Volume 2, Number 1, Page 1 Winter, 1998

Summer, 1997

In This Issue... 1 Container Soils 4 News From the Ex Files

6 Notes From the Chair5 New Sustainable Landscape 7 Profiles in EHThe University of California, in compliance with the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, sections 503 and 504 of the Rehabilitation Act of 1973, and the Age Discrimination Act of 1975, does not discriminate on the basis of age, religion, color, national origin, sex,

mental or physical handicap, or age in any of its programs or activities, or with respect to any of its employment policies, practices, or procedures. Nor does the University of California discriminate on the basis of ancestry, sexual orientation, marital status, citizenship, mental conditions (as defined in section12926 of the California Government Code), or because individuals are special disabled veterans or Vietnam era veterans (as defined by the Vietnam Era Veterans Readjustment Act of 1974 and Section 12940 of the California Government Code). Inquiries regarding this policy may be directed to the AffirmativeAction Director, University of California, Agricultural and Natural Resources, 300 Lakeside Drive, 6th Floor, Oakland, CA 94612-3560, (510) 987-0097).

GROWING Points Department of Environmental Horticulture • University of California, Davis

Anyone who has taken a horticulture course has learned the functions of soil as a growing medium. Soil providesmoisture, air, mineral nutrients, and anchorage for the plant. The latter function, anchorage, has posed a problem sinceancient times because of the itinerant nature of people: How could they keep a plant anchored, yet take it with themfrom place to place? It is likely that the desire to transport plants provided the impetus for cultivating plants incontainers.

The Development and Properties ofContainer Soils - Making a Good MixBy Richard Evans, Cooperative Extension Specialist

At a wholesale nursery, a mix of peat, perlite, sand and fiber bark is usedto pot Nandina domestica seedlings in one-gallon containers.

Records from ancient Egypt, for example,depict the transport of trees growing in largecontainers. By the fifth century BC, during theHellenistic period in Athens, the culture ofplants in containers was common, and somefast-growing herbaceous specieswere cultivated in pots for useduring festivals. In all likelihood,many of those ancient gardenersexperienced difficulty growingplants in containers filled withordinary garden soil. A containerprovides a relatively shallow res-ervoir of limited volume, with anair boundary delimiting its bot-tom. As a result, plants grown incontainers are subjected to moreintense environmental stressesthan those grown in a field. Thelong stream of frustrated garden-ers during the past four or fivethousand years has introduced in-cremental improvements in con-tainer soils through addition ofamendments such as animal ma-nure, leaf mold, sand, and woodashes. Nevertheless, because amendment of pot-ting soils was generally based on trial and errorrather than on good horticultural principles,results were inconsistent and recipes for pottingmixes became increasingly complicated.

The first concise description of the re-quired characteristics of a potting soil wasmade by John Lindley, an English professor ofbotany. He presented his ideas in The Theoryand Practice of Horticulture, a very interesting

book which was published in 1855. Lindley wasthe first to ascribe great importance to the physi-cal properties of what he called “artificial soil.”He recommended that horticulturists preparepotting soils from combinations of loam, sand,

and peat or other organic matter, depending onthe type of plant to be grown. Although this wasa major step toward systematic preparation ofpotting soils, horticulturists were still faced withthe complexity imposed by variable, poorly

defined ingredients and a largenumber of recipes for specificcrops.

The earliest prominent at-tempt to develop a standardizedpotting soil was made in 1939 byW.J.C. Lawrence and J. Newellof the John Innes HorticulturalInstitution in England. A “myste-rious wilt” in 1933 had killed asubstantial number of Chineseprimulas intended for their re-search, so they decided the nextyear to replace the potting soilwith a sterilized soil. To theirsurprise, seed germination in thesterilized soil was poor and sub-sequent plant growth was unsat-isfactory. They set about to deter-mine the cause of poor growth insterilized soil and to reduce what

they called “the old complexity” by standardiz-ing potting mixes. They elaborated on the crite-ria established by Lindley and, perhaps stillsmarting from the setback to their researchcaused by the loss of primulas, added as a

Volume 2, Number 1, Page 2 Winter, 1998

Table 3. Additives used to correct pH and increase fertility.

Mix Total Water- Air-filled Bulk Porosity holding Porosity Density

——— (% by volume) ——— (g cm-3)

Coir 95 79 16 0.08

Rockwool:Peat (1:2) 95 60 35 0.20

Dialoam 85 56 29 0.39

Dialoam:Peat:Redwood:Sawdust (1:1:1) 91 66 25 0.19

Expanded shale 66 43 23 0.89

are toxic to plants. Nurserymen also objected tothe lengthy composting requirement, which con-sumed time, space, and labor, and to the back-straining weight of the mix.

