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Notes from the Arnold Arboretum

Perennials forLow Maintenance GardeningPart I

Herbaceous perennials have a reputation for being difficult togrow. Many of them are, and numerous favorites of long stand-ing such as the Hardy Aster, Carnation, Delphinium, Lupine,Bee Balm, Phlox, and others require time and effort if good re-sults are to be achieved. Some must be divided frequently tomaintain robust vigor, others have to be staked or supported,some have serious insect and disease problems, and manysimply do not live up to the promise of permanence so fre-

quently heralded in the catalogs.The Arnold Arboretum constantly receives inquiries for lists

of dependable, hardy trees, shrubs, and ground covers, but fewpeople seem aware of the relatively long list of perennials thatadapt themselves well to shrub borders or foundation plantings.In fact, there are enough of these perennials so that the old styleperennial border could easily come back to favor today if em-phasis were placed on selecting those varieties which combinethe virtues of a long life with relative indifference to neglect.

This past autumn the Practical Gardening Class at the Ar-nold Arboretum selected as a class project the renovation of apart of the Low Maintenance Garden at the Case Estates. For

many years this garden has demonstrated that certain slow-growing shrubs can be combined with herbaceous perennialsto make an attractive display. A number of the shrubs hadgrown large, and we decided to remove some of these to ob-tain space for displaying more of the perennials desirable inlow maintenance schemes. Selection of the best varieties re-

ceived much attention, and this article is an outcome of thatselection.

In this discussion a deliberate attempt has been made to

enumerate the disadvantages of many favorite garden plants,and this must be done if one is to end up with a list of the

easiest types to grow. Catalogs of nurserymen have a decided

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tendency to emphasize the advantages of all their offerings;for after all, nurserymen have to make a living, too. Most

popular books on perennials do list the drawbacks involved, butthis is frequently lost among lengthy descriptions and culturalformulae. Some of the plants described here have few faults;others will be dismissed in a seemingly harsh manner. Keepingthe above objectives in mind, it is hoped that this will not causeundue alarm to that dedicated group of advanced gardenerswho take delight in growing the more difficult plants to perfec-tion.

Achillea - Yarrow, Milfoil, SneezewortThis genus of the Daisy family is for the most part easy to

grow and possesses the endearing ability to live on in spite ofconsiderable neglect. Almost all adapt well to poor garden soils.In fact, average to poor soil which is somewhat on the dry sideis best for them, as rich moist conditions will lead to weak

growth and inferior flowers. The ability to withstand droughtin open sunny locations and the finely textured, fern-like foliagewhich remains in good condition throughout the growing seasonare other points in favor of this group. Perhaps their worstfault is a tendency to spread rapidly by basal shoots, and amplespace must be allotted to them. A. ptarmica (Sneezewort) andits various cultivated forms such as A. ’The Pearl,’ A. ’Perry’sWhite,’ and A. ’Snowball’ have definite invasive tendencies anddo best when divided every year. For this reason, despite theirvalue as cut flowers, they cannot be recommended here.

A. fzlipendulina (Femleaf Yarrow) and its varieties and hy-brids are decidedly the best for use in low maintenance typeplantings. The author’s favorite is a relatively new varietycalled ’Moonshine’ which has a neat, compact habit and is wellfitted for the front of the border. It grows to a height of onlyeighteen to twenty-four inches and staking is not necessary asis sometimes the case with the taller typical form of A. filipendu-lina. The silvery grey foliage contrasts with the sulphur-yellowflowers, which are borne over a long period of time in flat-toppedumbel-like inflorescences. Beware the glowing descriptions ofcatalogs which describe this and other varieties as "bloomingfrom June to the very end of September." This condition can

only be achieved by faithful attention to the removal of thefaded flowers. Few indeed are the perennials which are "everblooming" when left to their own devices.A close second to A. ’Moonshine’ is A. ’Coronation Gold,’ a

taller and more robust form also with yellow flowers. A. ’Gold

26 iPlate’ and A. ’Parker’s Variety’ are occasionally available. They,too, fit into the above description and well-grown specimensoften have flower heads up to six inches across. All varietiesin this group provide good cut flowers which, if picked early,can be dried for winter arrangements.

