandfungicidaltreatments,whichhelpproducetheclean,juvenilegrowthwerequire.Infact, the stock plants are used once and then destroyed orgrownontomakealatersaleablebatch.Cuttings are taken in the autumn from stock plants that have been potted three months previous and have had theirfirstflushofjuvenilegrowth.Stemtipcuttingsaretakenapproximately20–40mmlong,withtheleavesremovedfromthelowerhalf.Norootinghormoneisused,asthisisnotnecessarywhenrootingHebe;italsoaddslabourandchemicalcostsandhasbeenshowntodamagesomevarieties.

Plug for liner potting

The cuttings are struck in a preformed plug media, containing a peat, perlite, bark and vermiculite mix, withaddedcoir(20%)forstructureanddrainageoverthewintermonths.Themediacontainsbothbaseandcontrolledreleasefertilisers.Amistsystemwithbaseheat(18°C)andautomaticshadingisusedtorootthecuttings.Therootingenvironmentiscomputercontrolled and is governed by a solar radiation sensor andthermostaticprobes.


Themajorityofthevarietiesrootintwotothreeweeks,withthemistbeingreducedbyapproximatelyhalfafterthesecondweekandthenreducedfurthereachweekuntilrooted.Theyarethenweanedinsituforonetotwoweeksandmovedoutintoacolder(frost-free)andlesshumidenvironmenttohardenoff.Thisalsohelpsto slowdownthesoftflushofgrowththeyputonintherootingenvironment.Therootedcuttingsareoverwinteredinacoldglasshouse,wheretheycontinuetogrowslowlybut canextendto60–80mm.Inlatewinter,theyare machine-trimmed to approximately 20 mm to encourage breaks.Then,sixtotenweeksaftertrimming,theyarepottedonintoa9cmlinerpotandgrownonsandbeds.Theyarethenpottedintotheirsaleable2-litrepotsfivetosixmonthslater.

Attention to detail and good cultural practice produces uniform batches of clean looking good stock ready for sale

Allthewaythroughtheproductioncycle,ourHebe crops are subjected to a rigorous fungicide programme, protectingagainstdownymildew,powderymildew, leaf-spots, Botrytis and Fusarium.Withanevergreencrop like Hebe,preventionisdefinitelybetterthancure.


Propagation managementThissectionsummarisesthecurrentknowledgegapsin the propagation process and suggests appropriate researchorknowledgetransfertoaddressthem.

Stock plant and cutting nutritionLittledetailedworkappearstohavebeendoneor,atleast published, on the nutritional requirements of stock plants to sustain their production of uniform, high-qualitypropagationmaterialorontheeffectsconferred by supplementary feeding stock plants on thesubsequentrootingpotentialofcuttings.Researchis needed to address this, examining the use of liquid andfoliarfeeds,compostteas,etc.

Cold storage of leafy cuttingsWhiletheAHDBHorticulturegrowerguideHNS Cold storage – How to successfully cold store hardy nursery stock,helpedaddresscurrentknowledgegapsonhowtogetthebestfromcoldstorage,researchisneeded to provide a better understanding of the cold storage requirements of leafy cuttings and, in turn, enablethedevelopmentofmorespecificguidelinesforoptimum storage times, temperatures and conditions forarangeofHNSsubjects.Suchinformationwouldhelpenablegrowerstocoldstorecuttingstooptimumeffectandfurtherexploitthebenefitsofcontrolledtemperaturestorageasapropagationmanagementandschedulingtool.Theuseofcoolboxestoremove‘fieldheat’whencollectingsoft and semi-ripe cuttings should also be considered as a simple and cheap means of maintaining freshness beforepropagationofsmallquantitiesofmaterial.

Lean management and its application to propagation workLean management is a set of techniques that can be usedtohelpreducecostsandaddvaluetobusinesses.It can do this by improving productivity, reducing plant lossesandremovingwastage.SomepropagatorsappearunawareofthewiderbenefitsofleanandhowitsprinciplesandpracticescanbeappliedtoHNSpropagation.Knowledgetransfertailoredtotheneedsofpropagatorswouldbeusefultobuildconfidenceandraiseawarenessoftheconsiderable savings that may accrue from the use of leanmanagementinthepropagationprocess.

Wounding of cuttingsWounding cuttings increases the quantity and quality ofrootsasnewsitesforrootinitiationaretriggeredwhenbasalstemtissueisexposed.Itisaparticularlyusefultechniquetocoaxrootsfromdifficultor slow-rootingsubjects,especiallywherethewoodisquitelignified.Muchofthecurrentknowledgebaseisnotresearch-based.Newworkshouldconsiderand trialdifferentmethodsofwounding,linkedwiththeuseofhormonerootingaids.

Leaf removal from cuttingsAvoiding the need to remove or strip leaves from large numbersofcuttingssavesconsiderabletime.PastresearchtoinvestigateleafremovalwitharangeofspeciesfoundthatmanywoodyHNSsubjectsrootedbetterwhentheirlowerleaveswereretained(althoughHebecuttingsrootedbetterfollowingleafremoval).Whilethisworkhighlightedscopeforconsiderabletimeandsocostsavingsforgrowersbynotremovingleaves,furthertrialsworkwithawiderrangeofwoodyandherbaceous subjects is required to substantiate its initial findingsbeforefirmrecommendationscanbemade.

Rooting hormonesFollowingthecommercialwithdrawalofSeradixproducts and Synergol during 2011, the Dutch product Rhizopon (based on IBA and available as ready-to-use powdersorwatersolubletabletsdissolvedforuseasdipsorsprays)isnowthestandardproductapprovedfor use and a useful rooting guide to accompany the productrangeisavailabletogrowers.While‘quickdip’ratherthanpowderapplicationshavebeenshowntoimproverootinginsomedifficultHNSspecies,growersnolongerhaveeasyaccesstothehigherstrengthsrequiredtoachievehighrooting.Currently, there are no approved liquid rooting hormonesavailableforsaletotheUKmarketcontaininghighconcentrationsofIBA.TheonlyproductcontainingIBAthatcanbedissolvedinwateristheRhizoponAA 50mgwatersolubletabletandthemaximumconcentrationapprovedis1,500ppm.Newresearchtoevaluatedifferenthormones,formulations,timings,combinationsandratesforarangeofHNSsubjectswouldhelpgrowersoptimisetheiruseandidentifycurrentproductgaps.

Propagation techniquesImproving propagation of difficult-to-root subjectsWhilethemainpropagationtechniquesarewellunderstood,thereisscopefornewresearchtohelpimprove the propagation and economic production of difficult-to-rootsubjects(suchasvarietiesofCamellia, Daphne, Rhododendron and various herbaceous perennials including Acanthus, Euphorbia and Romneya), whichwouldenablebestpracticeguidelinestobedevelopedforgrowers.Newworkshouldincludestock plant management, propagation timing, seed treatments, rooting cuttings, peat-free rooting media, newrootinghormones,woundingtechniquesandrootingenvironments.

Physiology of rootingThereisaneedfornewworkonplantphysiologyduringpropagation,todevelopabetterunderstandingofwhysome plants propagate more readily from certain types ofcuttingsthanothersandataparticulartimeofyear.

Research and knowledge transfer requirements

130Researchandknowledgetransferrequirements

Why,forexample,aresomeHNSsubjectsslowerormoredifficulttorootthanothers?Whatarethe‘triggers’orrootingco-factorsinvolved?Suchworkwouldhavesignificantcommercialvalue,wereittocreateeasierandmoretimelyrootingprotocolsfordifficulttopropagatesubjectswhiledeliveringmoreflexiblepropagationperiodsforother,easier-to-rootplants.Newworkshouldalsoinvestigatethevegetativeversusfloraldichotomywithinherbaceoussubjectstohelpenable optimum timings to be established for successful rooting.

Preconditioning cutting materialNewworkonpreconditioningstockplantsshouldspecificallycovertheuseofdarknesstostimulaterootingofdifficultsubjectsandtheuseofartificiallightingduringpropagationtobuildonearlierworkaimedatimprovingtherootingabilityofcuttings.Thebenefitsofpreconditioningshootspriortocollectingcuttingsofdifficult-to-rootsubjectswerehighlightedbytheworkatNIABEMRbutthishasn’tprogressedbeyond the research stage, perhaps due to practical complications.However,withmorestockplantsnowgrownincontainers,oftenunderprotectionandsowithgreater environmental control, the process should be mucheasierandsimplertomechaniseandmanage.Theremayalsobeawiderroleforartificiallightingtoimprove the yield and timeliness of cutting production fromcontainer-grownstockplantstoaidpropagationschedulingandtherootingofcuttingspost-insertion.Lightingcanbeusedwithsuccesscommerciallytoimprovewinterrootingofherbaceousperennialsandsecureearlycuttingsfromstockplantsunderprotection.Whiletheconclusionsofpreviousworkwerethatlighting(particularlypost-insertion)wasunlikelytobeeconomic,itmaynowbetimelytoundertakenewtrialswithawiderrangeofHNSsubjectsaspartofabroaderprogrammeofresearchusingarangeofmoreefficientlamptypes.

Transport, storage and handling of cuttingsBothunrootedandrootedcuttingsarenowpurchasedfrom a range of suppliers and often from over long distances(sometimesoutsidetheUKandevenEurope)butlittleornoworkhasbeendonetoestablishoptimumstorage,handlingandtransportperiodsfordifferenttypesofmaterial,fromwhichbestpracticeguidelinescouldbedevelopedforgrowers.GiventheincreasingvolumesofcuttingsthatarenowoutsourcedbyUKgrowers,thereisapressingneedforbenchmarkingworkaroundwhichpracticalguidelinescouldbeestablished.