The next major advance was the develop-ment of University of California mixes in themid-1950s. The burgeoning nursery industry inCalifornia did not have access to sufficientamounts of the loam soils required for the JohnInnes mixes, nor did nurserymen want to con-tend with the demands for time and space toprepare compost. Baker, Matkin, and Chandlerof UCLA created several recipes for potting

mixes. The basic mix was 50% fine sand and50% peat or other organic matter. The emphasiswas on inexpensive, simple ingredients. UCmixes offered several advantages over previousrecipes: Toxicity was eliminated by using sandand peat instead of soil; the mix was easilyreproducible because the ingredients are uni-form; the mix could be prepared quickly be-cause no composting was required; and theweight was substantially less.

Many more recipes, variations on thesame theme, have been created since then. Thedevelopment of these recipes has been prompted

Table 1. Physical properties of components commonly used in potting soils.

Table 2. Physical properties of potting soil amendments.

Fertilizer or amendment Analysis lb/cubic yard

Potassium nitrate (KNO3) 13-0-46 1

Single superphosphate 0-20-0 2

Dolomite 5

Ferrous sulfate (FeSO4°7H

2O) 1

Mix Total Water-holding Air-filled Bulk Wet Porosity Capacity Porosity Density Weight

—— (% by volume) —— (g cm-3) (lb ft-3)

Sphagnum Peat 94 84 10 0.10 59

Peat-Perlite (1:1) 93 54 39 0.14 41

Peat-Vermiculite (1:1) 94 81 13 0.23 62

UC Mix(1 sand:1 Redwood sawdust:1 Peat) 73 57 16 0.67 71

criterion that the potting soil be free from harm-ful organisms and substances. Lawrence andNewell developed the John Innes compost, whichcontained three main components: loam soilfrom grassland, composted for six months withanimal manure and straw; coarse sand (moreproperly, grit) with a particle diameter of 1/16 to1/8 inch; and peat moss. This potting soil be-came widely used, but there were some prob-lems with it. Loam soils from grassland vary intheir physical and chemical properties, and theyare not available in all areas. Moreover, someloams release substances during steaming that

Volume 2, Number 1, Page 3 Winter, 1998

Summer, 1997

The height of the saturated zone in a container depends onthe particle size of the potting mix.

Gravel (gray balls) at the bottom of a container does notimprove drainage, but it does shift the saturated zone (darkband) up higher in the container.

The height of the saturated zone (dark band) in a containerdepends on the particle size of the potting mix. The depth ofthe mix in a container does not affect the height of thesaturated zone.

does, however, affect the extent to which thesurface of the mix is drained. Thus, a mixcontaining fine particles may be excellent fortall containers, but too wet for shallow contain-ers or flats.

Since roots require oxygen as well aswater, the presence of an extensive saturatedzone will inhibit growth and even cause death of

roots. It is commonly believed thatdrainage from a potting mix can beimproved by putting coarse mate-rial, such as gravel, at the bottom ofthe pot. In fact, this does not usuallyimprove drainage. Since the extentof the saturated layer depends onlyon the pore size of the mix, a layer ofcoarse material will not affect drain-age. Instead, it will decrease theeffective depth of the container.

The most important physicalproperties of a potting mix are air-filled porosity (the percentage of agiven volume of a potting mix thatis occupied by air after irrigationand drainage) and water holdingcapacity (the percentage of a givenvolume of a potting mix that isoccupied by water after irrigationand drainage). Good potting mixesgenerally have an air-filled porosityof at least 10%. This provides asufficient amount of air to meet therespiration needs of plant roots un-til additional air diffuses throughthe mix. The water-holding capac-ity should be at least 40%. This isusually enough water to sustain theplant for a day, so that constantrewatering isn’t necessary.

There are many materials thatcan be combined to establish theseproperties. The main factors to con-sider when choosing ingredients arelocal availability, cost, ease of addi-tion, stability, freedom from toxic-ity and salts, and nitrogen draft. Inaddition, the material should havean appropriate particle size range.Sand is the most important inor-ganic component for potting mixes.It is important to avoid sands with ahigh percentage of “fines,” particlesin the range of 0.1 mm diameter orsmaller, which can plug up porespaces. In general, the amount of

fines should not exceed 10% by weight. Forcontainer plants, at least 60% of the sand mix-ture should fall in a diameter range of 0.25 to 1mm. A broad particle size distribution tends topack excessively, as small particles slip intopore spaces surrounding larger particles. Theresult is a dense mix with low permeability, lowwater content, and high mechanical resistance toroot growth. For other components of a mix, the

far greater than that in the same soil at the samedepth in a field.

