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Vol. 44 No.1 Winter 1983-84 arno ~a

Amoldia (ISSN 0004-2633) is published quarterly in Page spnng, summer, fall, and wmter by the Arnold 3 Walnuts for the Northeast Arboretum of Harvard University. Edward Goodell

Subscriptions are $12.00 per year; single copies $3.50 20 Propagating Leatherwood: A Lesson in Second-class postage paid at Boston, Massachusetts. Humility Postmaster: Send address changes to: Peter Del Tredici Amoldia The Arnold Arboretum 25 When Is a Pine Not a Pine? The Arborway B. June Hutchinson Jamaica Plain, MA 02130 29 The River Birch Copyright © 1984 President and Fellows of Harvard Anne Carlsmith College. 32 COLLECTOR’S NOTEBOOK Eileen J. Dunne, Editor

Peter Del Tredici, Associate Editor 34 BOOKS David Ford, Graphic Designer

Front cover photo~ Cone of the umbrella pme (Sciadopi- tys verticillata). /. Back cover Needles of the same species. Al Bussewitz photos.

Walnuts for the Edward Goodell Northeast

The walnut has been held in high esteem of walnut trees is poison to all plants within since ancient times. The Romans considered its compass...." While it is true that walnut it preeminent among nuts and gave it the species (and some hickories) produce a toxic name jovis glans (Jupiter’s nut), from which chemical identified as juglone (5-hydroxy-l, the modem taxonomic name for the walnut 4-napthoquinone) the actual phytotoxic ef- genus, juglans, has been derived. Several fect varies considerably depending on / 1 ~ the species of walnuts are popular throughout different levels of tolerance among plants, (2) the Western World today, both for their fine whether or not the roots of adjacent plants wood and flavorful nuts. Large commercial contact the walnut root, and (3) the amount walnut industries exist in the Mediterranean of air present in the soil. Although the black region of Europe and on the west coast of walnut probably has the most notorious the United States (primarily California, with reputation for allelopathy (as destructive 200,000 acres). Although walnuts are grown chemical interaction between plants is throughout much of this country, they have known), this phenomenon has been increas- never been grown widely in the Northeast. ingly documented throughout the plant Several types can be grown here, however, world, and it is worth noting that tall fescue including the Persian walnut ( juglans regia grass (Festuca arundinacea Schreb.) exerts L.), the black walnut (J. nigra L./, the butter- a similar deleterious effect on walnuts (Riet- nut (f. cinerea L.~, and the Asian walnuts (J. veld 1981/.( . ailanthifolia Carr, j. mandshurica Maxim., Toxic juglone is oxidized from hydroju- and j. cathayensis Dode), all of which have glone, a nontoxic substance found in all nutritiou6, flavorful nuts. We will explore in parts of the walnut plant. Oxidation of the following the merits of these types and hydrojuglone occurs in the presence of air their cultivation in the northeastern United and during contact between walnut roots States and adjoining areas of Canada. and the roots of other plants that contain Any talk of walnuts must begin by ad- oxidizing compounds. Hydrojuglone is dressing the toxic effect walnuts are said to highly reactive, however, and in the con- exert on neighboring plants. Pliny the Elder, tinued presence of air quickly breaks down in the first century A.D., wrote, "the shadow into harmless substances. Root-to-root con- tact is therefore the only means by which damage can occur unless plants are in soil that is poorly drained, and therefore poorly aerated. Black walnuts / Juglans nigra/ ripening on the tree. Al Bussewitz photo. Tomatoes, apples, most ericaceous plants, 4

and many conifers are known to be adversely regia is often called the English walnut, pre- affected (MacDaniels 1976 and 1980). The ef- sumably because it was introduced here by fects of walnut toxicity are noticeable either English colonists. However, it is not grown as flagging, wilted leaves (in tomatoes) or extensively in England. Most horticul- more commonly as a long-term gradual turalists call it the Persian walnut in defer- stunting of the plant. On the other hand, ence to its origin. many plants are not affected at all, including The Persian walnut is native to the area numerous grasses and vegetable crops, many between the Carpathian Mountains in east- legumes, some Rosa and Vitis species, and ern Europe and the Himalayan Mountains in most native hardwoods. This immunity may northern India, a swath across the Balkan result from either a root zone that does not Peninsula, Turkey, Iran, Afghanistan, and coincide with that of the deep-rooting wal- the adjoining areas of the USSR. A geograph- nut or an actual tolerance to the toxic prop- ically disjunct population occurs in northern erties of juglone. China (Icongraphia Cormophytorum According to current information we can Sinicorum 1972 and Meyer 1911). Wild be optimistic about the prospects of success- plants are normally found in mixed broad- fully growing a wide range of plants in as- leaf forests, along stream banks, in valleys, sociation with walnuts. A general precau- and on mountain slopes (Komarov 1936). In tion is advised: locate susceptible plants sheltered valleys, where it thrives, Juglans with a long life span outside the eventual regia may grow 20-35 m high with a root zone of walnuts. This is urged espe- straight, upright trunk and a large, spreading cially in wet soils, where the toxic effect is crown. Normally the wood is purplish more likely. However, during the initial pe- brown, hard, and satin-smooth and shiny riod of growth walnuts can be grown near when polished. The nuts of wild trees gener- even susceptible plants (as root spread is nar- ally have thin shells and large kernels. Vari- row and contact therefore avoided). For ex- ous subspecies have been proposed based on ample, at an orchard spacing of 6 meters on- nut shape, growth habit, and geographic ori- center black walnut can be interplanted gin (Komarov 1936 and Rehder 1940). with vegetable crops, small fruit, and/or Persian walnuts have always been valued Christmas trees for at least 10 years. trees within their native and naturalized range. The timber is used in Europe for fine woodwork and veneer. Trees that are suc- Persian Walnut cessful in the northeastern United States have come from colder regions of the The common commercial walnut is the species’ range, Romania, Hungary, Czecho- Persian walnut, fuglans regia. This was the slovakia, Poland, USSR, and Germany, where only walnut known to the Ancient Romans. they have traditionally been popular yard juglans regia came to Rome from Persia via trees. Outstanding selections are currently Greece, and Roman conquerors spread it being propagated and tested for commercial throughout southern Europe to England. orchards in these countries (Shreve 1981/. On the North American continent Juglans Most selections of Persian walnuts cold 5

Carpathian walnuts, /Juglans regia) above, origi- nated m the Mountams of southern Carpathian called walnut trees and known Poland. Carpathian for their cold hardiness, became widely es- tablished from British Columbia to Nova hardy enough for North America derive from Scotia and are still being selected for their seed collected in the Carpathian Mountains hardiness, nut qualities, and yields. of southern Poland. Reverend Paul Crath, a Reverend Crath’s introductions were not native of the Ukraine, worked as a Presbyte- the first cold-hardy Persian walnuts brought rian missionary in that region between 1924 to North America, however. Since the late and 1936, after having been ordained a 1700s German immigrants had been bring- minister in Canada. Reverend Crath was ing hardy Juglans regia seed from their keenly interested in the Juglans regia trees homeland to Pennsylvania and farther west. he found commonly growing in Poland, The descendants of these seedlings are on where minimum winter temperatures could the average less tolerant of cold than the reach -40°F. He believed that some of these Carpathian walnuts, but several are among trees would succeed in cold areas of North the most hardy and productive cultivars. America. Through arrangements with Other promising introductions have been members of the Northern Nut Growers’ As- made from the Russian Ukraine, the sociation and the Wisconsin Horticultural Himalayan Mountains, and northern China. Society, he sent back several tons of seed A great deal of potential still exists for col- (Devitt 1953). The resulting trees, often lecting genetically superior seed from the 6 1

cold-temperate areas where the Persian wal- (personal communication from L. H. Wil- nut has been grown since antiquity. moth, July 21, 1982). Regardless, the overlap In a 1936 letter Reverend Crath described in staminate and pistillate flowering times the trees of the Carpathian region: would rarely be enough to ensure a good We examined 79 walnut trees in and around Cos- crop. Several cultivars are notable for their seev. The age of the trees varied from 15-100 self-fruitfulness, but even these seem to years. Trees 30 years old and over were from 60 to benefit significantly from cross-pollination 75 feet tall, and from I to 3 feet in diameter. Of with another cultivar. the 79 trees, 3 trees were the only damaged by In the North the most common cause of frost of 1929 (45 degrees below zero) (Rahmlov 1962). crop damage among Persian walnuts is their tendency to produce leaves and flowers be- Experience on this continent has shown that fore the possibility of late frosts has passed. with site conditions a Per- good cold-hardy In Ontario, Persian walnuts are most suc- sian walnut tree will rapidly grow to the size cessful within 20 km of the Great Lakes, and of a tree. shape very large apple The where the cool spring climate delays vegeta- canopy is globe shaped and dense, the bark tive growth. The gradual onset of winter and the roots When pale gray, deep. fully there also ensures a more complete dor- some Persian walnuts tolerate dormant, may mancy and less damage from cold. Under op- temperatures between 30°F and 40°F with- timal growing conditions Persian walnut out damage (O’Rourke 1969).). seedlings bear fruit within 4-8 years and However, injury can occur at much grafted cultivars within 2-5 years. A few higher temperatures ( -13°F) if mild seedlings from a Russian source have been weather precedes a drop in temperature. Per- reported to flower in their second year sian walnuts will grow on a variety of soils, (McDaniel 1978). Pistillate flowers are gen- but poor drainage invariably renders them erally produced several years before stami- more susceptible to winter injury. High nate flowers. In their eighth growing season, vigor and good nut production require a fer- productive cultivars may bear 0.03-0.06 m3 tile, nearly neutral soil and room for exten- of nuts. Large trees may yield 0.2 m3 (Grimo sive root development. 1979). Reverend Crath reported harvests of Persian walnuts are monoecious. The 45-115 kg from mature, native Carpathian staminate catkins expand from lateral buds trees. Persian walnuts bear crops annually, of the previous season’s growth. The clusters though weather conditions have a consider- of 1-3 (occasionally 4-5) pistillate flowers able effect on yields. Individual trees are are borne at the tips of the current season’s known to continue bearing for more than shoots. Pistillate flowers, and the nuts that 100 years. subsequently develop from them, normally Juglans regia is unique among walnuts in appear only on growth originating from the that its nuts fall free from the husks at ripen- terminal buds. On some cultivars the lateral ing time. This feature, combined with easily shoots also bear flowers, which increases cracked shells, places Persian walnuts their yield. It is unclear as to whether all among the more desirable of nuts. The ker- Persian walnut trees are self-fertile or not nels can usually be extracted in large or 7

