arnoUiaVolume 52 Number 3 Fall 1992

Arnoldia (ISBN 004-2633; USPS 866-100) is publishedquarterly, in winter, spring, summer, and fall, by TheArnold Arboretum of Harvard University. Second-classpostage paid at Boston, Massachusetts.

Subscriptions are $20.00 per calendar year domestic,$25.00 foreign, payable in advance. Single copies are$5.00. All remittances must be in U.S. dollars, bycheck drawn on a U.S. bank, or by internationalmoney order. Send orders, remittances, change-of-address notices, and all other subscription related com-munication to: Circulation Manager, Arnoldia, TheArnold Arboretum, 125 Arborway, Jamaica Plain, MA02130-3519. Telephone (617) 524-1718.

Postmaster: Send address changes to:Arnoldia, Circulation ManagerThe Arnold Arboretum125 ArborwayJamaica Plain, MA 02130-3519

Peter Del Tredici, EditorJudith Leet, Associate Editor

Amoldia is set in Trump Mediaeval typeface andprinted by the Office of the University Publisher,Harvard University.

Copyright © 1992, The President and Fellows ofHarvard College

Front cover: The curious flowers of Asimina tnloba,the pawpaw. Photo by Al Bussewitz.

Back cover: The fall foliage of Lmdera obtusilobagrowing at the Arnold Arboretum. This plant consis-tently produces spectacular clear-yellow autumn color.The red foliage of Sassafras albidum can be seen aboveand to the right. Photo by Peter Del Tredici.

Inside front cover: The fruit of Maclura pomifera, theOsage orange. From The Sylva of North Amenca by C.S. Sargent, drawn by C. E. Faxon.

Inside back cover: This gate, made of Japanese cypress(Chamaecyparis obtusa), was built in Kyoto andreassembled on site at Tenshm-en. Photo courtesy ofthe Museum of Fine Arts, Boston.

Page2 Tenshin-en

Julie Moir Messervy

14 Magnificent Maclura-Past and PresentJohn C. Pair

20 Our Native Pawpaw: The Next NewCommercial Fruit?M. Brett and Dorothy J. Callaway

30 Make Mine Mulch -

Peter Del Tredici

Pawpaw flower buds. Photo by Rdcz and Debreczy.

2

Tenshin-en: A Japanese Garden at Boston’s Museumof Fine Arts

Julie Moir Messervy

An urban haven for contemplation that embraces two cultures.

For many Westerners, the idea of owning aJapanese garden is an unreachable dream.Busy, stressed in their workaday world, theyimagine returning home to a serene paradiseof ancient stones perfectly set in a bed ofmoss, flanked by rippling waters of a koipond. Here, in this miniature world, theycan give voice to their inner thoughts, day-dreams, and spiritual longings; they canbecome their true selves in a garden ofbeauty.Few of us will have the space, find the

time, or have the money to create such asanctuary in our lives. How fortunate it is,then, that the Museum of Fine Arts, Boston,built just such a garden for all of us to expe-rience and enjoy. Sitting within its walls,closed off from busy Boston traffic andpassersby, one feels sheltered in an oasis,paradoxically surrounded by, yet removedfrom, present-day urban life and times.One sits in a curiously transcendent

world, feeling the stones as venerable soulsset with a modern freshness and vigor, rem-iniscent of rocky shorelines of New England,yet universal in the abstract power of theirdry composition. At first, the visitor feelsoverwhelmed by the energy of the place,nearly 200 rocks, set here and there, and

senses a mixture of design prowess and acci-dent. Equally impressive are the lushnessand quantity of the plantings: over 70

species-1750 specimens in all-adorn thelandscape, changing the feeling and form ofthe garden through the seasons. In earlyspring, the white-panicled flowers ofandromeda hang as tresses from the shinygreen of the shrub’s leaves. Mid-spring intoearly summer brings a continuous bloom ofazaleas in shades of white, fuchsia, rose,salmon, and pale pink, hummocking assmall hills at the feet of tall stones andlanterns. Early to midsummer brings thepurple, yellow, and white iris, standing inupright sheaths behind rocks. In fall, themaples, azaleas, and enkianthus turn bril-liant hues of red, yellow, and orange to markthe onset of colder weather, before the snowsdrape the garden in winter. One could attendthe garden every day and discover oneselfanew through the continuously changingappearance of plants amidst the unchangingstolidity of the stone elements.