Since capillary rise is determined solelyby pore size, and pore size in turn is governed byparticle size and shape, these characteristics ofa soil have a profound effect on both the totalamount and the distribution of water and air ina potting mix. At container capacity, there is a

zone at the bottom of the container, equal inheight to the capillary rise, in which all poresare filled with water. In a coarse mix, thesaturated pores occupy a relatively shallowzone at the bottom of the pot. In contrast, a veryfine mix may be saturated with water from thebottom almost to the surface. The depth of themix in the container has no effect on the heightof the saturated zone. The depth of the mix

by a search for lightweight mixes and inexpen-sive ingredients. Now, however, changes incontainer media are made with considerationfor the principles of soil science and, in particu-lar, those pertaining to physical properties.

Physical Properties. The effect of a con-tainer on soil physical properties can be seen ina simplified comparison of water flow through asoil in a field with that through thesame soil in a pot. In both in-stances, applied water will movethrough the soil in response togravitational and matric (capillaryand adsorptive) pressures. In otherwords, the weight of water tends toforce it downward, while matricpressure, which is determined byparticle surface characteristics andthe size and shape of spaces be-tween particles, tends to attractwater. Because matric pressure isgreater in drier soil, water in thefield continues to be distributeddownward as long as there is driersoil at greater depth. When thedownward movement of water be-comes so slow that it cannot bedetected easily at the surface, thesoil is considered to be at “fieldcapacity.”

Water flow is somewhat dif-ferent in a container. When irriga-tion of containers ceases, gravita-tional pressure continues to forcewater downward. Water emptiesout of coarse pores near the sur-face, and it drips out the bottom ofthe pot. Below the bottom of thepot, of course, there is no dry soilwith fine pores to keep pullingwater downward, as there is in afield. Instead, the matric pressureexerted by the particles and poresin the soil is far greater than thevirtually nonexistent matric pres-sure in the air beneath the con-tainer. Thus, the soil holds ontowater against gravity. This “capil-lary rise” can be expressed as theheight of a column of water thatcan be held against gravity. Theheight of this water column isgoverned strictly by pore size . Aslong as the height of the column ofapplied water is greater than theheight of water the potting mix can support,water will continue to drain from the container.When the gravitational force pushing waterdownward is exactly balanced by the capillaryrise holding water in the container, water stopsdripping from the bottom of the container andthe potting mix is at “container capacity.” Thisis the maximum amount of water the soil canhold in that container. This amount of water is

Coarse Medium Fine

Volume 2, Number 1, Page 4 Winter, 1998

general size recommendation is that 60-100% ofthe particles should have a diameter between0.5-2 mm, and none should be less than 0.25mm.

For many years, most potting mixes havebeen made from sand, peat moss, softwood barkor sawdust, vermiculite, and perlite (See Table1). These can be combined to make mixes with

excellent physical properties.Some of the other materials that have

become more commonly used in containers inrecent years include: coir, a byproduct of coco-nut processing that is derived from the husks;rockwool, a spun mineral fiber akin to fiber-glass; Dialoam, another mineral product manu-factured by firing diatomaceous earth; and ex-panded shale, made by firing clay at high tem-perature. Some of these have excellent charac-

teristics either alone or in combination withother materials; others are generally used onlyas amendments (Table 2).

Chemical Requirements. Once the cri-teria for the physical properties of the pottingmix have been met, it is necessary to address thechemical requirements (for pH and fertility).Most organic amendments are highly acidic.Acid conditions can damage roots and limitnutrient availability, so the pH is normallycorrected prior to planting by adding lime or,more commonly, dolomite. The phosphorusrequirement of a potted crop can normally bemet by addition of superphosphate to the mix. Inaddition, some soluble potassium and nitrogen,as well as minor nutrients, may be supplied

prior to planting, as indicated in Table 3.The potassium and nitrogen added to the

mix help establish rapid initial growth of a plant,but are not sufficient to meet the full require-ments for these nutrients over the long haul.These requirements are usually met either byapplying a controlled release fertilizer or byirrigating with a nutrient solution containingthese elements.

The quality of the potting mix is critical tothe success of growing plants in containers. Byusing a good mix, even a distracted gardener cangrow satisfactory plants. Reliance on a poormix, on the other hand, could set civilizationback thousands of years.