whole pieces from the relatively thin-shelled A single Persian walnut tree will eventu- nuts by hand. The kernels are high in protein ally occupy a space 15 m in diameter but can (20 percent) and fat (60 percent) and account be planted at half that spacing to hasten or- for 40-60 percent of the total nut weight. chard production. Seedlings may be grown to On the west coast of this country, Persian bearing age for evaluation on only 3-meter walnut trees are valued for their appearance spacings. Seedlings of good parentage are and are grown in yards, parks, and along likely to yield one tree in ten "exceptional streets. In the cold areas of eastern Europe enough to be made permanent" (Society of and northern China, they have long been Ontario Nut Growers). The hole to which valued for their nuts and timber also. Now, the seedling is transplanted must be larger however, selections hardy in the northeast- than the spread of the root system. A kilo- ern United States offer nuts and timber of a gram of bonemeal mixed into the planting quality similar to that of the European and soil (preferably one year in advance) is a re- Chinese types. quirement for healthy growth. Any injured roots must be trimmed off before planting, and the remaining roots carefully spread Persian Walnuts Growing when the soil is sifted over them. It is best to Many Persian walnut growers in the North place the root collar at, or slightly below, are cultivating the seedlings of superior trees ground level. When the seedling is in place, in the hope of finding improved types. Plants the soil must be tamped down and watered grow readily from seeds sown in the fall, or thoroughly. A trunk guard, or a piece of after a relatively short (6-8 weeks) artificial woven wire coated with white latex paint, cold-moist treatment. They will also germi- will protect against sunscald and rodents. nate satisfactorily after dry storage if they The young tree will not be able to compete are first soaked for several days in clean with weeds and will respond favorably to water that is changed daily. Spring planting mulch as it grows. is best, about 4 cm deep with a light mulch. Persian walnuts must not be fertilized in Cans or wire mesh placed over the seeds will the first year, and only in the early spring protect them from rodents, crows, and thereafter. These trees use large amounts of pheasants. nitrogen and phosphorus: one recommenda- Planting sites for Persian walnuts must be tion is 0.2 kg of 20-10-10 granular fertilizer chosen carefully. Adequate soil drainage is per 3 cm of trunk diameter until the trunk important, as moist soil delays the onset of diameter reaches 15 cm. After that the ap- winter dormancy, causing freeze damage plication rate is doubled, up to a maximum (splitting) to the trunk. The soil must allow of 11-13 kg per tree with a 5-10-15 formula- deep roots to penetrate 1.5 m, have an ap- tion. This tends to reduce vegetative growth proximately neutral pH (pH 7) and be fertile and increase nut production. enough to grow a good cover crop. Adding Pruning requirements are minimal. Many dolomitic lime or fertilizer, or planting a Persian walnuts independently exhibit the legume in the preceding year is recom- ideal conical or dome shape, requiring only mended to improve the soil. the removal of branches that are dead, rub- 8

bing, or malformed. A high, clear trunk can Persian walnuts have much to recom- be maintained for lumber production. mend them. They are attractive landscape Persian walnuts grown in the Northeast trees, having pale bark and a dense, round are potentially susceptible to several pests crown. Several cultivars are hardy at average and diseases (Payne and Johnson 1979), in- minimum temperatures as low as -30°F if cluding the husk fly, the coddling moth, the soil and air drainage are adequate. butternut curculio (insect larva), an an- thracnose fungus, a bacterial blight, and a bunch disease causes numerous (which Black Walnut shoots to emerge in close proximity). Choos- ing disease-resistant plants, removing leaves The black walnut is a native American from beneath the trees after leaf fall, and tree that grows wild throughout eastern timing sprays carefully will provide success- North America except most of New York ful control. Trees exhibiting a bunching pat- and New England. It is among the most val- tern in the branches should be removed en- ued cabinet-wood and veneer trees on this tirely, as should trees that sucker exces- continent. A commercial cracking industry sively from the lower trunk. The latter is an in the Midwest is supported by wild col- indication of either bunch disease, walnut lected nuts. The nuts are valued for their blight, a genetic lack of hardiness, or wet flavorful kernels and their shells, which are soil. used in the manufacture of a multitude of During the ripening period, squirrels useful products. poach nuts before they have fallen, but a Soil conditions are a major influence on smooth trunk collar (0.5 m high) will keep the growth of black walnuts. These trees do them out of the treetops as long as no access best on soils that have a neutral pH, are fer- is provided by an adjoining tree or building. tile, and have adequate water. They grow Even so, the nuts must be harvested fre- slowly on wet lands, shallow topsoils, and quently if squirrel populations are dense in those that are acidic and infertile. Sapling the immediate area. black walnuts are intolerant of shade and are Treatment after the harvest involves dry- generally suited to sites where white ash ing the walnuts in an airy location for about ~Flaxinus americana grows well (Fowells five days. During this period the kernel loses 1965). its milky texture, becoming crisp and sweet. While truly wild black walnuts are un- Like most foods, walnuts sold commercially common east of the lower Hudson River do not compare in taste to those grown at Valley, they have often been planted as yard home. Storing walnuts is best accomplished trees and sometimes have become either in-shell, using rodent-proof aerated naturalized. containers in an unheated room, or by freez- The black walnut tree is large and ing the kernels alone. Nuts with well-sealed straight-trunked, with an open spreading shells usually retain their kernel quality crown. The pale green pinnately compound until the next harvest season. Frozen kernels leaves cast a dappled shade. An identifying will store for years with very little change in characteristic during the dormant season is quality. the stout, upright branchlets. These resem- 9

Black walnuts /~uglans nigra)/ Nuts can be harvested until the lower sec- tion reaches prime veneer log size (55 cm).). ble the branches of white ash, but the wal- Trunk diameters of orchard-grown trees can nut branch arrangement is alternate instead be twice that of similarly aged trees grown in of opposite. Black walnuts normally have timber plantations, presumably because the deep tap roots, which when established superior care and the wider spacing of the permit them to coexist with groundcovers trees in orchards are more favorable for girth and allow them to tolerate some degree of increase. Careful pruning is required in the drought. These trees are also tolerant of fire early years to produce a straight log free of and smog (Duke). Their growth rate is highly large knots. dependent on site and soil conditions and The black walnut, the preferred commer- genetics; 1 m per year in height is possible. cial walnut, has a distinctive flavor, which is The ornamental value of the black walnut not diminished by cooking. The kernels con- tree lies in its stately form and the dappled tain approximately 20 percent protein, 155 shade it affords. The leaves fall relatively percent carbohydrate, and 60 percent fat, as early without spectacular coloration. The well as small amounts of mineral nutrients decaying husks leave an amber stain on and vitamins A and B. hands, clothing, and concrete. Black walnut Unfortunately, obtaining this nutritious trees with an unbranched trunk at least 3 m nut meat can be a frustrating experience. In high will produce both timber and nut crops. fact, removing the nut from its messy, stain- 10