A Merging of CulturesTenshin-en, the Garden of the Heart ofHeaven, is a 10,000-square-foot contempla-tive viewing garden located at the north side

The Japanese lantern located near the water basin at Tenshin-en. Photo courtesy of the Museum of FineArts, Boston.

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The crushed gravel "sea" at Tenshm-en. Raking gives the effect of ripples on the water’s surface. Photo cour-tesy of the Museum of Fine Arts, Boston.

of the West Wing of the Museum of FineArts, Boston. Completed in 1988, the gardenis named in honor of one of the museum’sfirst curators of Asiatic Art-Okakura

Kakuzo, also known as Okakura Tenshin.Tenshin-en is one of New England’s few

semipublic viewing gardens in the Japanesestyle. A true Japanese garden, according tocultural traditions, derives-and takes inspi-ration-from the landscape around it. In thisspirit the project team of landscape artistsflew over the New England region in a smallplane to gain a sense of its geography and aes-thetic qualities. The resulting garden is aninterpretation of two cultures, combining thedepth of meaning of Japanese garden symbol-

ism with a feeling of beauty and repose thatevokes the New England landscape. Rockycoastlines, deep forests, soft hillsides, andcraggy mountains are abstracted and recre-ated to remind viewers of the beauty anddiversity of this region. The intent, accordingto Professor Nakane, the garden’s designer,was to create in the garden "the essence ofmountains, the ocean and islands ... as Ihave seen them in the beautiful landscape ofNew England."Each rock, plant, and paving stone was

chosen from local materials and combinedwith artifacts selected from the Museum’scollection or brought from Japan. Togetherthese intermingle to create a contrast

5

Lookmg along the curved path towards the gate at Tenshin-en. Photo courtesy of the Museum of Fine Arts,Boston.

between natural materials and humanobjects and arrangements.

Origins of Tenshin-enThe Museum of Fine Arts, Boston, asked aninternationally known garden master fromKyoto, Professor Kinsaku Nakane, to designand construct a Japanese garden as an impor-tant addition to the museum’s world-renowned Asiatic collection. Funds for theproject were donated by the NipponTelevision Network Corporation, Mr. YosojiKobayashi, Chairman of the Board.As the garden master’s project coordinator,

my responsibility was to assemble a projectteam to carry out his conceptual designs.

The Halvorson Company, a Boston land-scape architecture firm, was chosen to pro-duce the technical documents and detailsnecessary to build a garden of another cul-ture in this country. Our mandate was tocombine an acute sensitivity to the nuancesof Japanese design with a full understandingof the legal and technical requirements ofbuilding projects in this country. Alsoincluded in the team were various subcon-tractors from this country and from Japan,each of whom brought specialized trainingand craftsmanship to different aspects of theproject. The landscape contractor was

Donald B. Curran, Incorporated of Ipswich,Massachusetts.

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The garden evolved through a style of col-laboration quite different from normalAmerican landscape architectural practice.The garden master’s concept and executionwere upheld by the efforts of every teammember in an atmosphere of unstintingcommitment to the creation of a work of art:the Museum’s curatorial staff guided the gar-den process and provided and conservedmany of its artifacts; the Italian masons setKyoto roof tiles on its walls; the Japanesecarpenters built a traditional gate in Kyoto,dismantled it, and reinstalled it on site withthe American carpenters’ help. All upheldthe master’s concept, in a collaboration ofthe highest order.On one of his trips to the site, Professor

Nakane was present to set the critical ele-ments that make up the structure of the gar-den. To watch him was to see a true masterat work. For six hot days in July, 1987,Professor Nakane established the positionsof the rocks in the garden. Attending to animage of power and beauty that existed onlyin his sketches and in his imagination, he setalmost two hundred stones.With the aid of a 100-foot hydraulic crane,

its highly attentive operator, and three land-scape crews, the shape of the garden began toemerge. One by one, the boulders, fillingeight tractor-trailer trucks, were bound andchained to the crane’s wire. Like the conduc-tor of a symphony orchestra, ProfessorNakane would indicate to one crew howdeep into the ground they should dig, and toanother which way the stone should face-and where its head, feet, front, and backshould be positioned. The crew placed thestones, some weighing as much as eighttons, in the ground and made minute adjust-ments under Professor Nakane’s watchfuleye. All this was done without a word spo-ken, as Professor Nakane speaks onlyJapanese.