Health status of cuttingsThereisaneedtoenablegrowerstoundertaketheirowndiseasescreeningtests,forexample,usingreliableand rapid diagnostic tests to enable on-site checks for arangeoffungal,bacterialandviraldiseases.

Propagation environments and systemsWater managementStrikingtherightbalancebetweenadjustingmistlevelstoreducewaterlossfromleafycuttingswhileavoidingwaterloggingoftherootingmediumcanbedifficulttoachieve.Potentially,capillarysandbedsofferasolution,althoughcoveringthebedswithmembranestocontrolweeds,preventrootingthroughandtokeeppotscleanmay,however,impedegoodcapillarycontactandsodrainage.Capillarymattingisalsosometimesused andfurtherworkisneededtoevaluatewaysofimprovingdrainagefrombeds.Related to this is the nature of the rooting medium, typeofplugandtray,andhowtheymayaffect drainageofthemediaandpotentialrooting.Thereis a need, therefore, for research to compare rooting resultsofdifferentsystemsandfindpracticalwaysforgrowerstomeasuretheairandwatercontentofmediaacrossarangeofplugandmediatypes.

The role of the EvaposensorRelatedtowatermanagementundermist,systematiccomparisonsofdifferentmistregimestoidentifyoptimal set points for particular species and cultivars are needed to enable nurseries to get the best from the Evaposensormistcontrolequipment.

AftercareCrop protectionThere is interest in the use of various microbial products to aid preventative disease control, either incorporatedintothegrowingmediumorappliedasdrenchtreatments.Interestsofarhaslargelycentredon their use to control root and stem base fungal infectionsinspecificcrops.Suchproductslinkwell

Accurateon-sitetestsfordiseaseswouldspeedupdiagnosis and treatment

Researchandknowledgetransferrequirements131

withcurrentmovestowardsgreateruseofintegratedcropmanagementandmayhaveawiderroletoplayinpropagationsituations,wheretheyarerelativelysafe.Thereisaneedtoreviewandscreenarangeoftheseproductstoassesstheireffects.

Integrated pest managementThe higher temperature and humidity environments of propagation restrict the range of biological control agents and release methods that can be used in suchsituations.Itisoften,therefore,necessarytoadoptdifferenttacticswhenusingIPMinpropagationsituationsandnotallgrowersappreciatehowbesttodeviseandadjustprogrammesaccordingly.Thefrequentarrivalofnewproducts,bothbiological control agents and biopesticides, can also make it time-consumingtokeepuptodatewithinformation.Furtherknowledgetransferwouldbetimelytoprovidethisinformation.

Integrated crop managementAHDBHorticultureprojectHNS185:Understanding and managing crop protection through integrated crop management,foundthatmanygrowersareawareof integrated crop management and the implemention ofsuchmeasures.Thissuggeststhereshouldbelittledifficultyinmeetingatleastsomeoftherequirements oftheECSustainableUseDirective(SUD),which,aspartoftheDirective,necessitatesgrowerstoreduce the use of pesticides and demonstrate good practice by2014.However,thereisaneedforfurtherknowledgetransferon the more technical aspects of integrated crop management, such as the propagation of disease-free material, including the use of on-site diagnostic tests and their utilisation for the detection of latent infections inplantmaterial.

Liverwort and moss controlBothoftheseweedscontinuetoposeproblemstopropagatorsandthereisaneedtoreinforcethebenefitsof cultural control measures and good nursery hygiene linkedtotheuseofalternative,non-chemicalweedcontroloptions.AHDBHorticulturefactsheet25/12 Non-chemical weed control for container-grown hardy nursery stock, provides detailed guidance on non-chemicalweedcontrol.Furtherknowledgetransferthatraisesawarenessofalternativestochemicals,underlines the value of nursery hygiene and cultural weedcontrolmeasures,anddemonstratesapplicationequipmentwouldhelpreinforcebestpractice.There is also a limited number of pesticides that provide goodmossandliverwortcontrolandtheseshouldbescreenedwithaview,ifeffective,toappropriateapprovalsbeingsought.

Cold storage of rooted plugs and linersThe ability to hold rooted cuttings in modules and pot linersforshortperiodsuntilrequiredwasoneofseveralbenefitsidentifiedbyAHDBHorticultureprojectHNS113:The feasibility of using low temperature storage as a scheduling aid in nursery stock production, reducing theneedforsubsequentgrowthcontrolandenablingthedevelopmentofscheduledproductionprogrammes.Nopublishedworkappearstohavebeendonetodetermine more precisely the temperature requirements ofHNSspecieswhenstoredinthisway.While3–4°Cislikely to be a good starting point and is used for bedding plants,researchisneededtodevelopamorespecificunderstandingofHNSrequirements,whichwouldenablefirmerguidelinestobedevelopedforgrowers to exploit cold storage for scheduling purposes in numerousways.Table 27 summarises the current research and knowledgetransferrequirements.

Granulatedcorkasamulch(left)usedtosuppressliverwortatpropagation

ColdstorescouldbebetterutilisedtoscheduleHNSproduction

132Researchandknowledgetransferrequirements

Table27.Currentresearchandknowledgetransferrequirements

Section Subject Work required

Propagation management

Stock plant and cutting nutrition

Research on the nutrient requirements of stock plants and cuttings, particularlywiththemoredifficulttorootsubjects

Cold storage of leafy cuttings Research to determine optimum storage times and temperatures todevelopspecificguidelinesforHNSsubjects

Lean management and its application to propagation work

Knowledgetransfertailoredtotheneedsofpropagatorstobuildconfidenceandraiseawarenessofthebenefitsofthistechnique

Wounding of cuttings Researchtoidentifyoptimumwoundingtechniquesfordifficult-to-rootsubjects(linkedwithnewworkonrootinghormones)

Leaf removal from cuttings Newresearchwithawiderrangeofsubjectstosubstantiateandbuild onpreviousworkasabasisforcroprecommendations

Rooting hormones Research to identify optimum formulations, combinations and rates for arangeofHNSsubjects

Propagation techniques

Improving propagation of difficulttorootsubjectsfromcuttings

Researchtodefineoptimumstockplantmanagement,propagationtiming, types of cuttings, treatments and rooting environments

Physiology of rooting

Newresearchtobetterunderstandwhysomecuttingsrooteasierthanotherstohelpimprovestrikerateswithmoredifficultsubjectsandenabletherootingofeasiersubjectstobebetterscheduledinlinewithmarketrequirements

Preconditioning cutting material

Linkedtostockplantmanagement,newworkondarkpreconditioningandlightingwithawider,morecontemporaryrangeofsubjectstodevelop practical, best practice guidelines for improved rooting using these techniques

Transport, storage and handling of cuttings

Researchanddevelopmentworktodetermineoptimumtransportandhandlingperiodsforrootedandunrootedcuttings,aroundwhichbestpractice guidelines can be established

Health status of cuttingsContinued development of on-site diagnostic kits for rapid and reliable disease screening of cutting material, such as Heuchera rust, bacterial and viral infections

Propagation environments and systems

Water management under mist systems

Research to compare rooting results on capillary beds under mist, using arangeofsystems,rootingmediaandplugtrays.Findpracticalwaysforgrowerstomeasuretheairtowatercontentofmedia across a range of plug and media types

The role of the EvaposensorSystematiccomparisonsofdifferentmistregimestoidentifytheoptimalset points for particular species and cultivars to enable nurseries to get the best from the Evaposensor mist control equipment

Aftercare

Crop protection Researchtoevaluatebenefitsandroleofmicrobialproductsin HNSpropagation

Integrated crop management Knowledgetransfertobuildconfidenceandpromotebestpractice,propagation and maintenance of disease-free material

Liverwortandmosscontrol Researchonpotentialproductsforcontrolwouldbeusefulalongwithcultural control and non-chemical control strategies

Cold storage of rooted plugs and liners

ResearchonHNSrequirementsprovidingfirmerrecommendations forgrowers

Researchandknowledgetransferrequirements133

AppendicesAp

pend

ix I

– D

ealin

g w

ith c

omm

on p

robl

ems

Man

agem

ent a

nd m

ater

ials

Wha

t?W

here

?W

hy?