ing husk and then extracting the kernel from tion of desirable cultivars for New England. its hard shell is hardly worth the effort with The most important characteristic for this most unselected black walnuts. This is not region is a capacity to ripen nuts in growing the case with several cultivars selected for seasons of less than 180 days. Those that their ease of cracking. have generally received high ratings when Cracking qualities depend on shell thick- grown in northern latitudes are listed on ness and the internal shell structure. The page 16. kernel cavities of most unselected black walnuts have many partitions and deep in- Growing Black Walnuts vaginations, whereas those of named cul- tivars usually have fewer, and kernels can be Black walnut seeds and seedlings are extracted in large pieces. Also, the nuts of widely available from commercial and state cultivars are usually 25 percent kernel, 5 nurseries. In fact, enough are sold each year percent more than the average for unselected to establish about 2880 hectares of planta- seedlings. tions (Funk 1979). Seedling trees rarely equal Grafted cultivars may begin bearing nuts cultivars in nut quality or productivity. A within two or three years, though substan- homeowner desirous of a single tree is better tial production must wait until trees are past off purchasing a grafted cultivar. For larger 10 years of age. Crop yield is more closely plantings, seedlings are more cost-effective, correlated with crown size and trunk diame- and some may turn out to have improved ter than age. A vigorous tree is the best in- characteristics for the Northeast. Seeds or surance of a plentiful nut crop. The biggest seedlings should be obtained from parent challenge in managing walnut trees for nut trees with desirable traits: climatic adapta- production is to maintain regular annual tion, superior productivity and nut quality, yields. Even the annual variation in yield is and perhaps timber form. A large, well-filled irregular. Providing adequate sunlight, nu- nut produces a larger seedling. Cold strat- trition, and water and controlling pests ification for 120 days results in the most minimizes yield variations but does not prompt germination. Fall planting usually necessarily eliminate them. satisfies this cold requirement. Seeds sown Black walnut cultivars have been selected in fall tend to germinate more quickly and in primarily for ease of cracking and productiv- greater numbers than those sown in spring. ity. Very little information is available on The hulls need not be removed before plant- their performance in New England, how- ing the nuts. About 50 percent of unhulled ever. Although over 500 cultivar selections seed will germinate. A higher germination have been identified by the Northern Nut rate can be achieved by hulling the nuts, Growers’ Association, most have not been placing them in a container of water, and widely propagated or tested. The perfor- discarding those that float. A well-filled nut mance reports that do exist vary consid- will sink if the float test is given before ap- erably, depending on climatic, cultural, and preciable drying has occurred (within 3 days site factors. Observations in New York, of hulling). Michigan, and Ontario offer the best indica- Black walnuts are planted in the same way 111

as Persian walnuts. The results of a study of to a lesser extent, nitrogen supply. Weeds various methods used to protect the nuts should be controlled with mulch for at least from squirrels favored placing fresh cow two years (preferably three or four) after manure over sown seeds as an "effective, planting. biodegradeable repellent" (Williams and Favorable soil conditions are crucial for Funk 1978). Due to the fact that they germi- healthy growth and nut production. The soil nate in relatively low numbers, black wal- must be well drained. It should allow roots nuts should be seeded at approximately to penetrate at least 1.5 m. A near neutral pH twice the desired density. Planting nuts should be maintained with dolomite appli- 10 cm apart produces tall, straight seedlings cations. Trees bearing nuts have high nitro- that are to or easy graft transplant. It is ad- gen and phosphorus requirements. About 0.55 visable to several plant seeds wherever a kg of 10-10-10 fertilizer per centimeter of tree is desired. Later (anytime within three trunk diameter is recommended for ade- growing seasons), all of the surviving seed- quate nutrition. lings must be removed except the one show- Another way of improving the soil’s fertil- ing the best vigor and form. ity is to interplant black walnuts with In general, direct seeding is better than nitrogen-fixing plants. Russian olive . transplanting. Black walnuts develop a deep (Elaeagnus umbellata), black locust ^ taproot quickly, which is often damaged (Robinia pseudoacacia European alder (AI- in transplanting and is a setback for nus glutinosa), and hairy vetch (Vicia vil- the entire tree. After three to four years, losa) have all proved to enhance black wal- trees in a plantation tend to be about the nut’s growth rate, especially on less than same size regardless of whether they were ideal sites (Funk 1979 and Ponder 1981).( . grown from seed or transplanted (Funk These fast-growing nitrogen-fixing species 1979). shelter the young walnuts from wind and re- A wide hole with room for the roots to duce weed competition somewhat. Addi- spread is best. Many labor-saving planting tionally, the walnut growth is forced up- methods have been devised for transplanting ward, which reduces pruning requirements. large amounts of black walnuts, but the The general pruning recommendation for primary consideration is to ensure that the black walnuts is to maintain a single domi- roots are spiraling. The survival and growth nant leader and evenly spaced lateral of transplanted seedlings is directly related branches. The bottom section of trunk can to their size. Only year-old seedlings with a be developed as a valuable veneer log by stem diameter greater than 5 mm should be pruning the branches when they reach 3 cm planted. in diameter. Pruning can be done up to half It is important to provide favorable condi- of the tree’s total height without adversely tions for young black walnut trees. Trees affecting the growth rate. This method keeps that are vigorous when young are usually the knots small and confined to the central vigorous when older also. The most critical core of the veneer log. Bey (1979) provides factors affecting growth rate are soil mois- further information on pruning for timber ture, weed competition, wind exposure, and, production. Planting black walnuts in frost 12

pockets increases the need for pruning, be- about one week. The dry nuts are best if cause the terminal buds are more likely to stored in a cool, airy location, and rodent- suffer freeze damage, resulting in many proof containers are advisable. competing lateral shoots. Cracking by hand is usually done with a To my knowledge black walnuts growing hammer or screw vise. Pouring hot water in eastern Massachusetts have not been over the nuts and allowing them to steep 24 seriously afflicted with diseases or insects. hours helps to soften the shells, which pre- Husk-fly maggots frequently infest the husk vents then from shattering when cracked. in early fall, turning it into a mass of black The wire cutters used by electricians can be slime, but a study has shown no correlation employed to extract the kernels. Kernels fro- between husk maggots and nutmeat quality zen in plastic bags keep well. (Gibson and Kearby 1976). However, some pests can affect nut production (Payne and The Butternut Johnson 1979). Walnut curculios can damage tender growth and cause some nut loss. Re- The butternut, another native American moving infected nuts that drop prematurely tree, has a more northerly geographic is the best control. Anthracnose fungus in- distribution than its cousin the black fections of foliage and fruit cause nuts to fill walnut. The butternut range occupies much poorly. Wet weather conditions mean more of New England and the St. Lawrence River severe infections. Anthracnose-resistant Valley of Quebec, west to southern cultivars will retain healthy foliage longer Minnesota, and south to Missouri and and produce better crops. Fungicide sprays southern Appalachia. But rarely is it more during spring provide successful control. than an occasional component of forest Apparently, black walnuts can be infected stands. Butternut occurs primarily on with walnut bunch disease without showing stream banks or valley slopes where the soil the normal brooming symptoms. Instead, it is moist but well drained. However, it is appears as empty or dark and shriveled nuts. known to grow better than black walnut on There are no reliable controls for this dis- dry, rocky soils, especially those of ease. Infected trees should be destroyed. limestone origin (Fowells 1965). The entire husk and enclosed nut fall The butternut tree is short, averaging 13 m during or shortly after leaf fall. The nuts that high. Thick branches generally begin low fall early are less likely to be well filled. on the trunk and rise into a broad, open Freshly fallen nuts are the best ones to col- crown. Butternut bark is light brown or gray lect. At this stage the hulls separate easily and becomes deeply ridged with old age. The and the kernels have not had time to become compound leaves resemble those of black stained and lose flavor. Rubber gloves (not walnut but are quite hairy and sticky in vinyl) will protect hands from the corrosive, comparison. The same rust-colored, sticky staining juices. The hull of a freshly har- pubescence also covers leaf petioles and vested, well-filled black walnut will shuck young branchlets in their first year’s growth off with one tap of a rubber mallet. The and is especially noticeable on the nut hulled nuts can then be washed, and dried husks. Another identifying characteristic is either on newspaper or in a wire basket for the leaf scar. In black walnut it is notched 13

Butternuts ~Juglans cmerea)(

traction and nut size. Cold storage is advis- able, but nuts in shell reportedly keep a year without a downy fringe, whereas in butter- or more under cool, ventilated conditions nut the leaf scar is not notched but does have (personal communication from Stephen a downy fringe. Breyer, July 15, 1982). Butternuts are among the most hardy Jug- Nut production begins within six or seven lans species, surviving -40°F within their years from seed (McDaniel 1979), but butter- natural geographic range. In spring bright nuts never seem to yield as well as black green staminate catkins droop from the walnuts. Six bushels of nuts in hull is an ex- basal portion of the previous season’s ceptionally high yield from a mature tree, growth. The 5-8 pistillate flowers are borne and large annual variations in yield are to be on spikes at the end of new growth. The expected. Butternuts may produce nuts for single or clustered 5- 7 cm egg-shaped nuts more than 70 years. ripen in early fall. A thin adhering husk en- Native Americans extracted oil from closes the deeply ridged, thick shell. The crushed butternuts by boiling them in water. kernels, which are sweet and oily, are gener- In New England the flavorful kernels are ally regarded as the best among walnuts for still combined with maple sugar in candy. flavor but are normally impossible to extract Like that of the sugar maple tree, the sap of in large pieces. A few cultivars exist, se- butternut also makes a good syrup, but more lected primarily for their ease of kernel ex- boiling is required to thicken it. The husks 144