A. millefolium (Common Yarrow, Milfoil) is widely natural-ized in this country and is occasionally grown in medicinal herbgardens, but it is weedy and hardly worth the trouble in theborder. The same holds for A. millefolium f. rasea a form withpinkish red flowers. Several improvements have been derivedfrom this, which can be recommended, and we see offered suchvarieties as A. ’Fire King,’ A. ’Cerise Queen,’ and A. ’CrimsonBeauty’ which have flowers ranging from rosy-red to very deeppink. These grow to a height of one and a half feet and forma rather dense mat of growth which is best divided every thirdyear. Apart from this, they require little additional attention.

A. ageratifolia and A. tomentosa are sometimes offered incatalogs for use in the front of the border. These are at bestrock garden subjects, and of little use elsewhere.

Aconitum - Aconite, MonkshoodPlants which prefer to be left alone and which at the same

time do not outgrow their welcome must be considered valu-able. When they also display attractive glossy foliage through-out the season and provide conspicuous blue flowers which areexcellent for cutting, they deserve to be widely grown. Atten-

tion is focused from time to time on the poisonous nature ofthe Monkshoods. Although it is true that no portion of the plantshould be eaten, it is unlikely that human beings would find oc-casion to taste either the leaves or the roots of this plant. Thatexcellent ground cover, Lily of the Valley, produces rather con-spicuous red fruits which are also poisonous, but this is seldomheld against it when planting time comes.

Monkshoods are sometimes planted near Delphiniums to

provide a similar vertical effect in late August and Septemberafter the Delphinium fades. They resent hot summers and dobest in partial shade in slightly acid soil rich in humus. The

taller types often have to be staked to look their best, so choiceof a shorter variety is advisable where maintenance will be

minimal.A. fischeri with violet-blue flowers stands sturdy and erect at

two and a half to three feet, whereas its variety A. fischeri var.wilsoni towers to six to eight feet and requires support. A.

napellus, the English Monkshood, is quite variable with flowers

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ranging from blue to violet and its foliage is more finely dividedthan the others. It, too, may require support.The best of several cultivars of A. napellus is A. ’Bressing-

ham Spire’ and although it is difficult to find, it is in the trade inthis country, and well worth the effort to locate. The flowersare a deep violet-blue. The three-foot terminal spikes are fol-lowed by several secondary spikes from halfway up the stem.These prolong the flowering period by a few weeks and do notdetract from the upright "Gothic" form of the plant. As to stak-ing, one well-known English writer states that the stems are"strong enough to resist a tornado."

Amsonia - AmsoniaAmsonia tabernaemontana is an American plant native from

Pennsylvania to Florida and Texas. It has been neglected bygardeners and yet it is one of the easiest plants to grow thatwe have.

It is insect and disease free, slow-growing and never invasive,does equally well in moist or dry soils, is easily transplanted,never needs staking, does well in sun or partial shade (perhapsa little better in shade), and the foliage remains in excellentcondition throughout the growing season. The tough stems aresaid to be quite resistant to wind and the plant will thrive inseaside gardens.

Perhaps this long list of virtues will pardon Amsonia for notbeing the showiest plant in the border when in blossom. How-

ever, the steel-blue flowers in terminal panicles are most at-

tractive when at their best in May.The plant usually attains a height of three to four feet and

a few nurseries list a "dwarf variety" of A. tabernaemontanawhich grows from two to three feet tall. This latter is probablynot a variety at all, but another native species, A. ciliata, whichis suitable for growing at the front of the herbaceous border.

Anchusa - Alkanet, BuglossSome plants are best admired in other people’s gardens; per-

haps this is one. A. azurea the Italian Alkanet blooms for a

long period and has true-blue flowers, a color which is alwayswelcome. It is not particular as to soil, provided it is welldrained. However, while it requires no staking it is coarse andbristly, and as it grows to a height of five feet, it is suited to theback of the border only. After about the second year the plantsinvariably start to deteriorate. It also has a habit of seeding inand taking over territory not assigned to it, thus becoming a

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nuisance in a small garden. A. ’Royal Blue’ is a dwarf three-foot cultivar now available in this country. It appears to be avast improvement and if one must have Alkanet, this is the oneto try. It should not require staking, but will have to be dividedafter the second or third year if it is not to peter out.Anchusa mysotidiflora is listed in many catalogs. This is

properly Brunnera macrophylla (see below), a much more

worthy garden subject than the true Alkanet.