Bunt, A.C., Media and Mixes for Container-Grown Plants, London: Unwin Hyman, 1988.

Handreck, K. and N. Black. Growing Media for Ornamental Plants and Turf, Kensington, Australia: University of New South Wales Press, 1994

Lindley, J., The theory and practice of horticulture; or, An attempt to explain the chief operations of gardening upon physiologicalgrounds, London: Longman, Brown, Green, and Longmans, 1855.

The author may be contacted at (530) 752-6617 or (Email) ryevans@ucdavis.edu.

For Your Information:

S e p t e m b e r ,1997-R. G. writes:About twenty-fiveyears ago, one of theCalifornia fan palmson my property wasused for target prac-

tice. About ten years ago, I filled the holes inthe bark with an aerosol foam which hardenedin place. During the past two very wet winters,the bark has become quite pitted and I fear forthis tree. Can you recommend treatment?

Answer: Although somewhat rare in na-ture, the California fan palm, known to bota-nists as Washingtonia filifera, is a familiarsight in California landscapes. This tree isnative to a small area where California, Ari-zona and Baja California meet. It is widelyused in landscape plantings along with itstaller cousin, the Mexican fan palm(Washingtonia robusta), because of its grace-ful tropical elegance and hardiness to18-20°F.Even mature trees can be uprooted and trans-planted to different sites with relative ease.Palms display very different growth charac-teristics from other trees because they aremore closely related to grasses, promptingsome horticulturists to refer to palms as “thosewacky arborescent monocots.” Palms do notform annual rings of new wood on their trunks;in fact, the only new growth is at the large

terminal bud at the top of the tree. If palmtrunks increase in diameter over the years, it isbecause the tissues swell and create air spacesbetween the cells already present. Becausethere is no potential for active growth in thetrunk of that California fan palm, there is nomechanism for repairing the wounds left bytarget practice all those years ago. The attemptto fill the holes with aerosol foam was thecorrect and perhaps only possible course ofaction. Now that secondary damage has set in,the only alternative is to clean out the wound asmuch as possible and attempt another cosmeticrepair. Some arborists have been known to useconcrete, colored to match the trunk as much aspossible, for such a repair.

November, 1997- Mrs. K. F. asks: Whatcan I do to keep my ginkgo from producingfruit?

Answer: This may sound like a silly ques-tion, unless you have ever been near a fruitingginkgo tree. The aroma produced by the matur-ing fruits challenges one’s powers of descrip-tion. Words ranging from unpleasant to putridto plainly excremental have been used to de-scribe ginkgo fruits. These words seem ratherharsh, considering the unique heritage of thisstately deciduous tree. Ginkgo biloba, or themaidenhair tree, is native to China and hassurvived since ancient times, changing very

little during its evolution. This tree is actuallyrelated to conifers and may represent a linkbetween the more primitive tree ferns andcycads and the more advanced conifers. Thefan-shaped leaves with parallel veins resemblethe fronds of the maidenhair fern, hence thecommon name of maidenhair tree. Male andfemale cones are borne on separate trees andthis is the source of woe when using this species in the landscape. There is much torecommend ginkgo as a landscape tree, how-ever, including its graceful upright shape, bril-liant yellow fall color and freedom from dis-ease and insect pests. The common practice inhorticulture is to propagate and plant only themale trees so as to avoid the problem of thesmelly fruit produced by the females. If fatehas saddled you with a female ginkgo, I fearyou have little recourse. There are hormonalsprays, such as Olive Stop, which inhibit flow-ering if applied at the correct time. Theseproducts are probably not labeled for use onginkgo and may not work anyway given itsstatus as a conifer. The Chinese have a methodfor preparing the fruits so that the nut-likekernel inside the fleshy fruit is edible and quitea delicacy, so there’s that option. Finally, themost effective alternative is to replace the fe-male with a guaranteed male ginkgo specimen(one of the few examples in nature of superior-ity of the male).

By Linda DodgeNews From the Ex(tension) Files

Volume 2, Number 1, Page 5 Winter, 1998

Summer, 1997

The 1,200 sq. ft. Urban Forestry courtyardis located on the grounds of the Department ofEnvironmental Horticulture and is surroundedby two one-story buildings. The new UrbanForestry building (south and west perimeter)houses staff of the U.S. Forest Service WesternCenter for Urban Forest Research and Educa-tion (FS) and departmental faculty in Land-scape Ecology. Departmental faculty and acut-flower laboratory are located in the build-ing on the east perimeter. The site has a 2%slope north-to-south and the soil is heavy clayloam.