and inner bark yield a true dye. During the However, the modern authority on the wal- Civil War, the backwoods Confederate nut family, W. E. Manning (1978) places the troops were sometimes dressed in homespun Asian walnuts in a separate subsection on ’uniforms’ of butternut-dyed cloth, and they the basis of their differences in embryo de- became known as butternuts (Peattie 1966). velopment. In the field Asian walnuts can Butternut wood accepts a high polish and supposedly be distinguished from the but- is easily worked. It was once a favorite for ternut by their notched leaf scars, but the carriage interiors, because of its combina- difference is not readily discernible. Asian tion of beauty and lightness, and is still val- walnuts bear nuts in hanging racemes that ued. In Wisconsin, one of the major states are usually much longer than butternut supplying butternut lumber, it is second clusters. The Asian walnuts cross readily only to black walnut for its economic value. with other juglans species, and fertile hy- The wood is also rot resistant. brids may result, especially in crosses in- Relative to other nut trees, butternuts are volving the butternut. quite short-lived, beginning to decline in 75 Confusion exists about the correct scien- years. This inherent trait is compounded by tific name for the Japanese walnut and its susceptibility to two fungal diseases: the smooth-shelled variety called the heartnut butternut dieback (Melanconis juglandis~ and (Rehder 1945). The name formerly accepted the butternut canker (Sirococcus clavigig- for the Japanese walnut, J. sieboldianaa nenti juglandaceareum/. These factors, (Maxim.), can no longer be used because it along with pollution and elimination of has already been given to a fossil plant. The habitat, threaten the butternut throughout current consensus, with which Manning much of its range. concurs, is to name the Japanese walnut J. In the colder regions of northeastern ailanthi folia Carr and the heartnut J. ailan- North America, growing butternuts may be thifolia var. cordiformis (Maxim.) Rehd. the only way to harvest high-quality nuts. The Japanese walnut is a common forest Cultivars are available with nuts that can be tree of mountain regions in Japan (Sargent cracked easily and flavorful kernels that can 1894), whereas the heartnut is a cultivated be removed in large pieces. These trees are variety (Ohwi 1965). The two are identical in fast growing with broad canopies offering habit and foliage, differing only in nut dappled shade. characteristics. The Japanese walnut is rough and pitted like a butternut. The heartnut is and val- The Asian Walnuts smooth, heart-shaped, ued for its ease of cracking and kernel ex- Three walnut species are native to east Asia: traction. Seedlings of both Japanese walnut the Japanese walnut / J. ailanthi folia Carr), and heartnut may produce either type of nut. the Manchurian walnut /J. mandshurica The Manchurian walnut is native to Maxim.), and the Chinese walnut (J. northern China, Korea, and the Amur River cathayensis Dode). These are closely related region of Siberia. It may grow to 20 m tall, to the American butternut and are often in- either in mixed forests (in valleys and cluded in the same subsection of Juglans. floodplains) or isolated on the gravelly soils 15

beside mountain streams. Its growth habit and racemes of 6-17 nuts are similar to those of the other Asian walnuts. The nuts vary in shell structure, are round to elon- gate, 2.7-5.5 cm in length, and (like butter- nuts) have a sharply ridged to relatively smooth shell. The Manchurian walnut is ex- tremely hardy, on a par with the butternut. It is in cold areas of the cultivated USSR, Heartnut /juglans ailanthifolia var. cordiformis)( Europe, and the Canadian plains. No nut- producing selections have been made in this 90 kg harvest from the cultivar called ’OK’. country. The Lithuanian magazine Musu Five to 15 nuts occur in pendant racemes. A Sodai in 1976 reported a selection hardy to recently ripened soft husk may be twisted -40°F that blooms first on old wood and off by hand, leaving only a few fibers at- again in 2-3 weeks on new growth (personal tached to the shell. Even if the nuts are not communication from Victor Vircau on July husked immediately, the kernels are less apt 19, 1982). to be stained than are those of black wal- The Chinese walnut is a close relative and nuts. perhaps only a geographic race of the Man- Heartnuts usually have well-sealed shells churian walnut. It grows in the highlands of and good keeping qualities. They can gener- central China and is considered less hardy. ally be split into two heart-shaped halves Mature plants at the Arnold Arboretum sur- either by tapping the shells while holding vive temperatures as low as -10°F without the nuts on edge or by using a channel-lock noticeable damage. tool. A certain degree of drying can enhance Because of its ease in cracking, the the cracking process. The kernels have a heartnut ( J. ailanthi folia var. cordiformis mild flavor similar to that of the butternut has received the most attention among the but not quite as highly regarded. The kernels Asian walnuts. In its native Japan it is culti- are about 50 percent oil and 25-35 percent of vated in orchards and marketed. Heartnut the total nut weight. tre.es grow rapidly (to 6 m in eight years) and The heartnut and butternut apparently bear nuts at five years of age. They report- cross-pollinate readily, resulting in a fertile edly adapt to a wide range of soils, from sand and remarkably vigorous hybrid known as to clay, and some will grow in zone 4 (avg. the buartnut ~J. cinerea x j. ailanthifolia var. min. temp. -30°F) (Metcalf 1980). However, cordiformis). Several selections combine the heartnuts seem to be adapted to a maritime hardiness and flavor of butternuts with the climate similar to Japan’s, because they suf- ease of cracking and potentially greater fer damage from early fall freezes and late yields of heartnuts. Two different cultivars spring frosts. are needed for pollination and subsequent With the exception of certain cultivars, nut production. heartnuts are said to bear nuts freely but In the Asian walnuts and their hybrids, we rarely heavily. Gellatly (1966) reported a have nut-producing, ornamental shade trees 16

for the North. Several features give them an Persian Walnut overall exotic appearance: long hanging cat- The following descriptions are drawn kins ; large, compound, seemingly tropical primarily from those of Ashworth (1969),), foliage; and pendant strings of nuts. The Brooks and Olmo (1972), and Grimo (1979).). stout branches and broad top provide a dap- With the exception of ’Hansen’, which is pled shade. Asian walnuts thrive on a variety highly acclaimed, little agreement exists as of soils. Most are hardy thoughout zone 5 to how they should be ranked. and some in zone 4. The disease primary ’Broadview’ originated in British Colum- threat to these walnuts is the bunch disease. bia from seed brought there by a Russian immigrant from the Black Sea region. Opin- ions differ about its kernel flavor. The nuts, which are medium to in Walnut Cultivars large, ripen Sep- tember at about the same time as McIntosh A considerable number of commercial nurs- apples. In cracking quality they approxi- eries supply walnut cultivars. Many of mately equal those of ’Franquette’, the stan- them are quite small, however, and managed dard commercial walnut cultivar in Califor- on a part-time basis. As their stock may be nia. The nuts are 46 percent kernel and keep small or sold out, it is best to place orders well in storage. ’Broadview’ is considered one-half year or more before spring planting. one of the most productive cultivars. The Nurseries usually sell scionwood for do-it- original tree withstood temperatures as low yourself propagation, and some offer custom as -30°F, but subsequent reports indicate propagation services. marginal hardiness in zone 5. Walnuts are considered difficult to propa- ’Hansen’ is probably the most favored, gate vegetatively. The most common means cold-hardy Persian walnut cultivar. It was is by grafting. Among the most successful introduced in 1952 from northwestern Ohio. methods are: a modified side-graft, 75-80 The original tree may be over 100 years old percent (Funk 79); a root cleft-graft, 75 per- and presumably is of German origin. ’Han- cent (Groenwald 1981) ; and greenwood bud- sen’ has the ability to fruit on lateral as well ding, 90 percent (Davie and Davie 1977). I as terminal shoots, resulting in early (2 years have used the sprouted-seed grafting method after grafting) and numerous nuts. The trees described for chestnuts (Jaynes 1980) with remain small and are resistant to disease and fair results. A warm post-graft environment husk maggots. The nuts mature early and will enhance the success of all grafting are relatively small but at 60 percent have methods. Heartnuts and Persian walnuts can one of the highest percentages of kernel. The be layered (Gellatly 1966 and personal round shells are thin and smooth. The ker- communication from Stephen Breyer, July 5, nal flavor is mild and sweet. ’Hansen’ is an- 1982), and both rooted cuttings (Shreve other self-fertile cultivar. 1975) and root cuttings of black walnut have ’Holton’ is a promising cross between proved successful ~Jaciw and Larsson 1980).( . ’Hansen’ and ’Broadview’. Preliminary ob- Purchasing walnut cultivars is the best route servations indicate that it combines the best for most people. qualities of both parents. Like ’Hansen’ it is 177

a hardy and a precocious bearer of nicely Other cultivars that have received high shaped and flavored nuts, which resist dam- rating for northern areas are ’Bums’, age from husk maggots. The ’Broadview’ ’Snyder’, and ’Thomas’. Less-tested black parentage is evident in the vigor of the tree walnuts with potential value for New En- and its relatively large nuts. gland include: ’Beck’, ’Sparks # 127’, ’Sparks ’McKinster’ is a Crath seedling originating # 147’, and ’Davidson’. The latter three have form the Columbus, Ohio, area. The nuts are been selected in Iowa for their ability to large (48 percent kernel) and have a good flower on lateral as well as terminal shoots. flavor. This fairly productive cultivar, which (This characteristic leads to earlier and self-pollinates, is well adapted to Ohio and heavier yields.) favored in the lower peninsula of Michigan. ’Somers’ is a Crath seedling from the same source as ’Greenhaven’. ’Somers’ consis- Butternut bears attractive nuts. tently high-quality Butternuts tend to be difficult to propagate The kernel constitutes more than 55 usually and are not in high demand, so nurseries of the and its oil content is percent nut, may not have stock on hand. A few of the more than 64 percent. The early ripening of better-known and available cultivars are: ’Somers’ (early to mid-September) often pre- ’Ayers’, ’Booth’, ’Chamberlin’, ’Craxezy’, cedes husk-maggot damage. ’Creighton’, ’Joy’, ’Kinnyglen’, ’Kenworthy’, ’Love’, ’Van Sickle’, and ’Weschcke’. All of " these are to be cold in the ’ Black Walnut reported hardy North. Over 500 black walnut cultivars have been selected and named. The following are Heartnutt among those that have received high ratings when grown in northern locations. The de- Most heartnut cultivars were selected scriptions are compiled from reports by primarily before attention was diverted to Brooks and Olmo (1972), Funk (1979), Mac- the introduction of Carpathian walnuts. The Daniels (1974 and 1941), and Zanger (1969). following cultivars are most likely to be ’Sparrow’, from Illinois, has a very thin available. The descriptions follow Campbell hull, which is easy to remove. It cracks well ( 1981 Gellatly (1966), and McDaniel (1979).). and has a high kernel content (29 percent) ’Brock’ is a relatively recent and promising and very good flavor. Its anthracnose- cultivar from Pennsylvania. ’Etter’, also resistant foliage is retained late into the fall. from Pennsylvania, has excellent cracking The nuts ripen fairly early and vary in size qualities and is 33 percent kernel. It may be according to site conditions. resistant to bunch disease. ’Etter’ seedlings ’Emma K’, from Illinois, has a thin shell, a are often equal to or superior to their parent. high kernel content, and excellent flavor. It ’Fodermaier’ nuts are 37 percent kernel but bears nuts regularly in southern Ontario but rarely crack in whole pieces. Even so, it is a may not fill all of them. It appears to be re- highly regarded heartnut. ’Fodermaier’ seed- sistant to both anthracnose and aphids. lings generally produce good quality nuts. 188