Professor Nakane, in a calm and almostcasual way, would set one stone at thetakiguchi (waterfall), the next stone on thetsurujima (Crane Island), and the next in theforeground of the garden. He saw the finalresult in his mind’s eye and worked aroundthe whole garden to balance his compositionright from the start. As well as fitting intothe design as a whole, each stone groupinghad to be balanced in its own right-all ofwhich Professor Nakane accomplished withsplit-second decisions. When the composi-tion was complete, nothing needed to bealtered; the whole felt dynamic and yet bal-anced.

After he had set the stones, ProfessorNakane returned to Japan while the wallsand new sidewalks were installed. On hisnext trip to Boston he set fifty-two trees onthe day he arrived, but unexpectedlyreturned to Japan the following day, calledback because of a death at the Osaka

University of Fine Arts, which he heads. Atthat point, his son and chief assistant ShiroNakane took over and set the remainingplantings, ornaments, and stepping stones,and supervised the erection of the Japanesegate.

Professor Nakane returned one more timefor the opening of the garden on October 24,1988. At that time, he declined to speak butchose instead to paint a sign for the garden insumie-Japanese ink. Inscribed is ten, shin,and en (with Chinese characters) in his ownbeautiful calligraphic hand. Since then,Tenshin-en has been opened to the publicfrom spring through fall and is visited bythousands of people every year.

Design Features of Tenshin-enTenshin-en is designed as a viewing gardenin the karesansui style, harkening back toZen temple gardens of the fifteenth centuryin Japan. Kare means "dry," san, "moun-

The plan of Tenshin-en at the Museum of Fme Arts, Boston. Reproduced courtesy of the Museum of Fme Arts,Boston.

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tain," and sui, "water"; thus it is a "drymountain water" garden, or a dry landscapegarden. Water is suggested by the rakedgravel "sea," which unites all the landformsof the garden-the mountains, islands, androcky shoreline formed by mounded earthand rocks.

Tenshin-en relates to its surroundings bya technique called shakkei, that is, by bor-rowing and echoing the distant landscapeand bringing it into the garden walls. Curvedshorelines and bridges within the gardenecho the lines of the Fenway landscape thatabuts the museum on its north side,designed by America’s premier garden mas-ter, Frederick Law Olmsted. Olmsted

designed parks and green spaces during thelate 1800s, creating Boston’s "Emerald

Necklace," the park system that links openspace from Franklin Park to the BostonCommons as one nearly continuous sweepof green. Although conceived and designedon a scale far vaster than Tenshin-en’s minia-ture landscape, Olmsted understood theneed to evoke a harmonious understandingof nature, as he wrote in 1879: "We want a

ground to which people may easily go aftertheir day’s work is done, and where theymay stroll for an hour, seeing, hearing, andfeeling nothing of the bustle and jar of thestreets, where they shall, in effect, find thecity put far away from them."

A Deeper Reading of the GardenVisitors who understand the garden’s sym-bolism will probably have a richer experi-ence of it. The dry "waterfall" (takiguchi) tothe back and left of the garden represents theBuddhist concept of shumisen or Mt.

Sumeru, a mythic mountain thought to sup-port the heavens above and the world below,and around which the universe was believedto be centered. The two "islands" in the leftand right center of the garden are two of the"Mystic Isles of the Immortals," Taoistmythical islands said to bring immortalityand prosperity to those who incorporated

them in their gardens. To the left is kame-jima, the Tortoise Island; to the right is tsu-rujima, the Crane Island. Looking carefully,one can see the head, feet, tail, and flippersof the tortoise, and the head, wings, and tailof the crane.

According to Professor Nakane, "Themountains and islands symbolize the nat-ural beauty of this region [New England],and, at the same time, mean enduring pros-perity and happiness for the Museum visi-tors." If one studies the garden’s designfeatures, the rocky coastline to the rightrecalls the Maine Coast, and the two largerocks on Crane Island suggest Mt. Fuji (onthe right) and one of New England’s bestknown peaks, Mt. Monadnock (on the left).Looking carefully, one can see a profile muchlike that of New Hampshire’s "Old Man inthe Mountain" on the floating islandbetween the Crane Island and the rockycoast. The stepping stone path area is anabstraction of deep forests, and the mossyhillside behind the Crane Island recalls the

softly forested landscape of New England.