The courtyard was designed to accommo-date a number of uses. It provides a travel pathto and from departmental offices and class-

Department Gets New Sustainable LandscapeBy Greg McPherson, Project Leader, US Forest Service,Western Center for Urban Forest Research & Education

Urban development has not only disconnected people from nature, buthas also disrupted the flows of energy, water, and materials through theecosystem. Designing urban forest landscapes for sustainability is onemeans of reconnecting urban residents with natural processes, while im-proving environmental quality.

The goal of the Urban Forestry courtyard project is to demonstratethrough design, management, and monitoring that sustainable landscapescan regulate energy and material flows, thereby improving environmentalquality. Design committee members Dave Burger, Jim Harding, Ron Lane,and myself are currently seeking financial support for this project, which wehope will be completed by the end of summer, 1998.

rooms to the north. Future construction of anadjacent arts complex and parking facility couldresult in the courtyard becoming an entry to theDepartment. Hence, the design needed to pro-vide a clear circulation route through the space,and a special feature or features to give it aunique identity. A space with seating wasdesired for informal interaction by small groupsof people. Limited resources for constructionand maintenance dictated need for a simpledesign that could largely be constructed bystaff and students and inexpensively main-tained by departmental staff. Most importantly,the courtyard design was intended to reflect themissions of Department and the FS throughdemonstration of innovations in sustainable

urban horticulture.The courtyard’s most dominant visual and

functional element is three cisterns in the cen-ter of the space. The cisterns are stacked,concrete pipes that together will store about3,760 gallons of runoff water from the roof ofthe Urban Forestry building. They are 4 ft. indiameter, have lengths of 16, 14, and 10 ft., andare buried in a basin that is 12 ft. deep, 10 ft.in diameter, and filled with fist-sized cobble(40% porous).

During the first few storms, water will runfrom the eaves into copper aqueducts andthrough a series of filtering devices within eachcistern. A sand filter in one cistern will beeffective at removing particulate pollutantssuch as suspended solids, lead, zinc, organiccarbon, and organic nitrogen, but only moder-ately effective at removing soluble pollutantssuch as coliform bacteria, ammonia, orthophosphorous, and copper. Large cobbles cov-ering the filter bed will reduce the erosive forceof incoming runoff. The cobbles and filter bedwill require periodic inspection and cleaning toavoid clogging. Wire mesh covering the eavetroughs will reduce deposition of debris in thefiltration system. Filtered water will drain intothe cistern through holes in the bottom of thefilter. If the rate of inflow exceeds the filter’sdrainage rate, water will overflow into thecobble basin, not the cistern.

The water quality control design objective

Section/elevation view of the courtyard landscape, designed by UC Davis landscapearchitecture student Bart Ito, depicts the location of three cisterns that will collect roofrun-off.

Specific Design Objectives• Water quality control - capture and treat the“first flush” of pollutants that wash off after thesummer dry season ends. The system should becapable of filtering pollutants from the first fivesignificant rain events (0.25 inches of rain each).

• Flood control - capture and detain on-site run-off from a 100-year event, which for Sacramentois 3.3 inches over 12 hours. The system should becapable of pumping water out of storage to in-crease flood control capacity in anticipation of alarge rain event.

• Landscape water use - capture and retain enoughwater on-site to reduce the need for importedirrigation by 80%.

• Microclimate control, building energy use, andatmospheric carbon dioxide reduction - achieve50% canopy coverage 15 years after planting,shade east and west building surfaces, and pro-vide solar access to south-facing surfaces as muchas possible.

• Green waste recycling - provide a systemwhereby 100% of the green waste can be chipped,composted, and/or mulched for reuse on the site.

Volume 2, Number 1, Page 6 Winter, 1998

Where are they ????

We wish to extendour gratitude to An-thony Tse who re-cently donated $1,000to the Harry KohlMemorial Founda-

tion. Anthony, who received his M.S. degreewith Jim Harding and his Ph.D. with WesHackett during the 1970s, now owns the Clo-ver Commercial Company, a seed and plantexport/import company based in Hong Kong.Thank you Anthony!

Michael Barbour, plant ecologist withthe Department, received $16,440 from theDivision of Agriculture and Natural ResourcesCompetitive Grants Program to work on thedevelopment of a biologically-based vernalpool classification for conservation objec-tives.

Also under this program, Jodie Holt, plantphysiologist at UC Riverside received $23,454to study factors regulating propagation of

Arundo donas (Giant reed) and implications formanagement in riparian habitats.