’Marvel’ and ’Rival’ are both progeny of Gellatly, J. V. 1966. "Heartnuts." 57th Annual Report ’Fodermaier’. Other heartnuts of value in- of the Northern Nut Growers’ Assoczauon: 103-111. clude ’Canoka’, ’OK’, ’Rhodes’, ’Schubert’, Gibson, K E , and W H. Kearby. 1976. "Black Walnut and ’Wright’. Meat Quality in Relation to the Presence of Husk Fly Maggots in the Husks." 67th Annual Report of the Northern Nut Growers’ Associatzon. Buartnut 109-13. Gnmo, E. 1979."Carpathian (Persian) Walnuts." InNut Tree Culture in North I was not able to discover any nurseries that Amerzca, edited by R. A. Jaynes. Hamden, Connecticut. Northern Nut offer buartnut trees. The grafted following Growers’ Assoczauon. cultivars may be available as scions or by Groenwald, M. R. 1981. "Use of Walnut Cleft Graft to custom propagation: ’Corsan’, ’Dunoka’, Produce Walnut Trees for Nebraska Plantings."" and 72nd Annual Report of the Northern Nut Grow- ’Fioka’, ’Hancock’, ’Leslie’, ’Mitchell’, ers’Assoczatzom 62-67. ’Wallich’. Iconographza Cormophytorum Sinicorum 1972. Pek- ing. In Chinese. Jaciw, P., and H. C Larsson. 1980. "Vegetative Propa- gation of Black Walnut." 71 st Annual Report of References the Northern Nut Growers’ Assoczatzon: 70-74. Jaynes, R. A. 1980. "Chip Budding Sprouted Chestnut Ashworth, Fred L. 1969. "Butternuts, Siebold (Japanese) Seed." 7Ist Annual Report of the Northern Nut Walnuts, and Their Hybrids." In Handbook of Growers’ Assoczauon North Amencan Nut Trees, edited by R. A. Komarov, Vladimir L. 1936. Flora of the U.S.S.R. Lenin- Jaynes. Hamden, Connecticut: Northern Nut grad : Botamcal Institute of the Academy of Sci- Growers’ Associauon. ences of the USSR (Available from National Bey, C. F. 1979. "Prumng." In Nut Culture in North Techmcal Information Servzce, U.S. Department America, edited by R. A. Jaynes Hamden, Con- of Commerce, Springfield, VA 22151./.( necticut : Northern Nut Growers’ Association. MacDamels, L. H. 1980. "Further Observations on the Brooks, R., and H. Olmo 1972. Register of New Fruit Toxicity of Black Walnut on Tomatoes and Some and Nut Vameues. 2nd edition. Berkeley: Uni- Other Plants." 71 st Annual Report of the North- versity of California Press. ern Nut Growers’ Assoczauow 112-26. Campbell, R. D. 1981. "Ten Years of Expenence with . 1976. "Walnut Toxicity: An Unsolved Prob- Nut Trees." 72nd Annual Report of the Northern lem." 67th Annual Report of the Northern Nut NutGrowers’Associauon 152-54. Growers’ Assoczauon. 114-22. L. Davie. Davie, B., and 1977. "Budding Persians, Black . 1974. "Black Walnut Testing." 65th Annual Walnuts, Heartnuts, and Butternuts on Black Report of the Northern Nut Gzowers’ Assocza- Walnut Rootstocks." 68th Annual Report of the tzon: 68-71. Northern Nut Growers’ Association. 108-110. . 1941. "Nut Growing in the Northeastern Devitt, L. K. 1953. "Late Rev. Paul C. Crath." 44th An- States."Arnoldia, 1: 45-64. nual Report of the Northern Nut Growers’ As- MacDaniels, L. H., W. T. Johnson, and E. J. Braun. 1975. sociation. 80-84. "The Black Walnut Bunch Disease Syndrome."" Duke, J. A. "/uglans mgra L." Economic Botany Labora- 66th Annual Report of the Northern Nut Grow- tory, U.S. Department of Agnculture, Beltsville, ezs’Assoczauon~ 71-87. Maryland, n.d. McDamel, J. C. 1979. "Other Walnuts, Includzr.g But- Fowells, H. A. 1965. Silmcs of Forest Trees of the U.S. temut, Heartnut, and Hybrids." InNut Tree Cul- USDA Handbook 271. Washington, D.C.: U.S. ture in North America, edited by R. A. Jaynes. Government Printing Office. Hamden, Connecticut: Northern Nut Growers’ Funk, D. T. 1979. "Black Walnuts for Nuts and Assoczatzon. in Timber." In Nut Tree Culture North America, . 1978. "Amateur." Nutshell, 32(2) 6-10. ’ edited by R. A. Jaynes. Hamden, Connecticut: Manning, W. E. 1978. "The Classification Within Ju- Northern Nut Growers’ Association. glandaceae. Annoys of the Missouri Botanical 19

Garden, 65: 1058-87. Williams, Robert D., and David T. Funk. 1978. "Cow Metcalfe, R. E. 1980. "A Three-Year Heartnut Study."" Ma;aure Deters Rodents from Stealmg Seeded 71st Annual Report of The Northern Nut Grow- Black Walnut." 69th Annual Report of the ers’ Associatiom 50-52. Northern Nut Growers’ Association: 43--48. Meyer, F. N. 1911. "Agricultural Explorations m the Zanger, T. G. 1969. "Black Walnuts As Nut Trees." In Fruit and Nut Orchards of Chma. U. S. edited . Depart- Handbook of North Amencan Nut Trees, ment of Agnculture Bureau of Plant Industry by R. A. Jaynes. Knoxville, Tennessee: Northern Bulletm 204 Washington, D.C.: U.S. Depart- Nut Growers’ Association. ment of Agriculture. Ohwi, Jisaburo. 19G5. Flora of Japan. Edited by Fred- enck G. Meyer and Egbert H. Walker. Washing- ton, D.C.: Smithsoman Institution. O’Rourke, F. L. S. 1969. "The Carpathian (Persian) Wal- nut." In Handbook of North Amencan Nut Trees, edited by R. A. Jaynes. Knoxville, Tennes- see : Northern Nut Growers’ Association. Payne, J. A., and W. T. Johnson. 1979. "Plant Pests." In Nut Tree Culture m North Amemca, edited by R. A. Jaynes. Hamden, Connecticut: Northern Nut Growers’ Association. Peattie, Donald Culross. 1966. A Natural History of Trees. 2nd edition. Boston: Houghton Mifflin. Ponder, F. 1981. "Some Guidelines for Selecting Black Walnut Planting Sites." 72nd Annual Report of the Northern Nut Growers’ Association: 112- 19. Rahmlow, H. J. 1962. "Distribution of Carpathian Wal- nuts by the Wisconsin Horticultural Society."" 55th Annual Report of the Northern Nut Grow- ers’Association 125-28. Rehder, Alfred. 1945. "Notes on Some Cultivated Trees and Shrubs, II." Journal of the Arnold Ar- boretum, 26:472. . 1940. Manual of Cultivated Trees and Shrubs. New York: Macmillan. Rietveld, W. J. 1981. "Significance of Allelopathy in Black Walnut Cultural Systems." 72nd Annual Report of the Northern Nut Growers’ Associa- tion : 117-34. Sargent, Chailes Sprague. 1894. Forest Flora of Japan. Boston: Houghton Mifflin. Shreve, L. W. 1981. "Walnut and Almond Improvement Programs in Romania and Hungary." 72nd An- nual Report of the Northern Nut Growers’ As- sociation: 22-26.