The Stones

In the Japanese garden, the stones are thebackbone and provide the overall structure.Rocks from Topsfield, Boxford, and Rockport,Massachusetts, total about 390 tons. Each isplaced according to ancient rules and tradi-tions dating back to the Middle Ages ofJapanese history. A dark granite verticalstone and base, carved in Japan, is located tothe left of the waterfall, and says Ten-shin-en in Chinese characters, a gift of the gar-den’s donor, Yosoji Kobayashi.

The Wall and Japanese GateThe wall is a modern interpretation of aJapanese mud-and-wattle wall, seen in tem-ple compounds and surrounding traditionalgardens all over Japan. This wall, varying inheight from five to seven feet, was con-structed of poured concrete mixed with alight colorant, which was then sandblasted

9

One of the curved budges which link the "islands" to the "mainland. Photo courtesy of the Museum of FineArts, Boston.

to roughen the texture. The base band is ofgranite from Deer Isle, Maine, resemblingthe facade of the museum’s West Wing.From the outside, one can see only a nar-

row round cap of tiles of a simple design tomeld with the spare lines of the West Wing.From the inside, one sees the full slant of theroof that protects a typical wall from the ele-ments. These silver tiles are made of claybaked four times rather than the usual two,in order to accommodate Boston’s moresevere climate. An old Kyoto firm,Yokoyama Seiga Kojo, specializing in shrineand temple roof tiles supplied the 1500pieces that make up the roof, includinground roof tiles, stacked tiles, beam tiles,

and eaves tiles. A special Museum of FineArts emblem tile, onigawara, featuring themuseum’s seal, was also made up andgrouted to the end wall at the EducationEntrance.The imposing Japanese gate is called

kabuki-mon, meaning "hanging gate" (anddoes not refer to the famous Japanese the-ater.) A traditional gate for a mountain castleor large palace in Japan, it was chosen as aJapanese-style horizontal counterpoint toarchitect I. M. Pei’s large concrete beam atthe entrance to the West Wing. The gate isbuilt of Japanese cypress, a wood with excel-lent natural preservatives. Special design fea-tures of the gate are the 13-inch-wide post

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Perennials in Tenshin-en

Six hundred perennials adorn the garden.Ferns of many varieties are used withhostas and liriope to soften the appear-ance of the rocks. Leatherleaf ferns aswell as lady, hart’s tongue, Japanesepainted, Christmas, and maidenhair ferns,abound in the garden. Hostas include’Gold Standard’, ’Green Fountain’,’Francee’, ’Blue Cadet’, ’Nakiana’, and’Flavo Circinalis’, with five giant hostasfeatured outside the walls (’Halcyon’,’Christmas Tree’, ’Nigrescens’, ’FrancesWilliams’, and ’Blue Angel’). Other peren-nials include bloodroot (Sanguinariacanadensis), trillium (Tnllium grandiflo-

rum), goatsbeard (Aruncus canadensis),lady’s mantle (Alchemilla pubescens), iris[Iris ensata, sibirica, and cristata), gerani-ums (Geranium endressi ’Johnson’s Blue’,G. sanguineum), astilbes (Astilbe chinen-sis ’Pumila’, ’William Buchanan’), bleed-ing heart (Dicentra eximia ’Zestful’), wildginger (Asarum europaeum), liriopes, andsedges (Liriope spicata, Carex comca’Variegata’). One can also spot pachysan-dra (P. terminalis ’Cutleaf’) planted as aspecimen near the water basin and step-ping stone path. The groundcover moss isPolystrichum commune, known as hair-cap moss.

and beams (kasugi, or "umbrella wood"curved beams above the two small doors),the ornamental nail covers, and ironwork.The gate was constructed in Japan by

Suzuki Komuten, carpenters who specializein building traditional Japanese structures.After being erected once for approval inJapan, it was disassembled and rebuilt inBoston. The wrought-iron fittings, hinges,and nail covers, also fabricated in Japan, areof traditional design.

The Water Basin

The water basin, or chozubachi, enables avisitor to ritually purify his or her body andmind as preparation for contemplating thegarden and for receiving inspiration andrenewal from its spiritual meaning. Similarstone basins were used in tea gardens as ves-sels for ritual cleansing before taking tea.This chozubachi is in the fusen style, fumeaning "to proclaim" and sen meaning"spring of water."The stones around the water basin are

arranged in the original Koho-an style. The

large stepping stone upon which one kneelsto partake of the water is called a maeishi, or"front stone"; the stone to its right is theyuokeishi, or "hot water container stone,"on which such a container would be placedin winter so that guests could add hot waterto the basin to warm their hands. The stoneto the left is the teshokuishi, or "hand can-dle stone," on which a guest might place aportable candlestick when using the gardenat night.