Aquilegia - ColumbineUnless one can provide excellent drainage, Columbines are

apt to be transitory in nature and of no value to those who havelittle time to continuously replace plants. They should be tried,however, for if they find conditions to their liking they seed inover large areas on their own, and seedlings in any unwantedplaces are quite easy to control. Many of the fancy long-spurredvarieties show a decided tendency to degenerate to all sorts of"mongrels" when seeding occurs, but A. ’Copper Queen,’ A.’Crimson Star,’ A. ’Snow Queen,’ and A. ’Rose Queen’ have thereputation for reproducing surprisingly true.

Columbines have another bad feature which must be takeninto consideration if space is limited. Often they suffer fromleaf miners which are difficult to control and when the briefshow of flowers is gone, one is left with a not-too-beautiful dis-

play of debilitated foliage.There are a large number of species and cultivated strains

to choose from. The alpine sorts are difficult and should beavoided by the novice. A. ’Mrs. Scott Elliot’ and A. ’McKana’sGiants’ are old favorites of vigorous growth and fairly easy cul-ture.

Artemisia - Artemesia, WormwoodSoft silver or gray foliage can be used in a number of ways

in the perennial border, either to provide notes of accent or ascontrast to such colors as blue, red, pink, or yellow. Of the

plants which possess this characteristic, Dianthus (Pinks andCarnations) are difficult to grow in the Boston area and otherplaces where summers are hot and dry; Santolina is not reliablyhardy; Lavandula officinalis, the true Lavender, and its varietyL. officinalis var. nana and various hybrids will survive, but inexposed situations they may require winter protection; Stachysolympica and Cerastium tomentosum have excellent gray fo-

liage and are hardy, but both have definite invasive tendencies.One variety of Artemisia is reliably hardy and very suitable

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for planting in low maintenance schemes. This is a cultivatedform of A. schmidtiana var. nana known as ’Silver Mound.’ Itforms a rounded, mound-like plant about one foot high anda foot and a half in diameter. One failing is that if planted intoo rich a soil, growth is lush and the mound of foliage flopsand opens in the middle. It would be best to consider this plantwhere hot, sunny conditions prevail and soil conditions are

relatively poor.A. albula ’Silver King,’ and A. albula ’Silver Queen’ are fre-

quently offered in catalogs. They form a mass of silver grayleaves on stems two to three feet tall and provide excellent driedleaves for winter arrangements. However, they are disappoint-ingly short lived if not divided annually and they cannot toleratewet winters.

Aster - Hardy AsterHardy Asters can be given very little attention here, and the

gardener who has a minimum of time is advised to stay awayfrom this group. The well-known Michaelmas daisies of En-

glish gardens are all cultivated varieties of our own native NewYork Aster, A. novi-belgii. Annual spring division is almost anecessity if good shape is desired. So, too, is staking and cut-ting back in midsummer.Numerous other species and varieties are available and some

of the dwarf cultivars are excellent, both for the perennialborder and for the rock garden, but they all should be dividedevery second or third year.

Astilbe - AstilbeAstilbes suffer from the same affliction as the Asters, they need

to be transplanted every few years to maintain their vigor. Thisis unfortunate because the flowers of the modern Astilbe hybridscan be obtained in a number of very pleasing pastel shades.They have become an almost indispensable feature of watersideplantings and thrive where soils are moist and rich. Partialshade is beneficial where moist conditions cannot be relied uponthroughout the summer.

Astilbes would be my personal choice over Asters, Chrysan-themums, Carnations, or Delphiniums if I could grow only onegroup of perennials which require extra attention. This is due

largely to the attractive feathery panicles of flowers which

range in color from purple to red, pink, or white. Some of thebest Astilbes offered today are cultivars of A. x arendsii pro-duced by George Arens of Ronsdorf, Germany. They usually

Fig. 8: Low maintenance garden at the Case Estates. Photo. P. Bruns.

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grow to about two feet tall, but under ideal conditions they mayreach three and a half feet.

A. ’Federsee’ (rosy red) and A. ’Irene Rotseiper’ (lilac rose)are of robust growth and better able to withstand dry conditionsthan most. Other good cultivars are A. ’Etna’ (garnet red), A.’Fire’ (intense salmon red), A. ’Garnet’ (deep rose), A. ’RedSentinel’ (deep brick-red), A. ’Rheinland’ (bright pink), and A.’Vesuvius’ (fiery red).

Baptisia - False or Wild IndigoIt has been suggested that B. australis (the False Indigo)

might be desirable for those who have difficulties with Del-

phiniums and Lupines. If grown specifically for this purposeit may prove to be a rather poor substitute, but the plant is ofvalue in many other ways.