. 1975. "Black Walnut Propagation Techniques Used in the Tree Improvement Programs at Kan- sas State University." 66th Annual Report of the Northern Nut Growers’Association: 148-55. Society of Ontario Nut Growers. "Persian Walnuts."" Newsletter of the Society of Ontario Nut Grow- ers. Niagara-on-the-Lake, Ontario, Canada: Soci- ety of Ontario Nut Growers, n.d. Edward Goodell is a frequent contributor to Amoldia. Propagating Peter Del Tredici Leatherwood: A Lesson in Humility

It is often assumed that because I work in just like a cowhide, and would answer the pur- the greenhouses of the Arnold Arboretum, I pose of one admirably. The color of the bark is a very pale brown. I was much interested in this should be able to solve any plant-propaga- shrub, since it was the Indian’s rope. Frost said tion that comes With all that problem along. that the farmers of Vermont used it to tie up their heat and light, the reasoning goes, you fences with. should be able to make dead sticks sprout. The tensile of the bark of Unfortunately, technology is not always the great strength most effective solution to the difficulties leatherwood has been noted by nearly all bo- tanical writers - before and after Thoreau that arise with plants. This fact was brought - who have discussed the home to me rather dramatically recently plant. None, have so memora- in attempting to determine the seed-germi- however, presented quite nation requirements of Dirca palustris, the ble a description as the late Edgar Anderson, Atlantic leatherwood. former dendrologist of the Arnold Ar- This beautiful little shrub is native to the boretum and long-time botanist at the Mis- souri Botanical Garden: east coast of North America, from New Brunswick to Florida and east to the Missis- Delicate though the flowers may be, the species is sippi. In the wild, Dirca tends to form dense well deserving of its popular name as anyone will thickets in the forest understory, growing find who attempts to gather the flowering twigs without a sharp knife. The branches are surpris- best in moist areas that have a high lime- ingly limber and the bark is tough and strong. stone content. David Thoreau tracked Henry One can actually tie the twigs in bow knots. If the plant down in its native haunts in one attempts to snap off a branch quickly, the Brattleboro, Vermont, on September 8, 1856: wood itself may break and separate from the bark. It may even come away altogether, leaving the ... for the first time I see growing indigenously startled flower-gatherer with a perfectly bare twig the Dirca palustris, leather-wood, the largest on in his hand and on the bush, dangling like an the low interval the brook. I notice a bush by empty glove, the bark with its flowers and leaves there seven feet In this form it is somewhat high. still intact. hke a quince bush, though less spreading, its leaves are broad, hke entire sassafras leaves; now Horticulturally, Dirca is noteworthy for to turn It has beginning yellow. remarkably reasons other than its bark, not the least of thick bark and soft white wood which strong which is that it produces bright yellow flow- bends like lead (Gray says it is brittle!), the differ- ers in when most other ent layers separating at the end. I cut a good-sized early April, plants switch, which was smgularly tough and flexible, are still dormant. Another point of interest 21

is its tendency to develop a single stem. This or imprecise (Esson 1949), I undertook a seed habit, which is unusual for a shrub, gives the germination project in 1979. At that time plant the appearance of a miniature tree and there were two Dirca plants at the Ar- makes it extremely useful in rock gardens boretum, both collected in New Hampshire and perennial beds. Despite leatherwood’s in 1961. In early June the mature fruits were preference for moist, shady sites in the wild, falling off. They were green at that point, it will tolerate full sun under cultivation. In- with a slight tinge of yellow. The fruit is a terestingly, when grown in the open the berry with a fleshy outer seed coat and a plant assumes a more compact habit of hard, black inner coat surrounding a single growth, and the foliage, which is light green large embryo. in the shade, takes on a distinct yellowish I followed my usual practice when pro- cast. cessing seeds preparatory to sowing them: I Because propagation data on leatherwood put them in a plastic bag and set them on a were either nonexistent (Schopmeyer 1974) headhouse bench until the fleshy part of the fruit softened enough so that it could be eas- ily washed off. This "fermentation" clean- The Atlantic leatherwood (Dirca palustns ~ pro- duces bright yellow flowers in early April. 22.

ing, as it is called, usually takes about one seedling was produced, but of the 77 un- week and works wonders with fleshy fruits cleaned ones planted outdoors, 47 seedlings like those of Malus, Comus, and Sorbus. germinated the following spring - a stagger- While this technique is not generally rec- ing 61 percent. Here I had brought to bear ommended in the seed germination litera- nearly 10 years of experience in botantical ture (Schopmeyer 1974), it has long been research, along with a barrage of hormones used successfully with many types of plants and climate-control devices, when success at the Arboretum. could be achieved only by doing nothing. After a week I removed the rotting Dirca Humility is what I learned from that exper- fruits from the bag and washed them clean iment. with water. I then subjected the seeds to var- In 1981 collected another 600 fruits from ious tests: some I sowed immediately in the Dirca to see if perhaps my experience in greenhouse, some I stratified (this involves 1980 had been a fluke. This time I set up a packing the seeds in a moist medium and surefire test. I divided the seeds into six lots: storing them in a refrigerator for three some I cleaned by hand, peeling the thin months), and some I treated with the plant green skin off with my fingernail; some I hormone, gibberellic acid ~GA3/. To my dis- cleaned by the usual fermentation method appointment, none of these treatments pro- in a plastic bag; and some I left uncleaned. I duced a single plant. then planted replicate lots outdoors under Trying again in 1980, I collected 1177 shade cloth and indoors in a greenhouse seeds and designed an experiment that I heated to a minimum of 45°F in the winter thought would cover all possible types of time. The results are shown below. seed-dormancy mechanisms. I put all the fruits in a plastic bag for fermentation clean- ing, except for 77 that I pulled out at the last Seedlmgs minute to use as a control. These I sowed in Treatment Location Produced a which was then outdoors to flat, planted 100 seeds uncleaned outside 32 simulate the conditions the seeds would 100 seeds uncleaned inside 25 have been subjected to had they been al- 100 seeds hand cleaned outside 54 lowed to fall from the plant. 100 seeds hand cleaned mside9 The remaining 1100 seeds were allowed to 100 seeds fermentation rot for several after which they were days, cleaned outside 1 cleaned and then subjected to every possible 100 seeds fermentation seed-germination test I could think of: strat- cleaned mside0 ification in the refrigerator, as well as in the greenhouse, gibberellic-acid soaks, and scar- ification with a knife. Finally, I carefully ex- In all cases, the seeds sown outdoors did cised over 400 embryos from their seed better than those treated in the same man- coats and gave them the same treatments. ner but sown indoors, and as a whole, the To my amazement, of the 1100 seeds so uncleaned seeds performed almost as well as carefully cleaned and treated, not a single the hand-cleaned seeds. Fermentation clean- 23

Jack, J. G. 1894. "The Earliest Flowering Shrubs." Gar- den and Forest, 7: 112-13. Nevlmg, L. I., Jr. 1962. "The Thymelaeaceae in the Southeastern Umted States."/ournal of the Ar- nold Arboretum, 43: 428-34. Schopmeyer, C. S., ed. 1974. Seeds of Woody Plants in the Umted States Agriculture Handbook No. 450. Washmgton, D.C.: United States Govern- ment Printing Office. Thoreau, Henry David. 1906. The Journal of Henry D. Thoreau. New York: Dover.

Flowers ot Atlantic leatherwood (Dirca palustris)(

ing was, of course, a disaster all around. More than anything else, this experiment demonstrates that some plants propagate themselves best when left to their own de- vices. With Dirca palustris, letting nature run its course is not only easy, but also very effective.

I

References Anderson, E. 1933. "Leatherwood." Bulletin of Popular Information, 4th ser., 1: 25-27. Esson, J. G 1949. "Leatherwood for Early Sprmg Bloom." ~ournal of the New York Botamc Gar- den, 50: 57-59.

When Is a Pine Not a B. June Hutchinson Pine?

Although it is commonly called the um- 1776. However, Thunberg’s mention of the brella pine, the luxuriant Sciadopitys ver- new evergreen was largely overlooked by ticillata actually is not a pine. In fact, it pos- botanists since he described it as a species of sesses no immediate plant relatives, and its the well-known genus Taxus. When ancestry is more remote than that of most German-born physician and botanist Philipp other conifers. The foliage is still another Franz von Siebold ( 179Cr18GG~ saw the tree, unusual aspect of this tree: it is comprised of he realized it was unique. The description of two types of leaves. The dark green needles Sciadopitys verticillata in his Flora Japonica that grow in distinctive whorls at intervals (1842) excited plant enthusiasts. Yet it was along its branches are one type, and the not until nearly 20 years later that umbrella small brown scales along the stems are an- pines were successfully propagated in En- other. gland by nurseryman John G. Veitch, who E. H. Wilson (1876-1930) called the um- brought seeds from Japan in 1861. The fol- brella pine "one of the most distinct of all lowing year the tree was grown for the first conifcrs" in appearance. Planted as a land- time in the United States at the Parsons scape specimen in the Northeast, it forms a Nursery in Flushing, New York. Although it dense pyramid and retains its lower is still not widely available in the United branches well into maturity, unlike many of States, a few fine nurseries in New England the conifers. Wilson wrote that he saw the sell the umbrella pine. Unfortunately, umbrella pine growing in the forests of Japan the long handling time in the nursery, due to (to which it is native) as a tall, narrow- slow growth, decrees a high price for these crowned tree up to 30 m in height, but in unusual plants. this country it is slow growing and reaches Dr. Sidney Waxman, of the University of 8 m at most after 50 years. Connecticut, has introduced several cul- This remarkable tree first became known tivars of the umbrella pine, which have been to Europeans when the Swedish botanist propagated from cuttings. His article in the Carl Peter Thunberg ( 1743-1828/ published International Plant Propagators’ Society a description of it in his Flora Japonica Proceedings (volume 28, p. 546-50) provides (1784), a work based on his observations dur- instruction on propagating by this method. ing a 15-month stay in Japan from 1775 to The Arnold Arboretum has successfully propagated umbrella pines from seed. The seeds required three months to germinate regardless of pretreatment. Arboretum trees Umbrella pine (Sciadopitys verticillata / produce cones in alternate years. 26 27