The Stone Lanterns

Stone lanterns were originally used as votivelights placed in front of Buddhist templebuildings. In later years they played a moreornamental role and were designed specifi-cally for garden use-to light the path to a teahouse or to light certain areas of a garden.Near the water basin is a small Japaneselantern of the Edo period (1603-1867), origi-nally located in the Japanese Court of themuseum’s Asiatic Collection. It has a tall

mushroom-shaped "hat" and is placed so thatit can cast light over the water basin at night.

11

In the northeast corner of the garden is akasuga-style lantern, a reproduction of onefrom the Kawageta Temple, the original con-sidered a "very important cultural property"by the Japanese Government. Dating from1311, the lantern is a very good example oflate Kamakura-period (1185-1333) lanterns. Itshows the then prevailing concern withpower and beauty in its attacking lion andpeacock carvings. Single petals of lotus arecarved at the base, a Buddhist symbol of thesoul’s ascent from mud to the glory of flow-ering.

Just inside the gate is another kasuga-stylelantern, a reproduction of the main lanternat the Joruri-ji Temple near Kyoto, carvedabout 1366. The shape of this lantern fol-lows the composition of the Kawagetalantern but it is narrower overall: the lotuspetals are taller, the window is smaller, andthe curve to the roof is steeper.A large Korean lantern in a fourteenth-

century style, originally located in the court-yard of the museum, is situated in thesoutheast corner of the garden. Outside thegarden wall is a Meiji-period lantern, datingfrom about 1880, featuring ornamentalfriezes of mountains and deer.

The Paths

Japanese garden paths are based on the prin-ciple of shin-gyo-so. The path outside thegate is of the shin, or "formal" style, thestepping stones are of the so, or informalstyle, and the curved nobedan path is of thegyo style (somewhere between informal andformal in style). The cut stones on thecurved path are surrounded by black-washedMexican river stones set in mortar. Thispath brings one to the cut stone terrace onwhich are three shogi benches of traditionaldesign. The informal stepping stones pathscalled tobiishi, take the visitor to the Koreanlantern, the water basin, or are used as analternate route back to the Japanese gate.There are also three bridges that link the

"islands" with the "mainland" and form a

path for the viewer to take a visual ratherthan an actual journey. These bridges, calledsoribashi, or "curved bridges," are as long as17 feet and weigh as much as 1.5 tons.

The PlantingsOver seventy species of plants give color andtexture to the garden. Cherries, Japanesemaples, and pines are all signature plants ofa Japanese garden and serve as symbols ofthe changing seasons. Tenshin-en is com-posed of a mixture of Japanese and Americanspecies; such plants as Japanese Cryptomeriacombine with American holly to create anew horticultural interpretation of an

ancient art form.

Trees: Japanese maples, called kaede, or"frog’s hand" or momiji, are mainstays of aJapanese garden. Used to create a feeling ofmountain scenery at the edge of a forest,they link open land to forested land.Broadleaf evergreen trees are generally nothardy in the Northeast, so American hollies,Ilex opaca, were used in place of some of theevergreen oaks that, in Japan, act as tall ever-green screens to give the sense of a deep for-est. Needle-leaf trees, including compactselections of the Canadian hemlock (Tsugacanadensis) and Cryptomeria japonica’Yoshino’, are used to create a lush back-ground to the waterfall and mountain pathareas. Cryptomeria is part of the indigenousvegetation in Japan and are planted exten-sively in holy areas such as shrine precincts.Red pines (Pinus densiflora) and tanyoshopines (Pinus densiflora ’Umbraculifera’) areused to highlight the islands.Deciduous trees used in the garden

include Stewartia pseudocamellia, moun-tain ash (Sorbus decora), star magnolia(Magnolia stellata), and of course cherries:the weeping cherry by the gate (Prunus sub-hirtella ’Pendula’), October cherries (Prunussubhlrtella ’Autumnalis’) and Sargent cher-ries {Prunus sargentii). The Japanese admirecherries as symbols of a life well-lived-they

12

Stone lanterns are used to light paths and highlight special areas of the garden’s design. Photo taken m 1988 andreproduced courtesy of the Museum of Fine Arts, Boston.

bloom suddenly and abundantly, but aregone nearly overnight, suggesting a good wayto face death as well.