Wha

t to

do

Insufficiento

rpo

or q

ualit

y pr

opag

atio

n m

ater

ial

Gen

eral

pro

blem

but

us

ually

mos

t com

mon

du

ring

the

busy

spr

ing

and

sum

mer

per

iods

Inad

equa

te s

tock

pla

nt m

anag

emen

t, includ

ingpo

orclones,insufficientp

lants,

lack

of p

rope

r and

tim

ely

prun

ing,

poo

r hu

sban

dry

Oldstockplantsno

long

ersuffi

ciently

prod

uctiv

e

Shor

tage

of s

uita

ble

nurs

ery

crop

s fro

m

whichto

propa

gate

Supp

lier i

ssue

s if

buyi

ng in

cut

ting

mat

eria

l

No‘quickfix’otherth

anbuyinginm

aterialorlinersordelaypropa

gation

until

sui

tabl

e m

ater

ial b

ecom

es a

vaila

ble

from

sto

ck

Lookahead

,forwardplanfu

turestockplantre

quirementsto

ensure

sufficienth

igh-qu

alitym

aterialisavailablewhenrequ

ired

Useclonaltruetotype

stockofh

ighhealthstatuswhenestablishing

st

ock

beds

Ensu

re g

ood

husb

andr

y to

mai

ntai

n pr

oduc

tivity

Prun

e st

ock

plan

ts re

gula

rly a

nd a

ppro

pria

tely

to m

axim

ise

high

-qua

lity

cutti

ng m

ater

ial a

nd ro

otin

g

Repl

ace

plan

ts o

n a

regu

lar a

nd p

hase

d

cycl

e to

ens

ure

cont

inui

ty o

f sup

ply

Onl

y bu

y in

cut

ting

mat

eria

l fro

m re

puta

ble

supp

liers

and

don

’t ju

st re

ly o

n on

e su

pplie

r

Whe

re s

oft c

uttin

gs a

re in

sho

rt su

pply,

root

an

early

bat

ch a

nd ta

ke

‘cuttingsfrom

cuttings’;itusuallyworkswellforquickro

otingsoftmaterial

Slow

throug

hputs

durin

g cu

tting

co

llect

ion,

pr

epar

atio

n an

d in

serti

on

Com

mon

plac

e du

ring

busyperiodsand

with

difficult-to-prepa

re

cutti

ng m

ater

ial,

for

exam

ple,

larg

e-le

aved

or

thor

ny s

tem

ed s

ubje

cts

Inad

equateorinefficientu

seofresou

rces

Poorstaffsupe

rvision

Poor

pre

para

tion

tech

niqu

e

Unn

eces

sary

leaf

rem

oval

from

cut

tings

Review

staffresources,procedu

res,workplacelayoutsandtra

iningneed

s

Useare

liablestaff

mem

berto‘service’thework,ensuringteam

mem

bers

don’trunsho

rtofm

aterialsand

soareab

leto

workcontinuo

usly

Review

cuttinghand

lingproced

ures

Noneed

tostripleavesfrom

manysubjects,suchasB

erbe

ris (e

verg

reen

), H

ebe,

Hea

ther

s, P

yrac

anth

a an

d Vi

burn

um ti

nus

Mon

itor o

utpu

ts th

roug

hout

the

day

Insufficientp

lug

plan

ts o

r lin

ers

fo

r sal

e or

grow

ingon

Canhap

penwith

anyt

hing

but

par

ticul

arly

withsloword

ifficult-

to-ro

otsub

jectswhere

wastagem

aybehigh

du

e to

pro

paga

tion

lossesorw

heresuitable

prop

agat

ion

mat

eria

l is

limited,especiallywhere

timin

g is

cru

cial

for

optim

um ro

otin

g

Bad

plan

ning

and

ove

r opt

imis

tic fo

reca

sts

for p

artic

ular

cro

ps

Notbuildinginsuffi

cientc

ontingenciesfor

slow

er,m

oredifficult,higherriskcrop

s

Inad

equa

te o

r uns

uita

ble

prop

agat

ion

mat

eria

l

Poor

pro

paga

tion

and

liner

per

form

ance

le

adin

g to

loss

es

Bere

alisticwhenplanning

,allowsuffi

cienttimeforc

ropsto

rootwell,grow

on

and

form

well-b

ranchedliners

Build

in c

ontin

genc

y m

easu

res

(suc

h as

ext

ra c

uttin

gs),

espe

cial

ly fo

r mor

e difficultsubjects

Prac

tice

good

sto

ck p

lant

man

agem

ent t

o en

sure

read

y an

d tim

ely

supp

lies

of a

dequ

ate

prop

agat

ion

mat

eria

l

Review

and

amendschedu

lesba

sedon

previou

sexpe

rienceandrecords

134 Appendices

Seed

pro

paga

tion

Wha

t?W

here

?W

hy?

Wha

t to

do

Poor

see

d ge

rmin

atio

nG

ener

al p

robl

emSe

ed d

orm

ancy

Poor

see

d qu

ality

and

sto

rage

Seed

sow

natwrong

timeforspe

cies

Seed

sow

ntoode

eply

Incorre

ctgerminationtempe

rature;u

sually,

theprob

lemisofte

nlowte

mpe

raturesbu

t,sometimes,too

highatempe

raturewill

inhi

bit g

erm

inat

ion

Germinationmaybenaturallyslow

(fore

xampleaswithdelayed

hypog

eal

germ

inat

ion

of P

aeon

ia)

Soilorgrowingmed

iahasdriedou

t

Wat

erlo

ggin

g

Mic

e da

mag

e

Checkseeddo

rmancy,q

ualityandsowingtim

eisapp

ropriatefo

rspe

cies

Sow

Aes

culu

s, C

asta

nea,

Fra

xinus

and

Que

rcus

in th

e au

tum

n ra

ther

than

springaswellasherbaceoussub

jectssuchas

Alch

emilla

, Eup

horb

ia,

Gen

tiana

, Lib

ertia

and

Prim

ula

Processandstoreseed

quicklyoncecollected

,whilefreshandingoo

dcond

ition

.Usehessiansackswhencollectingseed

ratherth

anpolythene

bags,keepseed

coo

land

transferto

coldstorage(3°C

)promptly

Usecoldstoragetobreakdormancyand

maintainseed

viabilitybe

tween

collectionandsowing

Checkand

amendsowingde

pths(usually,tw

icethede

pthofth

eseed

willsuffice)

Ensu

re b

ase

heat

is a

dequ

ate

and

deliv

erin

g re

quis

ite te

mpe

ratu

res

for

germ

inationwithindo

orsow

ings

Ensureseedbe

dsand

propa

gationmed

iaarewelldrained

and

not

overwatered

Che

ck to

ens

ure

mic

e or

sim

ilar p

ests

are

not

dam

agin

g se

eds

Seed

lings

co

llaps

ing

and

failin

g to

est

ablis

h

Gen

eral

pro

blem

Con

ditionsto

owetortoo

dry

Pest

dam

age

Damping

-offdiseaseorsimilar

Botry

tis in

fect

ion

Che

ck m

oist

ure

stat

us a

nd d

rain

age

of p

ropa

gatio

n m

ediu

m a

nd a

men

d as

nec

essa

ry

Che

ck fo

r sig

ns o

f pes

ts o

r dis

ease

s on

root

s an

d st

em b

ases

, rem

ovin

g aff

ectedplantsortraysand

using

suitablecontrolm

easures

Poor

see

dlin

g grow

thand

co

lour

(pal

ing

or

purp

ling)

Gen

eral

pro

blem

Acoolgrowingenvironm

entw

ithindo

or

sowings

Poor

nut

rient

upt

ake

Pest

or d

isea

se p

robl

em

Checkand

amendgrow

ingtempe

raturesasnecessary;chillin

gwillredu

ce

root

act

ivity

and

, in

turn

, nut

rient

upt

ake,

not

ably

of p

hosp

hate

and

iron

, de

ficienciesofwhichcanlead

toleafchlorosis,p

alingandpu

rpling

Alowte

mpe

raturecanalsocauseleafpurpling

Checkfo

rsignsofd

amping

-offorblackro

otro

tdisease

Appendices 135

Cut

ting

prop

agat

ion

and

root

ing

envi

ronm

ents

Wha

t?W

here

?W

hy?

Wha

t to

do

Poororslow

root

ing

of c

uttin

gsG

ener

al b

ut u

sual

ly m

ost

pron

ounced

withslowor

difficult-to-ro

otsub

jects

Somesubjectsarenaturallyslowro

oting

Poor

qua

lity

mat

eria

l

Materialinfloralcon

ditionratherth

an

vege

tativ

e

Poor

or i

napp

ropr

iate

pre

para

tion

Inap

prop

riate

root

ing

envi

ronm

ent

Inco

rrect

tim

ing

or ty

pe o

f cut

ting

Too

muc

h or

not

eno

ugh

root

ing

horm

one

Inap

prop

riate

root

ing

med

ium

Onl

y us

e he

alth

y, un

iform

and

goo

d qu

ality

cut

tings

, tak

en fr

om s

tock

plantsorstro

nggrowingnu

rserycrop

s

Prep

arecutting

scarefully,u

sing

stro

ngsho

ots,wou

ndingandusing

horm

one‘quickdips’wherebeneficial(forsem

i-ripe,slowor

difficult-to-ro

otsub

jectsandhardwoo

dcutting

s)

Form

oredifficultsubjects,takecutting

satth

eop

timum

timeforroo

ting;

in th

e ca

se o

f Ace

r, Az

alea

, Cot

inus

and

Syr

inga

dur

ing

April

and

May

as

softw

oodcutting

sun

derh

ighhu

miditym

isto

rfog

Usealigh

tslicewou

ndwithfirm

er,h

arde

rwoo

dand‘quickdip’h

ormon

es

ratherth

anta

lcprepa

rationswithD

aphn

e an

d Rh

odod

endr

on s

peci

es a

nd

difficult-to-ro

otevergreensandconifers

Usesup

portive,h

ighhu

midityro

otingenvironm

entsfo

rsloword

ifficultto

root

spe

cies

Checkth

erootingmed

iumm

ix;u

sepeat,gritandba

rkwithcon

ifersand

Ta

xus

for b

est r

esul

ts

Con

side

r oth

er fo

rms

of p

ropa

gatio

n, s

uch

as s

eed,

root

cut

tings

, etc

Une

ven

root

ing

Gen

eral

Wea

k or

poo

rly g

rade

d pr

opag

atio

n m

ater

ial

Ensurem

aterialiswellgrade

ddu

ringcollectionandprep

aration

Exce

ss c

allu

s fo

rmat

ion

arou

nd

cutti

ng b

ases

Gen

eral

, can

be

common

inslow-ro

oting

ever

gree

ns a

nd c

onife

rs

A hi

gh ro

otin

g te

mpe

ratu

re

Excessiveaerationlinkedtowateringand,

in tu

rn, a

lkal

inity

bui

ld-u

p of

the

root

ing

med

ium(forexample,withC

amel

lia,

X C

upre

ssoc

ypar

is le

yland

ii an

d Ta

xus)

Excessivewou

ndingorhormon

eap

plication

Che

ck a

nd re

duce

root

ing

tem

pera

ture

s if

requ

ired,

ens

ure

the

prop

agationmed

iumiswellstru

ctured

butnotexcessivelyope

nandavoid

overzealou

sho

rmon

eap

plication(useafive-secon

d‘quickdip’forbest

resu

lts, g

ener

ally

)