The Western Chapter of the InternationalSociety of Arboriculture recently awarded its1997 Award for Arboricultural Research toLarry Costello. Among several projects noted,his evaluation of street tree barriers was citedas providing valuable information that willassist parks managers in making decisionsabout dealing with tree root invasion of urbaninfrastructures. Larry is an environmental hor-ticulture advisor for San Mateo and San Fran-cisco counties.

Pamela Bone, landscape horticulturist andMaster Gardener program coordinator for UCCooperative Extension in Sacramento County,was honored by the Pesticide Applicators Pro-fessional Association as its 1996 Educator ofthe Year. Association members selected herfor her work over the past year in increasingtheir professionalism as pesticide applicators.Pam was presented a plaque and a check at the

Since graduation, Dan O'Melveny (BS,1995) has been working at High Ranch Nurs-ery in Loomis as production manager of 30acres of woody and herbaceous ornamentalspecies. Owners John and Sarah Nitta are alsoUC Davis alumni. Dan is active with theSuperior Chapter of the California Associa-tion of Nurserymen and currently serves aschapter treasurer, in addition to serving on 7committees; his favorite is the Golf Tourna-ment Committee.

Dan and his wife have a 20-month-oldson, Sam, and are expecting a child aroundChristmas. The O'Melvenys live in Davis andenjoy hiking, camping, and going to FarmersMarket. Dan can be reached via email at:dan@highranchnursery.com.

is partially met by the sand filtration system,which allows only filtered water to enter thecistern during “first flush” events. A 0.25-inchrain event generates about 5,600 gals. of run-off, of which 66% can be stored in the cisterns.The remainder will be stored in the cobble-filled basin (storage capacity of 1,800 gals).

After the “first flush” we assume that roofrunoff will be clean and can safely be storedwithout filtration. Once all cisterns are full,excess water will overflow into the cobble-filled basin. A pipe near the surface of the basinwill direct excess water under the sidewalk andinto a dry swale. The dry swale will promotefiltration of runoff into the underlying soil,while conveying excess flows to a vegetatedfilter strip located south of the courtyard. Herethe runoff will spread out and move as sheetflow across a gradually sloping vine-coveredarea. This vegetated filter strip will treat stormwater by slowing runoff velocities and filteringout sediment, nitrogen, phosphorous, and otherpollutants.

Another design feature intended to reducerunoff is porous pavement that covers about30% of the courtyard. Chunks of concretesalvaged from roads and buildings will providean all-weather surface for walking and permitplanting of grass and groundcovers in the inter-stitial space. Porous paving enhances infiltra-tion of rainfall into the soil, while recyclingconstruction debris reduces material sent tolandfills.

To meet the flood control design objective

it is necessary to store about 10,400 gallons ofrunoff on-site, assuming a 3.3-inch (100-year)rain event and a total site catchment area of4,200 sq ft. Storage provided by the cisterns(3,760 gals), cobble-filled basin (1,800 gals),dry swale (1,120 gals), and vegetated filterstrip area (4,680 gals) meet this target bystoring about 11,360 gals. A solar-poweredpump in the largest cistern will be able toempty water from all the cisterns, therebyincreasing storage capacity prior to a large rainevent.

The pump will also provide low volumeirrigation water for the landscape. The irriga-tion system will be designed and managed tominimize water lost through evaporation, over-irrigation, or other inefficiencies. Microsprayheads will irrigate groundcovers between pav-ers, bubblers will irrigate the shade trees, anddrip irrigation will be used for drought tolerantplants east of the sidewalk. We estimate thatapproximately 5,000 gallons of water will berequired to irrigate this landscape each year atmaturity. A landscape of the same size butconsisting of shrubs and trees in turf wouldrequire about 8,000 gallons more water. Hence,the planting design alone will conserve 38% ofthe water used by a typical landscape. Assum-ing full cisterns (3,760 gals), approximately75% of the total annual landscape water use issupplied by harvested runoff.

Existing vegetation consists of threeFormosan flame trees planted October 18, 1996during a building dedication ceremony by U.S.

Congressman Vic Fazio, Chancellor LarryVanderhoef, Pacific Southwest Station Direc-tor Jim Space and others.Although it makes anexcellent patio, lawn, or street tree, theFormosan flame tree is seldom seen in thelandscape. It is “solar friendly,” as well as eye-catching, provides dense shade during sum-mer, and allows ample sunlight through anopen crown during winter. Its foliation periodis synchronized with this region’s air condi-tioning period; it is relatively late to leaf outduring spring, and loses its foliage and fruit atfirst frost. Because all non-woody plant partsfall at the same time, it is a relatively easy treeto clean up after. The Formosan flame tree ishardy here, requires moderate irrigation, andappears to be relatively free from serious insectand disease problems.