As described by both C. S. Sargent and formal country gardens, however. Umbrella E. H. Wilson, the native habitat and plant pines are perfectly hardy in the Boston area companions of the umbrella pine can guide and hold the dark green color of their thick, the use of the tree in the North American shiny needles through the coldest winters. landscape. Wilson wrote that it usually oc- Easy to grow and not susceptible to any seri- curs as a solitary tree or in small groves, ous diseases, they appreciate shelter from scattered through dense forests of pine, fir, strong winds and some soil moisture. Plant- Hinoki cypress, hemlock, maple, magnolia, ing sites should not be hot or dry but can be and katsura. Sargent reported finding it in shaded. association with native pines, particularly Japanese white pine (Pinus parviflora) and Facts about the umbrella pine (Sciadopitys Japanese red pine (P. densiflora/. In combina- verticillata)/ tion with the Japanese maple against an evergreen background, the umbrella pine is Landscape Height 7.5 to 9 meters an exciting study in leaf contrasts and form Spread 4 to 5 m for close-up viewing near a window or door- Texture Medium way. Another handsome grouping, which Growth Rate Slow has textual appeal, occurs naturally in Japan: Hardiness Zone5 a small grove of umbrella pines in combina- Family Pinaceae tion with hemlocks, accompanied by lower Native Range Japan Native Habitat dense of rhododendron and Scattered through plantings underplant- forests of mixed hard ings of Shortia. Mildly evocative of prehis- and soft woods. toric landscapes and matched in boldness of Introduced 1861 foliage and evolutionary age, Sciadopitys and magnolia are effective landscape com- panions. With a Magnolia x soulangeana ’Brozzoni’, for example, a small grove of three or more Sciadopitys is elegant, particu- larly if sited in front of other tall evergreens. These combinations can be used in several landscape applications, including border, edge, screening, and foundation plantings. The textural richness and symmetry of the umbrella pine are set off to good advantage in both formal gardens and the surroundings of contemporary houses. The form of this would not be suitable Japanese plant among B. June Hutchinson is a consultant to the Arnold naturalistic the groupings of plants in in- arboretum, a wnter, anda landscape designer. She is currently workmg on one of four volumes m the forth- corrnnggmdebook to theArnold Arboretum (supported m part by a grant from the National Endowment for Distinctive needles of the umbrella pine (Sci- the HumamuesJ, from which this article was ex- adopitys verticillata~( cerpted.

The River Birch Anne Carlsmith

Landscape designers are always looking for As the tree matures (40 years), the bark beautiful and adaptable low-maintenance thickens, darkens, and becomes deeply trees. Since the number of these trees cur- fissured, beginning at the bases of the rently available is low, however, the result trunks. The larger branches acquire a rough is often another planting of honey locusts or and broken surface, while the smaller ones maples. Yet alternatives do exist, and continue to exfoliate. The mature river birch worthy candidates are often overlooked by has an open habit and fine foliage texture; the nursery trade. One such is the river the leaves (4-8 cm long) are deep green and birch, Betula nigra L. very lustrous. Monoecius, Betula nigra In comparison to the white-trunked forms three-clustered staminate catkins in members of the birch family (Betulaceae), the fall, which become conspicuous when the river birch has long been ignored, though they elongate to 8 cm in spring. it is a graceful tree, with a warm red bark The river birch lives up to its name in its that exfoliates to pink-white. It is also willingness to thrive in damp soil or soil that adaptable to both flood and drought and is may be inundated for weeks in the spring. more disease-resistant and heat tolerant This characteristic makes it a special asset than any other birch. to the landscape designer: all authorities When young the river birch (also known as agree that it is one of the finest trees for the red birch) is delicate. If left unpruned, it damp ground. In addition, it has the advan- becomes multitrunked in its first or second tage of being drought-tolerant and therefore year, breaking at ground level into several has potential as a street tree. splayed stems. It is twiggy, with many hori- Betula nigra owes its adaptability to the zontal subbranches that recurve slightly. floodplain habitats of which it is characteris- The youngest twigs are lustrous red and tic. In the wild it grows along the banks of darken as they grow, eventually becoming streams, on the edges of ponds, and in marked by narrow lenticels. The bark then swamps, habitats that may be flooded in separates into thin flakes, which curl into spring and dry in summer. It attains its strips and cling to the wood indefinitely. largest size (27 m) in the damp bottomlands Bark color varies from tree to tree: the outer of the Gulf States and is most prevalent bark may be bright or subdued and the inner along the larger, slow-moving silt-laden bark may be nearly white. rivers. It grows thickly along the Mississippi and its tributaries, holding the muddy banks against erosion. Young river birch trees (Betula mgra) growing at the edge of Jamaica Pond in Boston, Massachu- The river birch is the only birch growing setts. Bruce Applebaum photo. in the South, and it has the widest distribu- 30

Leaves of the river birch (Betula mgra/. Bruce Applebaum photo. tion of all the North American birches. Its lists the river birch among the trees that natural range extends from New Hampshire have sprung up spontaneously in Central south to Florida and west to Texas and Min- Park and eventually replaced the installed nesota. it Donald Wyman has noted that plants (Arnold 1980). A low soil pH appears does well even in California (Wyman 1977a). to be the only definite requirement of the Native stands are sparse in zone 4, however, river birch. Chlorosis occurs at pH levels and trees there are both smaller in stature higher than 6.5 (Dirr 1983). and less long-lived (Steele and Hodgdon ’Heritage’, the only river birch cultivar, 1975). In New England the average stature at was selected for both a light bark color and a 30 years is 15-18 m, whereas in the South it prolonged period of exfoliation. Neither the can be as high as 27 m. species nor the cultivar is readily obtainable. Bronze birch borer, the most destructive of Weston Nurseries in Hopkinton, Massachu- birch pests, has virtually no effect on the setts, supply the species (and will supply the river birch, and leaf miner, another birch cultivar in spring 1984). Oliver Nurseries in pest, has very little. Atmospheric pollution Fairfield, Connecticut, and Mellinger’s in apparently is harmless also: Henry Arnold North Lima, Ohio, supply the cultivar. 31

difficult to transplant, except when balled and burlapped and moved in very early spring. (Most reputable nurseries dig them only at that time.) Again the river birch is the exception. Gary Hightshoe describes it as "easily transplanted [in] early spring or late autumn" (Hightshoe 1978). The tree is quick to throw out adventitious roots when flooded and generally shows the rooting vigor of all fast-growing trees. Birches in general are "bleeders," that is, they are slow to heal if pruned in spring, when sap flow is heaviest. Pruning in fall and early winter is preferable. Donald Wyman has observed a tendency in the river birch to form weak crotches, but a grove of mature trees in the Arboretum shows no evidence of it (Wyman 1977b). Planted from seed collected in 1877, these trees show the typical habit of the mature river birch in New England.

Peeling bark of a young river birch. Peter Del References Tredici photo. Arnold, Henry F. 1980. Trees m Urban Design. New York. Van Nostrand, Remhold. Dirr, Michael A. 1983. Manual of Woody Landscape Growing the River Birch Plants: Their Idenufication, Ornamental Charactenstics, Culture, Propagation and Uses Ready germination from seed is another 3rd edition. Champaign, Ilhnois. Stipes. Hightshoe, Gary. 1978. Native Trees for Urban and asset of the river but the seeds must be birch, Rural Amenca. Ames, Iowa: Iowa State Umver- collected early. This is the only Betula sity Research Foundation. species that ripens its seeds in spring or early Pirone, P. P. 1941. Mamtenance of Shade and Orna- mental Trees. New York: Oxford summer. Small and are University lightweight, they Press. dispersed by the wind and often carried long Steele, Fred L., and Albion R. Hodgdon. 1975. Trees and distances. Much of the seed falls near the Shrubs of Northern New England. 3rd edition New for the Pro- tree, however, so collection is not difficult. Concord, Hampshire: Society tection of New Hampshire Forests. that so Nurserymen report seedlings grow Wyman, Donald. 1977a. Trees for Amencan Gardens. quickly from seed that propagation by rooted New York- Macmillan. cuttings is unnecessary. A caliper of 8-10 cm . 1977b. Wyman’s Gardening Encyclopedia. Re- vised edition. New York: Macmillan. has been noted at 15 years. ’Heritage’, repro- duced by cuttings, grows equally quickly. Anne Carlsmith is a student in the Program in Land- Many nurseries list all the birches as scape Design at Radchffe College. COLLECTOR’S NOTEBOOK

Orchids for Everyone Richard E. Weaver, jr.