Easy

root

ing

sum

mer

pro

paga

ted

mat

eria

l sel

dom

requ

ires

muc

h ba

se

heat,w

ound

ingoruseofh

ormon

erootingaids

Wat

erlo

gged

and

ro

tting

cut

tings

Gen

eral

but

usu

ally

mor

e co

mm

on a

mon

g au

tum

n andwinterp

ropa

gated

crop

s al

thou

gh th

is c

an

occu

r in

poor

ly c

ontro

lled

mis

t env

ironm

ents

Poorwaterm

anagem

ent

Wat

erlo

gged

root

ing

med

ium

Checkand

correctwateringregimesand

hum

iditycon

trolsinm

ista

ndfo

gsystem

s.Useasensorform

osta

ccuratecontrol

Ensu

re b

oth

the

prop

agat

ion

med

ium

and

pro

paga

tion

bed

are

welldrained

Usebarkorwoo

d-fibreinth

erootingmed

ium

Avoidhigh

relativehu

midityaroun

doverwinteredcutting

sun

derp

rotection

Usecap

illarysandbe

ds(orp

orou

sconcretefloo

rs)toform

propa

gation

beds

and

pro

vide

pos

itive

dra

inag

e

136 Appendices

Cut

ting

prop

agat

ion

and

root

ing

envi

ronm

ents

(con

tinue

d)

Wha

t?W

here

?W

hy?

Wha

t to

do

Wilt

ing

and

colla

pse

of

cutti

ngs

Gen

eral

but

mos

t common

withearly

season

softwoo

dleafy

cutti

ngs,

incl

udin

g Ac

er,

Azal

ea, C

otin

us a

nd

Syrin

ga

Com

mon

in s

prin

g an

d su

mm

er if

mat

eria

l is

collected

atthewrong

tim

e an

d no

t han

dled

or

sto

red

prom

ptly

Waterlossdueto

leafwarmingandrapid

evap

otra

nspi

ratio

n

Poor

han

dlin

g an

d st

orag

e of

cut

ting

materialinthefieldprio

rtoprep

aration

an

d in

serti

on

Col

lect

ing

mat

eria

l dur

ing

hot p

erio

ds

Harvestcuttingswhencond

ition

sarecool

and

fresh

, and

tran

sfer

to c

ool,

shad

ed c

ondi

tions

pro

mpt

ly

Usecoldstorage(3°C

)forsho

rt-term

holding

ofcuttingmaterialand

to

remove‘fieldheat’

Usesup

portivero

otingenvironm

entsfo

rsoftwoo

dleafycutting

s

Checkand

amendshad

elevels,especiallywithspringandsummer

prop

agat

ed c

rops

und

er p

olyt

hene

Ensu

re b

oth

plan

t mat

eria

l and

med

ia in

tray

s an

d po

ts d

on’t

dry

out

Root

con

stric

tion,

cu

rling

and

da

mag

e

Gen

eral

pro

blem

but

worsewhencutting

sare

root

ed in

sta

ndar

d tra

ys

andloose-filledplug

tra

ys a

nd a

re le

ft to

o lo

ng b

efor

e ha

ndlin

g

HNSsubjectsth

at

disl

ike

root

dis

turb

ance

(in

clud

ing

Arbu

tus,

G

arry

a an

d he

rbac

eous

pl

ant s

ubje

cts

such

as

Alst

roem

eria

and

Di

eram

a)suff

erm

ost

Likewise,ro

otingdo

wn

into

bed

s by

vig

orou

s su

bjec

ts (s

uch

as

Acan

thus

, Bud

dlei

a,

Elae

agnu

s, E

upho

rbia

cy

paris

sias

and

Hyd

rang

ea) c

an b

e

a pr

oble

m, e

spec

ially

on

cap

illary

san

d be

ds

Dela

ys in

han

dlin

g an

d po

tting

on

root

ed

mat

eria

l

Worsewithstand

ardtra

ysorw

herecells

and

pots

are

too

smal

l for

the

size

of c

uttin

g or

vig

our o

f pla

nt

Vigo

rous

sub

ject

s ca

n be

a p

artic

ular

pr

oble

m, i

n te

rms

of ro

ot c

onst

rictio

n,

curli

ng a

nd ro

otin

g th

roug

h in

to b

eds

Cap

illarysandbe

dsth

atarekep

ttoo

wet

for t

oo lo

ng n

ear t

he s

urfa

ce e

xace

rbat

e ro

otin

g th

roug

h

Use

mod

ules

and

cho

ose

the

right

size

for t

he s

ubje

ct

Forsoftwoo

dcutting

s,usem

oduleswithpre-drilledho

lestoease

insertion

,orloo

se-fillplug

trays

Root

-trai

ners

and

bio

degr

adab

le tr

ays

and

pots

hel

p re

duce

root

co

nstri

ctio

n

Use

per

mea

ble

mem

bran

es o

ver s

and

beds

to re

duce

root

ing

thro

ugh

Don’tletsandbe

dssittoowet,especiallynearthesurfaceasthisdraws

rootsdo

wn

Pot o

n ro

oted

mat

eria

l pro

mpt

ly

Appendices 137

Cut

ting

prop

agat

ion

and

root

ing

envi

ronm

ents

(con

tinue

d)

Wha

t?W

here

?W

hy?

Wha

t to

do

Cut

tings

or l

iner

s dr

ying

out

and

sc

orch

ing

Softw

oodandsemi-ripe

leaf

y cu

tting

sH

igh

light

leve

ls, i

nade

quat

e sh

adin

g an

d rapidwaterloss

Wat

er s

corc

h fro

m o

verh

ead

irrig

atio

n ap

plie

d du

ring

hot,

brig

ht c

ondi

tions

Spra

y sc

orch

from

pes

ticid

e ap

plic

atio

n

Incr

ease

sha

ding

and

ven

tilat

e cr

ops

as c

ondi

tions

per

mit

Avoidoverhead

wateringdu

ringveryhot,b

rightperiodsunlesscrop

sare

wellshade

d

Onlyspraype

sticideswhennecessaryandneverd

uringho

t,brightspe

lls

whenleafscorchcaneasilyoccur;sprayinth

eearlym

orning

ore

vening

,usebiolog

icalpestc

ontro

loptionswherepossible

Cut

tings

pr

oduc

ing

shoo

ts

butfew

orn

oro

ots

form

ed

Gen

eral

but

qui

te

common

withhardw

ood

cutti

ngs

unle

ss ro

otin

g environm

entiswell

man

aged

and

can

be

aprob

lemwithfast-

grow

ingherbaceous

subj

ects

Mos

t usu

ally,

due

to to

o hi

gh a

n ai

r te

mpe

ratu

re c

ausi

ng b

uds

to b

reak

and

shoo

tsto

growahead

ofroo

tformation

Redu

ceairtempe

ratures(ventilate,shade

,usefans)tocontrolgrowth

Moveprotectedcrop

sou

tsideifsufficientlyestab

lished

Use

col

d st

orag

e to

hol

d ro

oted

and

unr

oote

d m

ater

ial f

or s

hort

perio

ds

tocon

trolgrowth

Mic

ropr

opag

atio

n

Wha

t?W

here

?W

hy?

Wha

t to

do

Mic

ropr

opag

ated

pl

antle

ts fa

iling

to

esta

blis

h

Mostc

ommon

withstage

3plantlets,w

hichre

quire

carefulw

eaning

Drying

outoro

verw

ettingarecommon

ca

uses

but

als

o ph

ysic

al d

amag

e du

ring

trans

it or

sub

sequ

ent h

andl

ing

A la

rge

amou

nt o

f mat

eria

l arri

ving

at

the

sam

e tim

e m

ay c

reat

e ha

ndlin

g an

d weaning

difficulties

Difficultsubjectsweanedinlessvisible

loca

tions

can

lead

to p

robl

ems

Dela

ys in

pric

king

out

sta

ge 3

mat

eria

l on

arrivaland

transferringsw

iftlyto

asuitably

supp

ortiv

e en

viro

nmen

t

Wea

ning

larg

e ba

tche

s of

pla

ntle

ts in

the

heat

of m

idsu

mm

er ra

ther

than

spr

ing

is

mor

e st

ress

ful t

o yo

ung

plan

ts a

nd c

an

lead

to lo

sses

Sche

dule

del

iver

ies

so th

ey d

on’t

all a

rrive

at o

nce

Handleyoungplantm

aterialquicklyonarrival,p

rickou

tswiftlyand

use

ahigh

hum

idityenvironm

enttoweanandestablishthem

(wetfo

g,closed

misto

rpolythenete

ntplusfleececovers)

Wea

n pl

ants

in a

hig

hly

visi

ble

plac

e so

they

can

be

seen

and

che

cked

at

leas

t dai

ly

Avoidweaning

inth

eheatofm

idsummerifpossible;th

eextra

heatstre

ss

canmakeweaning

especiallydifficult

Use

ple

nty

of s

umm

er s

hade

Buyindifficult-to-estab

lishsubjects(suchasH

euch

era)asweaned

plan

tlets

(sta

ge 4

) not

root

ing

cultu

res

(sta

ge 3

)

138 Appendices

Gra

fting

and

bud

ding

Wha

t?W

here

?W

hy?