Shade from the three Formosan flame treeswill meet the 50% canopy cover design objec-tive for microclimate control. After 15 years,the trees will shade about 942 sq. ft., or 79% ofthe courtyard’s landscaped area. Their shadewill reduce heat build-up by paved surfacesand cool the south- and east-facing walls,thereby reducing air conditioning loads. Vineson vertical shade structures will shade west-facing windows and walls. Fifteen years afterplanting, the three trees will sequester about450 lbs of CO

2 a year as they add new biomass.

Additionally, they will absorb approximately3.3 lbs of ozone, 0.6 lbs of nitrogen dioxide,and intercept 1.8 lbs of particulate matter fromthe atmosphere annually.

organization's recent meeting in Sacramento.

Notes From the Chair...By Dave Burger

Volume 2, Number 1, Page 7 Winter, 1998

Summer, 1997

Cooperative Extension SpecialistRichard Evans,

Profiles in Environmental Horticultureleaching of nitrogen below the root zone. Ri-chard has determined the effect of season andharvesting on the nitrogen and water require-ments of roses. Coupled with other studies hehas conducted on effects of soil aeration onroot distribution, this information could beused to improve nitrogen use efficiency.

Efficiency in commercial production op-erations requires energy conservation. Asproject manager for a greenhouse energy con-servation project funded by the AgriculturalEnergy Assistance Program, he hopes to assistgrowers make their operations more energy-efficient. Under this California Energy Com-mission program, greenhouse operators canobtain loans to install energy-efficient tech-nologies such as heat retention and shadingcurtain systems, polycarbonate or double-poly-carbonate roofs, and root zone heating sys-tems. Working with farm advisors and green-house operators, he is gathering information todetermine how much (continued, page 8)

In her second year in the Masters ofScience in Horticulture program, Lisa is happyto be following a lifelong interest in plants. Anative of Sonoma, California and member of a“non-gardening” family, much of Lisa’s freetime growing up was spent gardening in herbackyard. During summers, she worked inlandscape maintenance at Santa Rosa JuniorCollege.

Despite the fact that her interests lay ingardening, she opted to study environmentalpolicy analysis and planning, getting her B.S.degree in that field from UCDavis in 1990. “Ididn’t study horticulture because I wasn’t cer-tain what horticulture careers were out there,”she explains.

After graduation, she took a position withEMCON, a Sacramento environmental con-sulting firm, in which she performed variousconsulting services. (continued, page 8)

Carmen Garcia-Navarro,Graduate Student

Carmen originates from Montilla, a city of25,000 south of Cordoba, Spain. After study-ing agronomy at the University of Cordoba, sheaccompanied her husband, Francisco, to Daviswhere he is currently doing doctoral studies inhydrology. Undecided about future career plans,she enrolled as a concurrent student in Green-house and Nursery Crop Production, taught byHeiner Lieth. She then applied to the Mastersof Science in Horticulture program and beganclasses in fall, 1996.

A variety of work experiences in Spainkindled Carmen’s interest in horticulture and,specifically, ornamental crops. Prior to com-ing to Davis, she began graduate studies inAgriculture and Environment in Semi-AridZones in the southern coastal city of Almeria.While there, she had the opportunity to work asa volunteer with a researcher investigating theuse of native plants in the landscape. She alsoworked on a project in the Canary Islands thatlooked at water use by greenhouse roses. “Insouthern Spain, the summers are dry and avail-ability of water is poor,” she explains. Becauseof this, water conservation is an an importantissue for Spain’s horticulture industries.

Her Master’s project here in the Depart-ment addresses water conservation in the land-scape. Working with Richard Evans, she willattempt to classify ornamental species accord-ing to water needs (see Evans profile). Inspring of this year, they planted six commonlandscape species and will begin taking mea-surements of water use next summer. BecauseSpain’s climate is similar to that of California,Carmen feels confident that the knowledge shegains here will apply to landscape water useissues in Spain. Her career choice will depend,in part, on where she and her husband decide tosettle. “California is very nice,” she admits,“but it’s possible that we will return to Spain.”

Since joining the departmental faculty in1986, Richard’s research interests have en-compassed several areas of horticulture, in-cluding postharvest care of cut flowers, green-house and nursery production, and landscapesoils and irrigation. Currently, his work fo-cuses on water, energy, and nutrient conserva-tion—both in the landscape and in commercialproduction operations.