Orchids hold a fascination for plant growers that few other plant groups can match. For the gardener their beauty and rarity, and the challenge of cultivating many species, make orchids par- ticularly desirable subjects. Growing hardy native orchids has become a somewhat controver- sial subject, however, because most of those offered commer- cially have been collected in the wild, and wild populations of many species are becoming seri- ously depleted. Native orchids are also difficult to propagate. Only a few species, notably the large yellow lady’s-slipper (Cyp- ripedium calceolus var. pubes- cens), increase reliably in cultiva- tion. In addition, most native or- chids are to nearly impossible Bletilla stnata grow from seed with techniques presently available, and they have not yet responded to propa- them without having to worry several of the Japanese species of gation by tissue culture, like about endangering the species in Calanthe: C. nipponica, C. many of the tropical epiphytic the wild. In addition, these tricarinata, and C. discolor and orchids. species are more attractive than its-varieties. But those of us who want to many of our native orchids; they Because the propagation of grow orchids in our gardens now are easy to cultivate; and they are many hardy orchid species is have an alternative. Several Asi- hardy in most parts of the Umted difficult, gardeners are often re- atic species can easily be propa- States. I am referring particularly luctant to attempt it. But I urge gated both vegetatively and from to Bletilla striata, often sold as them to try. Bletilla and seed, so we can obtain and grow the "hardy Chinese orchid," and Calanthe are good choices with which to start, because success is backbulbs, but these have prefer to separate them by gently virtually assured. evolved as a safeguard, so that if twisting them apart. If a knife is Before attempting to propagate the leading tip of the rhizome is used, it is important to inspect these plants, it is important to damaged, or if the season’s aerial the backbulbs carefully for any understand some basic facts of shoot is destroyed (perhaps by a latent buds in order to avoid orchid growth. Most orchids late frost), one of these latent damaging them. Again, the lead- grow sympodially, that is, each buds will break dormancy and de- ing pseudobulb can be replanted shoot grows to maturity and then velop into a shoot. Thus the in the garden. The backbulbs can stops growing, whether it flowers damaged plant will still be able to be planted in a propagation or not. That shoot is then suc- grow. frame, but because the shoots ceeded by a similar one, which These latent buds also enable they produce are delicate and develops from an axillary bud us to propagate Bletilla and slow-growing I prefer to start borne on the rhizome. Old shoots Calanthe, as well as other or- them in a seed pan. I use a me- often live for several years, still chids, by vegetative means. If we dium consisting of 2 parts peat capable of food production and separate them, and the backbulb moss, 1 part vermiculite, and I storage but incapable of growth to which they are attached, from part perlite. The backbulbs or flower production. In terres- the leading shoot, each will de- should be situated so that their trial orchids the rhizome is usu- velop into a separate plant. The tops are just below the surface of ally underground. In many genera procedure is simple. For B. the medium. Place the pans m a the shoots themselves consist of striata dig up the plant in the shaded spot in a greenhouse or two distinct parts: an above- spring before the new shoots have outdoors, and keep the medium ground part, which includes the emerged, and carefully clean the moist. The tender shoots are very foliage and produces the flowers pseudobulbs so that each one is attractive to slugs, so it is best to and in temperate regions usually clearly distinguishable. Be extra apply a commercial slug bait as . dies back at the end of each sea- careful to avoid damaging the soon as the shoots appear. Leave . son ; and an enlarged underground leading buds in the process. Sever the plants in the pans under part, attached to the rhizome, the rhizome between each fluorescent lights or m filtered which serves as a food-storage or- pseudobulb with a sharp knife or sunlight until the following gan. The underground part varies pruning shears. The pseudobulb spring and then plant them m in structure and appearance from with well-developed buds may be their permanent place in the gar- genus to genus, but in Bletilla replanted in the garden, and the den. and Calanthe it is a pseudobulb shoots should develop and flower Other orchids with corms or similar to the aerial ones of normally. The backbulbs should underground pseudobulbs should epiphytic orchids (in Bletilla the be planted in a propagating frame, respond similarly to Bletilla and structure is often referred to as a covered with about 5 cm of soil Calanthe. Experimentation corm).( . and mulched lightly. They must should produce some interesting The pseudobulbs of Bletilla never be let dry out. The and valuable results. I hope that and Calanthe live for several backbulbs should produce small success with these will lead to years, and if an established plant shoots the first season, and the experimentation with other of either genus is dug up the resulting plants should flower the species and that eventually structures appear as a string of second season. My expenence methods will be found for prop- beads, attached by the rhizome. has been that backbulbs up to agating more of these wonderful The old pseudobulbs, referred to five years old should produce plants. as backbulbs, function primarily shoots if treated in the manner to store but associated with descnbed above. food, Richard E. Weaver, Jr, the former each are latent buds often not The procedure for Calanthe horticultural taxonomist at theAr- visible to the unaided eye. species is similar. The backbulbs nold Arboretum, now operates Normally such latent buds would of this genus are bome very WE-DUNursenes in Marion, North eventually decay along with the closely together, however, and I Carolina. BOOKS these plants can be found in the wild or in cultivation in New England and elsewhere when environmental conditions are similar to those of southern Ontario. Most, if not all, can be found well labeled and beautifully exhibited at the Garden in the Woods, Hemenway Road, Framingham, Massachu- setts. Flowers of the Wild: Ontario and the Great Books with photographs and graphics of Lakes Zile Zichmanis and Region by James this quality are rare. I commend the authors Toronto: Oxford Press. Hodgins. University on producing a book that organizes informa- 272 pp. tion on wildflowers in a convenient package, the of wild to the GARY L. KOLLER conveys beauty plants most uninformed reader, and pleases the Flowers of the Wild: Ontario and the Greatt most avid wildflower enthusiast. Lakes Region, is likely to become the first book I reach for when I am looking for a ref- erence guide to wildflowers. The text, which Plant Extinction: A Global Crisis by Harold covers 127 plants, is terse and includes the Koopowitz and Hilary Kaye. Washington: same categories of information on each Stone Wall Press. 239 pp. $16.95. plant. The categories are: habitat, longevity, flower and fruit characteristics, ecological MARK PLOTKIN status, and cultivation. The accompanying pictures are well composed and sharp in im- Many important international conserva- age, and the color reproduction is superb. I tion programs initially focused on prevent- have encountered few books on plants with ing the extinction of large mammals like the better photography. Botanically accurate tiger or the rhinoceros. This has proved to be line drawings, which are carefully stylized to a shrewd choice, as these animals appeal to accent characteristics that aid in identifying the general public and generate a great deal the plant, supplement the photographs. The of sympathy (and, therefore, dollars) to drawings also illustrate characteristics that finance programs for their protection. The may be unclear or not represented by even importance of these early efforts to elicit the best photograph. public support in industrialized nations for Each plant is represented on two pages, conservation programs in developing coun- with text occupying approximately one- tries should not be underestimated - that quarter to one-half page and the line drawing organizations were able to raise funds to a full page. save foreign wildlife species, which many of My only complaint is with the name of the donors would never see outside a zoo or a the book, which might lead one to think that television screen, was truly a noteworthy the plants treated will not be found outside achievement. Ontario and the Great Lakes Region. Most of Nevertheless, the success of these projects 35

solved only a small part of the problem. As Grenville Lucas, of the Royal Botamc Gar- dens at Kew, has stated, "the appeal of ani- mals like the panda and the muriqui is uni- versal, yet you cannot save the animals if you do not save the plants." A major problem then is "saleability" - how does one inter- est the general public in plant conservation? What is undoubtedly one of the best methods is presented in a new book by Harold Koopowitz and Hilary Kaye entitled Plant Extinction: A Global Crisis. By show- ing how crucial a role plants play in our daily lives (for example, the use of the rosy periwinkle [Catharanthus roseus] in treating cancer. the authors vividly illustrate that plant conservation is not an esoteric exercise but an urgent necessity. Plant Extinction contains intriguing in- formation on both the ancient, current, and future uses of plants and the causes of the rapidly accelerating pace of species extinc- tion. The authors have thoughtfully in- cluded data on the status of plant conserva- tion in biomes throughout the world, the politics of conservation, and the essential role that the hobbyist can play. Although a more in-depth citation of references would have made this book more useful to the sci- entific community, Plant Extinction is both enjoyable and informative and will un- doubtedly prove useful to the teacher, the hobbyist, and the general public. Arnoldia Landscaping Contest

Among the numerous mquiries that come to conditions. We would like information spe- the Arnold Arboretum by phone and letter, cifically on the following kinds of plantings: one of the most frequent is, "What can I plant annuals, ground covers, herbaceous perennials under my mature Norway maple (Acer and bulbs, deciduous and evergreen shrubs, platanoides) or European beech (Fagus syl- hedges, and vines and methods of support. vat1ca)?" These are trees that cast intense Information submitted will be presented in a shade and whose roots are shallow, fibrous, future issue ofArnoldia. All mformation mll and dense, factors that are unfavorable for un- be crechted to the contributor, and all’con- derplantings. tributions will be acknowledged. Participants We would like to hear about plantings that submitting the five most origmal photographs have not only survived but thrived beneath prior to October 1, 1984, will receive a plant of these and other shallow-rooted trees. Readers Styrax ~apomca ’Pink Chimes’ or another rare can help by sending descriptions, photographs, ornamental plant. Help us to assist others by or comments on plantings they know to have sharing your expertise. Contributions should been successful. Advice will also be welcome be addressed to: Gary L. Koller, managing hor- on special planting or maintenance techniques ticulturist, Arnold Arboretum, Jamaica Plain, that enhance the establishment and growth of MA 02130. the understory plants under these difficult