Wha

t to

do

Poor

gra

ft ta

keNotspe

cificto

any

parti

cula

r sub

ject

Poor

qua

lity

stoc

ks (a

thin

ste

m d

iam

eter

) or

scionwoo

d

Poor

root

stoc

k ha

ndlin

g an

d st

orag

e (in

clud

ing

frost

dam

age

or d

esic

catio

n)

Stoc

k an

d sc

ion

may

not

be

com

patib

le

Graftunionflood

s(benchgrafting

)

Gra

ft un

ion

drie

s ou

t

Tim

ing

(som

e su

bjec

ts re

spon

d be

tter

duringspecificpe

riods)

Poorknife-w

orkandfailureto

makego

od

cam

bial

con

tact

Poor

or l

ack

of tr

aini

ng in

gra

fting

Usestro

ngstocks(usuallytw

oyearsoldfora

dequ

atestem

thicknessfor

grafting,especiallyfo

rfieldgrafting)

Useonlystrong

,well-ripened

,one-yearw

oodforscion

s

Che

ck s

tock

and

sci

on a

re c

ompa

tible

Bringstocksinside

atleastsixweeksahead

ofb

enchgrafting

todryback

andprom

otestrong

rootgrowth

Wax

con

ifer g

rafts

to p

reve

nt d

ryin

g ou

t

Checktiming:hardw

oods(w

inter),con

ifers(m

ainlyFebruaryand

March

but g

raft

ceda

rs in

sum

mer

), Ac

ers

and

Ham

amel

is (s

umm

er)

Usegentlebaseheatfo

rwinterb

enchgrafting

ofh

ardw

oodsorh

ot-pipe

callu

sing

Don’

t tie

-in to

o tig

htly

Keep

a‘sap

-drawer’(activeshoo

t)wherere

quiredandredu

cegradu

ally

once

the

unio

n ha

s fo

rmed

Bark/rind

difficult

to li

ftRo

ses

(‘T’ b

uddi

ng)

Dryfieldcon

ditionsprio

rtobu

dding

Tempe

raturestoolowfo

rade

quatesapflow

Aimto

bud

followingsteadyra

inorirrigation

Dela

y bu

ddin

g

Poor

bud

take

Notspe

cificto

any

parti

cula

r sub

ject

Poorqualitystocksorb

udwoo

d

Budwoo

dhasdriedou

t

Tim

ing

(too

early

or l

ate

depe

ndin

g on

se

ason

and

sub

ject

)

Bud

ties

too

tight

Poorknife-w

orkandcambialcon

tact(chip

budd

ing)

Poor

or l

ack

of tr

aini

ng in

bud

ding

ski

lls

Don’tu

sesofttipsorwellripened

stembaseswhenprep

aringbu

ds

Keep

bud

woo

dcool,m

oistand

awayfrom

directsun

(useacoldstoreif

mor

e th

an 2

4 ho

urs)

Chi

p bu

d M

alus

ear

ly a

nd P

runu

slater,T-bu

drosesfro

mearlyJuly

Useasharpknife,w

orkqu

ickly,neatlyand

accurately

Appendices 139

Afte

rcar

e

Wha

t?W

here

?W

hy?

Wha

t to

do

Recu

rring

prob

lemswith

pest

s an

d di

seas

es

Gen

eral

but

mos

t co

mm

on in

spr

ing

and

sum

mer

pro

paga

tion

crop

s, a

lthou

gh

damping

-off,sciaridfly

andvineweevillarvae

can

dam

age

autu

mn

and

winterc

rops,especially

youn

g se

edlin

gs a

nd

newlyro

oted

cuttings

Inad

equa

te c

rop

prot

ectio

n m

easu

res,

poo

r hy

gien

e an

d co

ntam

inat

ed p

ropa

gatio

n m

ater

ial,

plug

s an

d lin

ers

Ensu

re g

ood

nurs

ery

hygi

ene

Che

ck b

ough

t-in

plug

s, s

tock

pla

nts

and

liner

s ca

refu

lly o

n ar

rival

for s

igns

of

pro

blem

s an

d tre

at b

efor

e tra

nsfe

r to

nurs

ery

Mon

itorp

ropa

gationandlinercropsre

gularly;checkseedand

cu

tting

s da

ily

Usestickytrap

stom

onitorfl

ying

pestslikewhiteflies,thripsandsciarid

flyadu

lts

Usebiologicalcon

trolagentswhereavailableforsafeandeff

ectivecontrol

of p

ests

Wee

ds (i

nclu

ding

m

oss

and

liverwort)

frequ

ently

oc

curri

ng in

pr

opag

atio

n

area

s an

d lin

ers

Generalproblem

where

nurs

ery

hygi

ene

and

waterm

anagem

entis

poor.O

ftenworstamon

gslow

-rootingsubjects,

espe

cial

ly in

the

autu

mn

andwinterp

eriod

Poor

nur

sery

hyg

iene

Wee

d in

fest

ed p

lugs

Con

taminated

water,m

ediaortoo

ls,etc.

Overlywetpropa

gationenvironm

entsor

poorwaterm

anagem

ent

Review

nurseryhygienem

easuresandcorre

ctwherenecessaryto

redu

ce

backgrou

ndweedpressure

Coverwaterta

nksandgrow

ingmed

iastorageareas

Cle

an, d

isin

fect

or c

hang

e to

ols

regu

larly

Keep

waterm

anagem

entu

nderclosecon

troltoavoidoverlywet

cond

ition

sthatfavourweeds

Usem

ulchesorp

ermeabletra

ymatstocon

trolw

eedsinplugtra

ysand

po

t lin

ers

Use

per

mea

ble

mem

bran

es o

ver s

and

beds

to h

elp

keep

them

cle

an

Root

ed c

uttin

gs

appe

ar p

ale

and

failin

gtogrow

awaywell

Com

mon

problem

where

mat

eria

l is

held

for

leng

thy

perio

ds b

efor

e lin

er p

ottin

g, p

artic

ular

ly

amon

g qu

ick-

root

ing

and

vigo

rous

sub

ject

s pr

opag

ated

dur

ing

the

sprin

g an

d su

mm

er

Cuttingsm

ayhavelowcarbo

hydrate

rese

rves

due

to p

oor n

utrie

nt s

tatu

s of

sto

ck

plantsorn

urserycropsfrom

whichth

ey

weretakenornutrientleaching

mayhave

occu

rred

durin

g pr

opag

atio

n

Nutrientlevelsinro

otingmed

iumarelowor

have

exp

ired

Liqu

id fe

ed (5

0 pp

m n

itrog

en +

25

ppm

pho

spho

rus

+ 50

ppm

pot

assi

um)

rooted

cuttingsto

boo

stnutrientre

servesand

restorecolour;u

sefo

liar

feed

sifthemed

iumissuffi

cientlywetand

thispreclud

esliqu

idfeed

ing

Use

con

trolle

d re

leas

e fe

rtilis

ers

in th

e pr

opag

atio

n m

ediu

m to

sus

tain

grow

thand

qualityofro

oted

material

140 Appendices

Afte

rcar

e (c

ontin

ued)

Wha

t?W

here

?W

hy?

Wha

t to

do

Excessivegrow

th

of ro

oted

mat

eria

l or

line

rs

Com

mon

withfast-

grow

ingsummer

prop

agated

cropsgrown

on u

nder

pro

tect

ion

Vigo

rousvarietiescanbe

difficulttocon

tain

but h

igh

tem

pera

ture

s an

d hi

gh n

itrog

en

feed

pro

gram

mes

enc

oura

ge s

oft,

rapi

d grow

th,especiallyund

erprotection

Poor

pla

nnin

g an

d cr

op s

ched

ulin

g of

ten

createaneedforg

rowthcon

troland

can

resultinhighcrop

wasteifsup

plyisnotwell

mat

ched

to d

eman

d

Redu

cegrowingtempe

raturesandtra

nsfere

stab

lishedcrop

sou

tsidein

sum

mer

Sche

dule

pro

duct

ion

bette

r to

save

trim

min

g or

pru

ning

Ease

bac

k fe

edin

g an

d irr

igat

ion

regi

mes

Con

side

rusing

low-ratechem

icalgrowthre

gulatorsonestablishedliners

alon

gsid

e cu

ltura

l mea

sure

s

Poorwinter

surv

ival

of r

oote

d cu

tting

s

Generalproblem

where

root

ed c

uttin

gs o

r lin

ers

have

not

dev

elop

ed

sufficientlystro

ngro

ots

priortowinter

Directtissuedam

agebysub

-zerowinter

tem

pera

ture

s

Wat

erlo

ggin

g of

tray

s, p

ots

or b

eds

Poor

env

ironm

enta

l con

trol (

high

rela

tive

hum

idity

aro

und

cutti

ngs)

Poor

nur

sery

hyg

iene

lead

ing

to p

est a

nd

dise

ase

carry

-ove

r

Poor

root

ing

of c

uttin

gs, l

ate

prop

agat

ion

or

potti

ng o

f lin

ers

Use

of i

nfer

ior,

poor

qua

lity

cutti

ng m

ater

ial

Providead

equatewinterp

rotection(includ

ingheat,fleececoversetc.)and

ensurecuttingsand

sam

eseason

pottedlinersarewellestab

lishedprior

towinter

Ensurebed

s,potsandtra

ysarewelldrained

Practicego

odenvironm

entalcon

troltopreventm

aterialoverwinteringin

high

hum

idities,w

hichencou

ragesdiseasesand

decay

Use

onl

y st

rong

, goo

d qu

ality

pro

paga

tion

mat

eria

l and

pro

paga

te o

r pot

ea

rly to

ena

ble

cutti

ngs

or li

ners

to fo

rm g

ood

root

s ah

ead

ofwinter

Appendices 141

Appe

ndix

II –

A s

umm

ary

of p

ropa

gatio

n m

etho

ds fo

r a ra

nge

of w

oody

HN

S su

bjec

ts

HN

S su

bjec

tsSe

edSo

ftwoo

d cu

tting

sSe

mi-r

ipe

cutti

ngs

Har

dwoo

d cu

tting

sLe

af-b

ud

cutti

ngs

Root

cu

tting

sD

ivis

ion

Fiel

d gr

aftin

gBe

nch

graf

ting

Budd

ing

Laye

ring/

st

oolin

gM

icro

pro-

pa

gatio

nAb

elia

Abut

ilon

Acer

pal

mat

umAc

er n

egun

doW

& S

Actin

idia

Arbu

tus

BAu

cuba

Azal

ea (d

ecid

uous

)Az

alea

(eve

rgre

en)