Because nutrient waste is economicallyand environmentally costly, efficient use offertilizer by plants is a high priority for com-mercial flower growers. Richard conductsongoing studies to investigate ways to helpgrowers prevent nutrient waste by maximizingnutrient uptake. Several factors influence aplant’s capacity for nutrient uptake. Large rootsystems, for example, provide extensive sur-faces for extraction of nutrients. One currentproject investigates increasing the surface areafor absorption of nutrients by innoculatingcontainer soils with mychorrhizal fungi (mi-crobes that form a symbiotic relationship withcertain plant roots and occur naturally in land-scape soils). In this way, the surface area of theroot system of container-grown plants can, hebelieves, effectively be increased. “It’s sort oflike helping the plant to grow additional roots,”he explains, “and the more roots a plant has,the more water and nutrients it will be able toextract from the soil.” He points out thatmychorrhizae are especially good at taking upphosphorus, thereby reducing the amount ofthis nutrient that is lost through leaching. Re-ducing phosphorus runoff reduces the surfacecontamination of groundwater that results inalgal bloom and other harmful environmentaleffects.

Additional factors affecting nutrient up-take are root distribution and plant demand fornutrients. In greenhouse roses, shallow rootsystems limit uptake of nitrogen and result in

Lisa Bruni, Graduate Student

Volume 2, Number 1, Page 8 Winter, 1998

Cooperative ExtensionU.S. Department of AgricultureUniversity of CaliforniaOakland, CA 94612-3560

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GPSusan Imboden, Managing EditorEnvironmental Horticulture Dept., University of California, One Shields Ave., Davis 95616-8587Phone: (530)752-8419; Fax: (530)752-1819; E-mail: growing@ucdavis.edu

of the total energy used in the state is used ingreenhouses, the annual cost to heat green-houses, the most energy-efficient methods forheating greenhouses, and future trends of green-house heating and cooling technologies andenergy use and cost in California.

Another project, funded by the SlossonFoundation, addresses the need for water con-servation in the landscape. While the widely-used practice of applying crop coefficients toestimate water requirements works well forplanning irrigation of turf and agronomic crops,it falls short when used to estimate the waterneeds of ornamentals in the landscape. Be-cause landscape plantings are commonly mixedand contain plants with varying leaf canopies,the range of water requirements may be broad.These and other factors present a need forwater use guidelines that take variations intoaccount.

Toward this end, Richard is attempting todevelop a method for classifying landscapeplants by relative water use. His idea is thatcommercially grown container plants may beusable as indicators of likely water use of thoseplants in the landscape. Plants could then begrouped according to water use. High waterusers such as Viburnum tinus or Forsythiaintermedia, for example, would be grouped withplants like Cercocarpus betuloides (Mountainmahogany), which uses less water. This methodwould allow for modification of irrigation in

existing landscapes and better design of futurelandscapes.

As an extension specialist, Richard con-tinues to make up-to-date information on hisand other projects available to growers. Hisphilosophy is that, while educating growersand helping find solutions to practical prob-lems is important for California agriculture, itis equally important to respond to those indus-tries with the greatest need: “I think thatExtension should focus a little more on provid-ing information on minor nursery crops likesunflowers, strawflowers and native species,for which information is lacking.” He is amember of the Association of Specialty CutFlower Growers, a national organization thatinforms growers on the production and market-ing of field and specialty flower crops.

Currently he teaches Management of Con-tainer Media, an undergraduate course offeredhere in the Department. For more informationabout this course or the above projects, youmay contact him at (530) 752-6617, orryevans@ucdavis.edu.

(Evans, continued)

Over a period of 5 years, she evaluated soil andgroundwater analytical data to assess contami-nation and pollution risk and assure contami-nation compliance at solid and hazardous wastelandfill sites. She also performed propertytransfer assessments and facility complianceaudits for private manufacturing industries and

governmental agencies. But working with plantsremained her real interest, so she returned toschool to pursue the horticulture field. “I’vealso always wanted a master’s degree,” sheadds.

Her project with Richard Evans looks atinnoculating flowering container plants withmychorrhizae to reduce phosphorus leaching.She hopes to determine whether mychorrhizalinfection can occur in container media and, ifso, whether this treatment will reduce leachingand increase uptake of phosphorus.

Several career possibilities are on the ho-rizon. Perhaps she and her husband will start asmall business such as a seed company ornursery. Managing a nursery, doing research,or working in an arboretum or botanical gardenappeal to her as well. “I’ll be happy working inany of these areas,” she says. “So whateverhappens, happens.”

(Bruni , continued)