Shrubs: The 1100 shrubs in the garden pro-vides its finished and colorful look. About500 azaleas of many varieties provide colorover two months in the spring. Earlybloomers include the Korean azalea (Rho-dodendron poukhanensis) and varieties of R.mucronulatum. The popular ’Delaware

Valley White’ azaleas and early reds

(’Hinocrimson’ and ’Hinodegiri’) mix with

midseason bloomers of various colors: salm-on (’Guy Yerkes’), silver-pink (’Kaempo’),white with pink throat (’Geisha’), white(’Girard’s Pleasant White’, ’Polar Bear’), rose-red (’Vyking’), and the beautiful ’PurpleGem’. Late-blooming varieties include theNorth Tisbury hybrids (’Wintergreen’,’Yuka’, and ’Marilee’). Azaleas are pruned inthe karikomi, or cloud-form shape, to sug-gest the billowing forms of hills and tosoften the base of the stones.Other shrubs used extensively are moun-

tain laurels [Kalmia latifolia), andromeda

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(Pieris japonica, P. floribunda), enkianthus(Enkianthus campanulatus), kerria (Kerriajaponica), daphne (Daphne burkwoodii’Carol Mackie’), forsythia (Forsythia inter-media ’Arnold Dwarf’), barberries (Berberisthunbergii, B. mentorensis), junipers [Ju-niperus procumbens ’Nana’, J. chinensis

’Sargenti’), euonymus (Euonymus alatus),holly (Ilex pendunculosa), and dwarf spiraea(Spiraea japonica ’Little Princess’).

Maintenance

Contrary to popular opinion, a Japanese gar-den is not a low-maintenance landscape.One day a week throughout the garden’sopen season, a maintenance crew comes totend the garden. Every week the crew prunescertain trees and shrubs, weeds the moss,and rakes the gravel. Other gardening choresoccur at specific intervals during the year:moss is trimmed for propagation, perennialsare cut back or divided, fertilizers or horti-cultural sprays are applied, hemlock barkmulch is spread; azaleas are deadheaded andalso pruned at least twice a year to maintaintheir shape and size.Viewers are always curious about how the

garden is raked. Crushed granite gravel fromMt. Airy, North Carolina, represents the"sea" of the garden’s landscape. A heavy six-tine rake is used to give the effect of rippleson the water’s surface. Starting from the nearright-hand corner of the garden, the crew

rakes in lines parallel with the West Wingwall. When the raker reaches an obstacle,such as a stone or island, he stands on it andrakes around it in a circle, continuing the pat-tern under the bridges and around alldetached stones. Finally, the raker follows theedge of the garden’s "sea" around the perime-ter until meeting the gate. The abstract linesof "water" are most apparent during rainy orcloudy days, or when the textures are empha-sized by a thin veneer of snow.

Tenshin-en is frequented by viewers com-ing to learn about another culture’s gardenart, to enjoy the verdant atmosphere, or toseek a moment’s peace. In the Garden of theHeart of Heaven, visitors will feel the truthof the words of Okakura Tenshin who once

said, "One may be in the midst of a city, andyet feel as if one were far away from the dustand din of civilization."

Tenshin-en is open to Museum of Fine Artsvisitors from April to November, Tuesdaysthrough Sundays, from 10 a.m. to 4 p.m.

The designer of the Arnold Arboretum’s Linda J.Davison Memorial Path and the project coordinator ofTenshm-en during its construction, Julie Moir Messervyis a landscape designer living in Wellesley. She is authorof Contemplative Gardens (Howell Press, 1990) and iscurrently finishing a new book, The Inward Garden, tobe published by Little Brown and Co. m September1993.

Magnificent Maclura-Past and Present

John C. Pair

New cultivars of the Osage orange have stimulated interest in thisdistinctive native tree.

The Osage orange, Maclura pomifera, has along and interesting history of use by bothNative Americans and early pioneers (Sand,1991 Its wood was once in demand for mak-ing hubs and wheel rims for horse-drawnvehicles, mine timbers, posts, and other useswhere resistance to rotting was important.Its decay resistance is due to the chemical2, 3, 4, 5-tetrahydroxystilbene, located in thewood and toxic to many fungi (Smith andPerino, 1981). ).