It does not require a rich soil, has no serious insect or diseaseproblems, will live on for a number of years in one spot, andwill not become invasive. Although it will tolerate full sun,best results are obtained in partial shade. The indigo-blue flow-ers are borne in terminal racemes on stems reaching three tofour feet. After flowering in May, attractive inflated black podsdevelop, which are useful in dried arrangements. Baptisiaaustralis is also a member of that group of plants whose foliageremains in good condition all summer.

B. tinctoria (the Wild Indigo) has small yellow flowers fol-lowed by small black pods. It is better suited for wild areasthan flower borders.

Brunnera - Dwarf Anchusa, Siberian BuglossBrunnera macrophylla (Syn. Anchusa myosotidiflora) is a

very easy plant to grow where conditions are shady and the soilis moist. It is extremely hardy and tolerates much neglect. Ofparticular value are the branched racemes of tiny true-blue star-like flowers which are darker than those of Forget-me-nots. Theplant blossoms during April and May and can be used for aground cover in shady places. It can also be used individuallyand in small groupings in the flower border.

Ceratostigma - Blue LeadwortCeratostigma plumbaginoides is most frequently listed in

catalogs as Plumbago larpentae. It is a desirable little plantwhich produces clusters of light blue flowers during late sum-mer and early fall. The plant is hardy if it is given sunny con-ditions, rich soil, and excellent drainage.

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Six to eight inches is its maximum height, and when left un-disturbed a single plant will form a clump twelve to eighteeninches across. In the fall the leaves turn to a bronze-green andthis color intensifies with cooler weather.

Chrysanthemum - Hardy Chrysanthemum, Pyrethrum, ShastaDaisy

This very large group of the Daisy family contains a greatnumber of subjects which are nearly indispensable in the her-baceous border, but there are several problems when consider-ing them in a planting designed for a minimum of maintenance.

The "Hardy Mums," by far the most widely planted of thegroup are best if divided every year (or at least every otheryear). Similarly, Cushion varieties should be divided everyother spring. Winter protection is often necessary as the rootsystems are shallow and subject to heaving during alternateperiods of freezing and thawing. Chrysanthemum coccineum(the Painted Daisy or Pyrethrum) and varieties of C. maximum(The Shasta Daisy) must also be divided every second or thirdyear, and not all cultivars are dependable over a wide range ofconditions.

Whole books have been written which describe the manyvarieties of Chrysanthemum. This will not be attempted heredue to their limited value in the low maintenance garden.

Cimicifuga- Snakeroot, Bugbane, Cohosh ’

These are rather stately plants five to eight feet tall which,when well established, can be left alone for many years. Thesmall white flowers are produced on long racemes well abovethe shiny compound leaves. They are best used as single speci-mens in the herbaceous border but adapt themselves equally wellto massing at the edge of a pond or stream. A moist soil witha high organic content will suit them best.Two species are commonly available. C. racemosa (Black

Snakeroot or Bugbane) will, under ideal circumstances reach aheight of nearly eight feet although it grows from five to sixfeet under normal conditions. It blooms from late June to earlyAugust, the flowering period being prolonged by the produc-tion of lateral branches. C. simplex, the Kamchatka Bugbane,reaches a maximum height of three feet and blooms in lateSeptember and October.

Clematis - ClematisThe numerous climbing woody varieties of Clematis are de-

manding when it comes to the proper conditions for good growth.

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This is not so with the herbaceous kinds, but few amateur gar-deners know of their value. Although not as showy as theclimbers, they bloom over a long period during the summerand, once established, become permanent additions to the gar-den. They require rich, well drained soil and benefit from oc-casional applications of lime. Full sun or partial shade is satis-factory.

C. integrifolia ’Coerulea’ has large porcelain-blue bell-shapedflowers. Although it attains a height of only two feet, the stemshave a tendency to flop if not supported. Where this cannot bedone, allow plenty of room so that the plant will not crowd itsneighbors. When given a moderately moist situation, or ifwatered during dry spells, it will bloom from June to August.

C. recta var. mandshurica is valuable for its white flowers interminal and axillary clusters during June and July. It is veryvigorous and best seen as a single specimen near the back ofthe border. Again, one should allow ample room for this vig-orous grower.