Berb

eris

(dec

iduo

us)

Berb

eris

(eve

rgre

en)

WBe

tula

spe

cies

WBu

ddle

iaBu

xus

Cam

ellia

Car

pinu

sW

Car

yopt

eris

Cea

noth

usC

edru

sS

Cer

atos

tigm

aC

erci

diph

yllum

BL

Cer

cis

WC

haen

omel

esL

Cha

mae

cypa

ris

Chi

mon

anth

usL

Cho

isya

Cist

usC

lem

atis

Spec

ies

WC

lero

dend

ron

trich

otom

umC

onvo

lvulu

s cn

eoru

mC

ornu

s al

ba c

ultiv

ars

LC

ornu

s flo

rida

W &

SL

Cor

nus

kous

aW

& S

142 Appendices

Appe

ndix

II –

A s

umm

ary

of p

ropa

gatio

n m

etho

ds fo

r a ra

nge

of w

oody

HN

S su

bjec

ts

HN

S su

bjec

tsSe

edSo

ftwoo

d cu

tting

sSe

mi-r

ipe

cutti

ngs

Har

dwoo

d cu

tting

sLe

af-b

ud

cutti

ngs

Root

cu

tting

sD

ivis

ion

Fiel

d gr

aftin

gBe

nch

graf

ting

Budd

ing

Laye

ring/

st

oolin

gM

icro

pro-

pa

gatio

nAb

elia

Abut

ilon

Acer

pal

mat

umAc

er n

egun

doW

& S

Actin

idia

Arbu

tus

BAu

cuba

Azal

ea (d

ecid

uous

)Az

alea

(eve

rgre

en)

Berb

eris

(dec

iduo

us)

Berb

eris

(eve

rgre

en)

WBe

tula

spe

cies

WBu

ddle

iaBu

xus

Cam

ellia

Car

pinu

sW

Car

yopt

eris

Cea

noth

usC

edru

sS

Cer

atos

tigm

aC

erci

diph

yllum

BL

Cer

cis

WC

haen

omel

esL

Cha

mae

cypa

ris

Chi

mon

anth

usL

Cho

isya

Cist

usC

lem

atis

Spec

ies

WC

lero

dend

ron

trich

otom

umC

onvo

lvulu

s cn

eoru

mC

ornu

s al

ba c

ultiv

ars

LC

ornu

s flo

rida

W &

SL

Cor

nus

kous

aW

& S

HN

S su

bjec

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Appendices 143

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144 Appendices

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146 Appendices

Appendix III – References and further informationPropagation managementAHDB Horticulture factsheets• 09/05:Low temperature storage of bedding

plant plugs

• 05/05:Nutrition of container-grown hardy nursery stock

• 14/04:Hardy nursery stock – Management of stock plants

• 23/97:Pruning and preconditioning stockplants of ornamental shrubs

AHDB Horticulture grower guides• HNSCold Storage – Howto successfully cold

store hardy nursery stock

AHDB Horticulture project reports• HNS140:Survey to determine current industry

practice and future needs for the use of low temperature storage

• HNS136a:Management tools for optimising nursery space use and production forecasting

• HNS113:The feasibility of using low temperature storage as a scheduling aid in nursery stock production

• HNS41:Stock plant management and preconditioning

• HNS27:Propagation: Stock plant and cutting processes influencing subsequent plant quality

• HNS14:Clonal selection of hardy ornamental nursery stock cultivars

• PC 196a: Bedding plants: The use of low temperature storage as a scheduling aid in bedding plant production

Other sources of information• Delftvan,P.,2005.Preparingforanewpropagation

unit.IPPSCombinedProceedings55:243-247

• HRIEffordEHSHONSProgrammeReports1981 and 1982

• HRIEffordEHSHONSReviews1977,1978,1982,1983, 1984

• Lamb,J.G.D.,Kelly,J.C.,andBowbrick,P.,1985.NurseryStockManual,GrowerBooks

• Macdonald,B.,2000.PracticalWoodyPlantPropagationforNurseryGrowers,TimberPress

• O’Neill,K.,2005.Advantagesofin-housepropagation at Bransford Webbs Plant Company IPPS Combined Proceedings 55: 247-249

• Schonbeck,H.,1982.Isstrippingcuttingsnecessary? IPPS Combined Proceedings 32: 199-200

• Stanley,J.andToogood,A.,1980.TheModernNurseryman,FaberandFaber

Propagation techniquesAHDB Horticulture factsheets• 29/97:Containerising field budded trees

• 26/97:Field budding ornamental trees

AHDB Horticulture grower guides• Herbaceous perennials – A guide to the production

of container-grown plants

• HNSColdStorage–How to successfully cold store hardy nursery stock

• Practicalweedcontrolfornurserystock–An AHDB Horticulture growers’ handbook

AHDB Horticulture project reports• CP 74: Exploiting ethylene and wounding signalling

to promote adventitious root formation in hard-to-root ornamental species

• HNS155:Nursery stock: Herbicide screening for tree seed beds

• HNS45:Management opportunities in the budding nursery

• HNS40a:Optimising pruning of micropropagated and conventional propagated container-grown plants

• HNS32:Factors controlling the quality of micropropagated HNS liners

• HNS31a:Tree and shrub seed beds: Continued evaluation of weed control treatments

• HNS31:Evaluation of weed control treatments in tree and shrub seed beds and first outdoor transplants

• HNS29:Acer:Control of Verticillium wilt

• HNS20a:EMLA ornamental Prunus and Malus varieties and rootstocks: Field trials to promote their uptake

• HNS7and7a:An analysis of why bud grafting gives poor and inconsistent results for many ornamental trees

Other sources of information• Coombes,A.andHillierJ.,(Ed),2002.HilliersManual

of Trees and Shrubs (8th Edition), David and Charles

• Dunn,N.A.,1995.Theuseofhot-pipecallusingforbenchgrafting.IPPSCombinedProceedings45:139-141

• Edmonds,J.,1980.ContainerPlantManual,GrowerBooks

• Garner,R.J.,2003.TheGrafters’Handbook,Casell• Lamb,J.G.D.,Kelly,J.C.,andBowbrick,P.,1985

NurseryStockManual,GrowerBooks


• McMillan-Browse,P.D.A.,1979.Hardywoodyplantsfromseed,GrowerBooks

• Sheat,G.W.,1948.Propagationoftrees,shrubsandconifers, Macmillan

Appendices 147

• Stanley,J.andToogood,A.,1980.TheModernNurseryman,FaberandFaber

• Wells,J.S.,1985.PlantPropagationPractices.AmericanNurseryman

Propagation environments and systemsAHDB Horticulture project reports• HNS159:Nursery stock propagation: Nursery

evaluation and demonstration of the Evaposensor towards its commercial availability as a mist controller

• HNS76:HNS:Examination of techniques to raise humidity in mist houses

• HNS9:Understanding the environmental needs of leafy cuttings during rooting

Other sources of information• ADASPamphletP3002,1986.Suntunnel

propagationofsoftwoodcuttings


• HRIEffordEHSHONSReviews1977,1978,1982,1983, 1984

• Humphrey,B.E.,1985.CommercialaspectsofdirectstickingofcuttingsatHilliers.IPPSCombinedProceedings 35: 464-468

• Kelly,A.,1986.DirectstickingofevergreenAzaleacuttings.IPPSCombinedProceedings36:333-335

• Lamb,J.G.D.,Kelly,J.C.,andBowbrick,P.,1985NurseryStockManual,GrowerBooks


• Scott,M.A.,1985.Progresswithdirectstickingofcuttings.IPPSCombinedProceedings35:458-463

• Stanley,J.andToogood,A.,1980TheModernNurseryman,FaberandFaber

AftercareAHDB Horticulture factsheets• 30/97:Maximising cutting survival during winter

• 05/01:Glasshouse whitefly and leafhoppers in protected herbs: Options for control within IPM programmes

• 01/02:Growth regulation of ornamental plants by reduced phosphorus availability

• 14/04:Hardy nursery stock – Management of stock plants

• 16/04:Control of Phytophthora, Pythium and Rhizoctonia in container-grown hardy ornamentals

• 05/05:Nutrition of container-grown hardy nursery stock

• 08/05:The biology and control of two-spotted spider mite in nursery stock

• 09/05:Low temperature storage of bedding plant plugs

• 13/06:Caterpillars of protected ornamental crops

• 10/07:Guidelines on nursery hygiene for outdoor and protected ornamental crops

• 06/08:A guide to best practice in handling bought-in plants

• 13/09:Guidelines for minimising latent grey mould in cut flowers and pot plants

• 25/12:Non-chemical weed control for container-grown hardy nursery stock

• 03/14:Use of chemical disinfectants in protected ornamental production

• 20/15:Control of whiteflies on protected ornamental crops

• 24/16:Vine weevil control in hardy nursery stock

• 18/17:Methods and equipment for matching irrigation supply to demand in container-grown crops

AHDB Horticulture grower guides• Hardy nursery stock Crop Walkers’ Guide

• Bedding and pot plants Crop Walkers’ Guide

• HNSColdStorage–How to successfully cold store hardy nursery stock

• Practical weed control for nursery stock – An AHDB Horticulturegrowers’handbook.