C. heracleaefolia var. davidiana (sold as C. davidiana) flow-ers later than the above; its blue flowers are welcome in Au-

gust and September. The fragrant tubular flowers are producedin terminal and axillary clusters on stems two and a half tothree feet high. The compound foliage has a decidedly coarseappearance and it would be best not to feature this plant in themost prominent part of the border.

Coreopsis - TickseedA few members of this large genus of the Daisy family are

excellent for the low maintenance border, but many lack com-

plete hardiness or are best seen naturalized in a wild garden. Allare of value for their showy yellow flowers which last wellwhen cut.One of the best is the Thread-Leaf Coreopsis, C. verticillata.

It makes dense clumps about two feet tall, and although indi-vidual flowers are small, they are freely produced among thefinely textured leaves. It blooms from June to September. An-other good feature of this plant is the ability to withstand drysoil conditions. C. verticillata ’Golden Shower’ is about six inchestaller and has larger deeper yellow flowers.

C. grandiflora is perhaps the showiest of the group, but toooften it behaves as a biennial and for that reason cannot beconsidered here. C. lanceolata is similar in appearance and of

greater value. The showy two-foot plants will withstand muchneglect if planted in a sunny location.

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The best tall species to grow is C. tripteris. It has slightlyfragrant flowers one and a half inches across, which are paleyellow with a disk that turns brown or purple. It blooms in

August, and although plants may reach six feet at the rear ofthe border, staking is not required and established clumps neednot be disturbed for many years.

Delphinium - DelphiniumFew plants can approach the modern strains of D. elatum for

their bold effect in the border, but this is a decidedly finickygroup and cannot be guaranteed as long-lived under normal con-ditions. One new strain called D. ’Connecticut Yankees’ maywell be the answer for those who would like to grow the Del-

phinium but cannot cater to its many whims. These come inan excellent color range, and form well-branched bush-typeplants seldom over thirty inches tall and resembling speciesDelphiniums in habit. These were tried at the Arnold Arbore-tum for the first time last summer and although they weregiven almost no attention, excellent results were obtained. Un-doubtedly they are more permanent than taller Delphinium hy-brids, but we do not know at this point how long they will lastunder our conditions.

Dianthus - Pink, CarnationThis is another large genus which cannot receive much at-

tention here. Some varieties are not very hardy and the groupas a whole is disappointing throughout most of this countrywhere summers are hot and dry.A notable exception is the Cheddar Pink, D. gratianopolitanus,

which understandably, is more frequently listed under the syn-onym D. caesius. This has admirably survived exposed condi-tions in the Ground Cover Plots at the Case Estates. Its onlyfault is that it forms such a thick mat that portions die out fromtime to time and division must be resorted to. Plants form a

dense, low mat of foliage with small fringed flowers in shadesof pink borne on six-inch stems. D. ’Rose Queen’ is an inter-

esting selection with double bright-rose flowers.

Dicentra - Bleeding Heart, Lyre Flower, Dutchman’s BreechesFor permanence the best of this group is D. spectabilis, the

Bleeding Heart or Lyre Flower, which is a true aristocrat of theborder for the short period when it is in bloom. A well-estab-lished plant forms a large clump with arching sprays of pinkheart-shaped flowers in late May and June. It prefers a rich

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soil with a high organic-matter content and results are alwaysbest if light shade can be provided. Specimen plants are prefer-able to groupings because they take up a lot of room, and the fo-liage has a tendency to die down in the hot part of the summer,leaving a large gap in the border. This would be unfortunatewere it not for the fact that Gypsophila paniculata (Baby’sBreath) and its varieties can be used effectively nearby. By thetime the Bleeding Heart is ready to disappear Gypsophila is

ready to fill in the gaps. An alternative is to use the emptyspaces for the planting of annuals. D. spectabilis var. alba isoccasionally available. This has a very delicate constitution andis really not worth bothering with.

D. eximia is of great value for its long flowering period fromMay to August. The dissected leaves are grayish blue, remainattractive throughout the growing season, and make a good con-trast to the pink flowers. Under normal circumstances it willhave to be divided every third or fourth year. D. eximia ’Bounti-ful’ is a relatively new cultivar said to be the result of a crossbetween D. eximia and D. oregana. Flowers are a deeper pink,almost fuchsia-red. All during the summer a few flowers areproduced, but in the autumn it blooms almost as freely againas it did in the spring.

D. cucularia, Dutchman’s Breeches, requires woodland con-ditions and is not a fitting subject for the herbaceous border.

’

To be continued

ROBERT S. HEBB