AHDB Horticulture project reports• HNS185:Understanding and managing crop

protection through integrated crop management

• HNS175:Liverwort control in HONS using novel techniques

• HNS155:Nursery stock: Herbicide screening for tree seed beds

• HNS126:Biology, epidemiology and control of liverwort infestation of nursery plant containers

• HNS125:Hardy Ornamentals: The potential of compost teas for improving crop health and growth

• HNS113:The feasibility of using low temperature storage as a scheduling aid in nursery stock production

• HNS105and105b:Hardy nursery stock: Integrated control of snails and slugs

• HNS97:Improving the control and efficiency of water use in container-grown hardy ornamental nursery stock

• HNS93c:Protected container-grown nursery stock: Chemical and non-chemical screening for moss and liverwort control in liners

• HNS93:Nursery stock propagation: Moss, liverwort and slime control

• HNS90:Nursery stock propagation: Nutrition of rooted cuttings in modular trays

• HNS84:Development of effective overwintering strategies for rooted cuttings and young liners

148 Appendices

• HNS69:Ornamental shrubs: Developing the concept of the designer liner

• HNS55:Strategies for liner production designed to achieve high-quality container plants

• HNS49b:Influence of environmental factors and crop management on the incidence of disease on liners of overwintered hardy nursery stock species

• HNS44:Pre and post-rooting storage of softwood and hardwood cuttings

• HNS42and42a:Supplementary lighting for alpines, herbaceous perennials and hardy nursery stock species

• HNS39and39a:Container-grown nursery stock: Growth regulation

• HNS35g:Chemical weed control in container-grown nursery stock under protection

• HNS35b:Container HNS: Herbicide screening under protection

• HNS31a:Tree and shrub seed beds: Continued evaluation of weed control treatments

• HNS31:Evaluation of weed control treatments in tree and shrub seed beds and first outdoor transplants

• HNS27:Propagation: Stock plant and cutting processes influencing subsequent plant quality

• PC 239 and PC 239a: Protected herbs, ornamentals and celery: Development of an on-nursery rearing system for Atheta coriara for reduced cost biological control of sciarid and shore flies

Other sources of information• Barba,R.C.andPokorny,F.A.,1975.Influenceofthe

photoperiodonthepropagationoftwoRhododendroncultivars.J.HortSci.,50:55-9


• HRIEffordHONSReviews1977,1978,1982, 1983, 1984

• Kelley,J.D.,1965.Rootingofcuttingsasinfluencedbythephotoperiodofthestockplant.Proc.Int.Pl.Propag.Soc.,15:186-9

• Kramer,P.J.,1937.Photoperiodicstimulationofgrowthbyartificiallightasacauseofwinterkilling.PlantPhysiol.12:881-883

• Lamphear,F.O.andMeahl,R.P.,1963.Influenceofendogenous rooting co-factors and environment on seasonalfluctuationinrootinitiationofselectedevergreencuttings.Proc.Am.Soc.Hort.Sci.,83:811-18

• Loach,K.andWhalley,D.N.,1975.Useoflight,carbondioxideenrichmentandgrowthregulatorsintheoverwinteringofhardyornamentalnurserystockcuttings.ActaHorticulturae,54:105-116

• Loughall Research Station Annual Report, 1979

• Vince-Prue,D.,1975.Photoperiodisminplants.McGrawHill,London

• Waxman,S.,1955.Theeffectofthelengthofdayonthegrowthofwoodyplants.Proc.Int.Pl.Propag.Soc.,5:47-50

• Waxman,S.,1957.Thedevelopmentofwoodyplantsasaffectedbyphotoperiodictreatments.PhDThesis,CornellUniversity,Ithaca,NewYork.CitedinADASQRev.(1977)25:41-62.Theeffectsofphotoperiodonrootingandgrowthofhardyornamentals,D.N.Whalley,GCRI

• Waxman,S.,1965.Photoperiodictreatmentanditsinfluenceonrootingandsurvivalofcuttings‘Lightingundermist’.Proc.Int.Pl.Propag.Soc.,15:94-7

• Whalley,D.N.andCockshull,K.E.,1972.Someeffectsofphotoperiodontherootingofcuttings.NurseryandGardenCentre.,155:138-9

• Whalley,D.N.andCockshull,K.E.,1976.Thephotoperiodiccontrolofrooting,growthanddormancy in Cornus albaL.ScientiaHort.,5:127-38

• Willoughby,I.,Clay,D.andDixon,F.,2003.Theeffectof pre-emergent herbicides on germination and early growthofbroadleavedspeciesusedfordirectseeding.Forestry76:83-94

• Willoughby,I.,Dixon,F.L.,Clay,D.andJinks,R.L.,2007.Toleranceofbroadleavedtreeandshrubseedlingstopre-emergenceherbicides.Forestry34:1-12

International Plant Propagators’ Society case studiesOther sources of information• Fairweather,P.,2000.IPPSYearbook.

A fragrant obsession

• Upson,T.andAndrews,S.,2008.TheGenusLavandula. IPPS Grafting Workshop

Appendices 149

Appendix IV – Glossary of terms

Air-filledporosity(AFP) – a measure of the air space withinagrowingmedium.Apical cutting–acuttingwithanintactshoottip.Bud wood–shootsfromwhichbudsforbuddingareprepared.Carbohydrate – organic compounds comprising carbon,hydrogenandoxygen,whichareimportantinmetabolismandenergystorage.Inplants,sugarsand starches are responsible for energy storage andcelluloseisthestructuralbuildingblock;thesecompoundsareformedduringphotosynthesis.Clone – the vegetatively produced progeny of a singleplant.Controlled release fertiliser (CRF) – fertiliser productsfromwhichnutrientreleaseisdeterminedbytemperature and moisture levels to provide a release of nutrientstomatchplantgrowth.Day neutral plants –plantsforwhichdaylengthhas noeffectonflowering.‘Dry fog’ –referstofoginwhichalargeproportionofthefinewaterdropletsaresmallenoughtoremainsuspendedintheairforarelativelylongtime.Itcan,therefore, maintain a high level of humidity in the propagationenvironmentwithrelativelylittlewettingofthegrowingmedium,cuttingsandothersurfaces.Dry weight–ameasureofphotosyntheticgrowthwidelyusedwhenassessingtrialswork.Fog – a term used to describe a mass of droplets of condensedwatervapoursuspendedintheairandusedforhighhumiditypropagation.Itdiffersfrommistinthatthewaterdropletsfromfogremaininsuspensionforalongerperiodthanmist.Grafting – the preparing and joining of plant parts (scion androotstock)sothattheymaygrowtogether.Lignification–thenaturalplantprocessbywhichsoftstemsripenandbecomehardandwoody.Liner –ayoung,well-rootedplantpropagatedineither a large cell, small pot or the open ground and suitable forgrowingontosaleablesize,eitherinpotsortheopenground.Typically,potlinersareproducedin7,8 or9cmsizecontainers.Initsbroadestsense,thetermliner can mean anything from a seedling in a module to atreewhip.Long day plants–plantsforwhichnight-breaklightingordaylengthextensionstimulatesflowering.Mist–atermusedtodescribeamassofwaterdropletsintheairthatarenotgenerallysuspendedlikethefinerwaterdropletsfoundinfog.Photoperiod–therelativelengthofdayandnight.Photosynthesis–theprocessbywhichplantsuselighttoconvertcarbondioxideandwaterintocarbohydrates,so providing the energy and building blocks that plants requiretosurvive,propagateandgrow.

Potential evapotranspiration (ETp)–arateatwhich acropwouldlosewaterunderprevailingenvironmentalconditionsifthewatersupplywasnon-limiting.Itincludes evaporation from the plant (transpiration) and fromthesoilorgrowingmediuminthepot.Thiscanbeexpressedasaquantityofwaterlostovertime,byweight,volumeormmofwaterper24hours.Pre‑branched cutting – a cutting that has formed secondarylateralswhilestillattachedtotheplant.Relative humidity (RH) –ameasureofthewater vapour present in the air, expressed as a percentage ofthatwhichwouldbepresentiftheairwassaturatedandatthesametemperature.Respiration–theprocessbywhichenergyisreleasedfromcarbohydratesintheplant,duringwhichoxygen istakenupandcarbondioxidegivenoff.Rootstock–therootbearingplantonwhichascion orbudisgraftedorbudded.Scion – the part of a plant used for grafting onto arootstock.Scion wood–shootsfromwhichscionsarecut.Short day plants–plantsforwhichnight-break lightingordaylengthextensioninhibitflowering.Stomata – small pore-like openings, mainly on the undersideoftheleaf,whichareabletoopenand close, so providing a means of regulating carbon dioxide,oxygenandwatervapouruptakeand loss,asappropriate.Tipping –aformoflightpruning,wherebytheapical tipisremovedfromashootorcutting.Top‑working – the grafting of a scion onto a long uprightstemtocreateaparticularplanthabit.Transpiration–thelossofwaterbyevaporationviathestomatalopeningsontheleafsurface.Understock – a term sometimes used instead of rootstock.Vapourpressuredeficit(VPD) –ameasureofhow fartheairisfrombeingsaturatedwithwatervapour. It is measured in units of pressure because the vapour pressureofwaterinairisaconvenientmeasurement ofitsconcentration.‘Wet fog’–fogwitharelativelyhighproportionofwaterdropletsthatarelargeenoughtofalloutrapidly.Worked – a term commonly used to describe plants propagatedbybuddingorgrafting.

150 Appendices

Acknowledgements ThedevelopmentofthisguidewouldnothavebeenpossiblewithoutthecontributionsofmanyotherswithintheHNSindustry,towhomAHDBHorticultureisgrateful.Inparticular,thanksgotothefollowingpeoplefor their time and technical expertise throughout the preparationandwritingoftheHardyNurseryStockPropagation Guide:AlastairHazell,DarbyNurseryStockLtdBill Godfrey, W Godfrey and Sons LtdBrianHoward(Dr)Brian Humphrey, OBEChris Burgess, CB Consultant AgronomistChrisLane,WitchHazelNurseryDavidHide,WalbertonNurseryDavidMillais,MillaisNurseriesDavid Talbot, ADASDennis FordhamGeoffDeLaCour-Baker,PalmsteadNurseriesLtdJohnAtwood,ADASJohnBuxton(Dr),ADASJohnCooley,ProptekKarlO’Neill,TheBransfordWebbsPlantCompanyLeeWoodcock,PalmsteadNurseriesLtdMargaret Scott, MBEMarkHoward,JohnWoodsNurseriesLtdMikeNorris,NewPlaceNurseriesLtdNealWright,MicropropagationServicesLtdNeilAlcock,SeiontNurseriesNickDunn,FrankPMatthewsLtdNickReese,Jackdaws’FieldNurseryPaulHowling,HowardNurseriesLtdPaulMcKarry,P&SNurseryStockPeterBingham,KingfisherNurseryPetervanDelft,WestEndNurseriesPhillipMacMillanBrowseRichard Harrison Murray, RHM ScienceStephanieDunnJames,FrankPMathewsLtd

Appendices 151

Photographic and image creditsPage Image Source

Cover Griselinia plug plant NewPlaceNurseries–NeweyGroupPerennialPlugs and Liners

Propagation management7 Mechanical lift WestEndNurseries7 Mobile benching WestEndNurseries8 Fog/mistsysteminthepropagationunit PalmsteadNurseriesLtd8 Shade screens PalmsteadNurseriesLtd11 Container-grownstockplants PalmsteadNurseriesLtd12 Field-grownstockplants ADAS12 Stock plants on raised beds ADAS14 Shade provision over evergreen stock plants ADAS14 Stockplantsgrownunderprotection ADAS16 Alpine stock plants PalmsteadNurseriesLtd21 Stock plant material for cuttings ADAS22 Cuttings in a cool box ADAS22 Cutting insertion ADAS23 Cutting insertion team ADAS24 Cutting insertion into preformed plugs ADAS24 Snips and cutting material ADAS28 Singleslicewound DavidHide,WalbertonNursery28 Incisionwounding DavidHide,WalbertonNursery28 Splitwounding DavidHide,WalbertonNursery31 Root constriction Proptek35 Effectofcontrolledreleasefertiliserinthemedia ADAS35 Benefitsofcontrolledreleasefertiliserwithbark ADAS

Propagation techniques41 Seed store ADAS42 Seed beds Dennis Fordham42 Seedsowingindrills Dennis Fordham43 PowderymildewonAcer ADAS44 Seedsowingintrays Dennis Fordham45 Vermiculite cover over seed trays Dennis Fordham45 Deep rooting modules Dennis Fordham46 Stem section and cuttings DavidHide,WalbertonNursery47 Nodaltipcutting DavidHide,WalbertonNursery47 Internodal cutting DavidHide,WalbertonNursery47 Heel cutting DavidHide,WalbertonNursery48 Basal cutting DavidHide,WalbertonNursery48 Softwoodcutting DavidHide,WalbertonNursery49 Semi-ripe cutting DavidHide,WalbertonNursery49 Softwoodandsemi-ripecuttings NewPlaceNurseriesLtd50 Cuttings for fruit tree rootstock production NickDunn50 Hardwoodcuttingalongsidesecateurs DavidHide,WalbertonNursery51 Leaf-bud cutting DavidHide,WalbertonNursery51 Root cuttings in a tray ADAS52 Acanthus in a plug tray HowardNurseriesLtd53 Multiplication of stock during micropropagation WalbertonNursery54 Jarsofplantmaterial Micropropagation Services Ltd55 Plantletsunderfleece SeiontNurseries

152 Appendices

Page Image Source55 Micropropagated Heuchera SeiontNurseries56 Multiplication of stock during micropropagation Micropropagation Services Ltd57 Individual Heuchera plug SeiontNurseries58 Budding and grafting knives NickDunn59 Bud patch on rose David Austin Roses59 Polythene budding tape JohnRichardsNurseriesLtd60 Potted rootstocks JohnRichardsNurseriesLltd60 Field-grownstockplant NickDunn61 Rootstock and scion AHDB61 Scionwoodinstore NickDunn63 Grafted Quercus AHDB64 Whip/splicegraft NickDunn65 Side veneer graft NickDunn66 Modifiedsideveneergraft–rootstocktongue NickDunn66 Modifiedsideveneergraftbeingtiedup NickDunn66 Completedwhipandtonguegraft NickDunn67 Making the required cuts in the ‘T’ budding process David Austin Roses68 Bud selection David Austin Roses68 Close-up of bud and shield David Austin Roses68 Bud insertion into rootstock David Austin Roses68 Bud patch David Austin Roses68 Bud patch degradation David Austin Roses69 Final union David Austin Roses69 Rootstock cuts in the chip budding process NickDunn69 Bud in position in rootstock NickDunn

64-69 Grafting and budding illustrations StephanieDunnJamesandFrankP.MatthewsLtd.70 Chip bud tied in NickDunn70 Chipbudoncontainer-grownrootstock NickDunn71 Tray of bare-root grafts NickDunn71 Bare-root grafts being laid out NickDunn71 Graftsinpositionforhotwatercallusing NickDunn72 Heat placement on grafts NickDunn73 Irissplitsawaitingpotting HowardNurseriesLtd74 Stool beds NickDunn75 Close-up of stool bed NickDunn

Propagation environments and systems79 Shade over polythene tents ADAS83 Basal heat from heating cables ADAS83 Basalheatfrompipedhotwater ADAS83 Bed mist systems NewPlaceNurseriesLtd86 Evaposensor unit NewPlaceNurseriesLtd89 Polythene tent over cuttings ADAS89 Contact polythene over cuttings ADAS91 Sun tunnels MAFF,nowDefra94 Root development on cuttings in a heated bin NickDunn95 Direct struck Prunus PalmsteadNurseriesLtd

Aftercare96 Sciaridflylarvaeonstembase ADAS98 Neoseiulus cucumeris ADAS99 Sciaridflylarva ADAS99 Adultsciaridfly ADAS

Appendices 153

Page Image Source99 Adult Hypoaspis ADAS100 Atheta coriaria Syngenta Bioline Ltd100 Water snail ADAS101 Westernflowerthrips ADAS101 Two-spottedspidermites ADAS102 Vineweevillarvae ADAS102 Adultwhitefly ADAS103 Botrytis PalmsteadNurseriesLtd103 Weeds along bed edge ADAS104 Loose-fillmulch NewPlaceNurseriesLtd105 Tray mat Engro BV108 Seed bed Quercus AHDB110 Plugmediumwithcontrolledreleasefertiliser ADAS111 Trays of rooted cuttings ADAS111 Cuttingswithandwithoutliquidfeeding ADAS113 Crop trimming The Bransford Webb Plant Company115 Litgrowthchamber Micropropagation Services Ltd117 Frost damage Dove Associates118 Root development in a plug Proptek121 Capillary sand bed ADAS122 Pre-branched Photinia cuttings PalmsteadNurseriesLtd

International Plant Propagators’ Society case studies124 Grafted Hibiscus ADAS125 Lavender stock plant DavidHide,WalbertonNursery125 Internodalsoftwoodtipcuttingsoflavender DavidHide,WalbertonNursery126 Lavender cuttings under a polythene tent DavidHide,WalbertonNursery126 Rooted lavender cuttings in a plug tray DavidHide,WalbertonNursery127 Azalea and Rhododendron cuttings under a polythene tent David Millais128 Hebe plug The Bransford Webb Plant Company129 Finished Hebe plant The Bransford Webb Plant Company131 On-site testing Tim Pettitt132 Mossandliverwortcontrol AHDB132 Cold store AHDB

ThispublicationisintendedtoprovidegrowerswithinformationontheresultsandpracticalapplicationsfromAHDBHorticultureandnon-AHDBHorticulturefundedresearchanddevelopment.Itisnotintendedtoendorseorrecommendtheuseofanyproductsoractiveingredientsmentioned.Onlyproductsofficiallyapprovedasplantprotectionproductsshouldbeappliedtocontrolpest,diseaseandweedproblemsorusedasplantgrowthregulators.Beforeusinganysuchsubstances,growersshouldrefertotheproductapproval,labeloroff-labelinformation.

154 Appendices

155

Produced for you by:AHDB Horticulture Stoneleigh Park Kenilworth Warwickshire CV8 2TL

T 024 7669 2051 E [email protected] W horticulture.ahdb.org.uk

@AHDB_HortIf you no longer wish to receive this information, please email us on [email protected]

While the Agriculture and Horticulture Development Board seeks to ensure that the information contained within this document is accurate at the time of printing, no warranty is given in respect thereof and, to the maximum extent permitted by law, the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted from this document.

© Agriculture and Horticulture Development Board 2019. All rights reserved.

30003 0422

Produced for you by:AHDB Horticulture Stoneleigh Park Kenilworth Warwickshire CV8 2TL

T 024 7669 2051 E [email protected] W horticulture.ahdb.org.uk

@AHDB_HortIf you no longer wish to receive this information, please email us on [email protected] 30004 0422

While the Agriculture and Horticulture Development Board seeks to ensure that the information contained within this document is accurate at the time of printing, no warranty is given in respect thereof and, to the maximum extent permitted by law, the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted from this document.

© Agriculture and Horticulture Development Board 2019. All rights reserved.

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