Perhaps the species is best known as a"living fence" because of its stout thorns onzigzagging branches, ease of propagation,rapid growth, and tolerance to heat, drought,and wind. Osage orange was first cultivatedin the South in the early 1800s. The plantreached Jacksonville, Illinois, by 1830,brought north by Professor Jonathan Turner,a biology teacher from Illinois College, andpromoted through the efforts of John A.Wright, editor of The Prairie Farmer. By 1847Turner was convinced that Osage orange wasthe best fencing material available, describ-ing it as "horse high, bull strong, and pigtight"; it functioned as a fence long beforethe invention of barbed wire, which did notcome into wide use until 1875 (Dick, 1975).Maclura pomifera, a member of the mul-

berry family (Moraceae), grows best in therich bottomlands along the Red Riverbetween Texas and Oklahoma. It also occursnaturally across southern Missouri, Ar-

kansas, and parts of Louisiana (Smith andPerino, 1981 The species is often referred toas hedge apple, or just "hedge," from itscommon use as hedges and windbreaks inthe plains states. Dunbar and Hunter sug-gested the idea of cultivating Osage orangeas a hedge to President Thomas Jeffersonupon return from their expedition to the RedRiver in 1806 (Morton, 1967).The common name of the plant comes

from its globular, characteristic fruit, aboutthe size of a large orange, borne on femaletrees of this dioecious species (Figure 1). TheFrench found the Osage Indians makingtheir bows from its wood and called it boisd’arc (meaning wood-of-the-bow). Suchbows were so highly regarded by Indiantribes to the north that they were consideredworth a pony and a blanket in trade.Recently the tree has been advocated as anurban tree for difficult planting sites (Powell,1979).

The Champion TreeThe champion Osage orange tree in theUnited States was reported in 1939 to belocated in Charlotte County, Virginia; itmeasured 15.5 meters (50.9 feet) high, witha circumference of 7.5 meters (24.5 feet) anda spread of 28.2 meters (92.5 feet)(Collingwood, 1939). Recent correspon-dence has indicated that this same tree,although somewhat in decline, is still on

IS .1;

Figure 1 ’I~pical /rujt and thorns of Maclura pomifera, both undesirable when the tree is planted for land-scape use.

the front lawn of the restored home ofPatrick Henry, near Red Hill, Virginia, andis now nearly 18 meters (59 feet) high with acrown spread of 30.5 meters (100 feet) and atrunk diameter of 2.7 meters (9 feet) (Figure2). The Henry family reports that the fam-ily physician present when Patrick Henrydied on June 6, 1799, became so upset at notbeing able to save the legendary patriot thathe went outdoors and "threw himself under-neath a large tree, weeping bitterly" (Daily,1983). The Osage orange is thought to be the"large tree" mentioned, a living landmark ofanother era.The largest Osage orange in Kansas grows

in Labette County and measures 18 meters(59 feet) tall with a 21.3-meter (70 feet)

crown spread and a 4.8-meter (15.8 feet) cir-cumference. Although doubts have beenexpressed about the hardiness of this south-ern species, it has survived as far north asthe Platte River in central Nebraska (Dick,1975). Large specimens occur across south-eastern Iowa and central Illinois and Ohio,and it has also been planted along the WestCoast. Internationally, it has been reportedgrowing in the British Isles, France,Germany, Italy, the Netherlands, Portugal,Romania, Russia, Switzerland, and Aus-tralia (Spaulding, 1956).After the Osage orange became widely

planted as fencing around small farms, itquickly invaded the prairies, occurring assmall, pure stands or with mixed hardwoods;

16

Figure 2. The champion Osage orange tree at the home of Patrick Henry in Charlotte County, Virginia. Thetree is nearly sixty feet tall, with a nine-foot trunk diameter.

it moved into the eastern states, becomingnaturalized in abandoned fields. The specieshas no natural pests.

Thornless and Fruitless Selections

Although Rehder (1967) reported a thornlessvariety of the Osage orange, Maclura

pomifera var. inermis, such specimens areuncommon, and some horticulturists sug-gest that they are merely mature specimensof trees that were typically thorny whenthey were more juvenile. However, isolatedthornless trees have been identified, and afew are creeping into the commercial trade.

Kansas State University has been identifyingand evaluating thornless selections for overtwenty-five years (Pair and Keen, 1980). Thefirst introduction made in the mid-1970swas ’Pawhuska’, named after an OsageIndian chief. The most recent release is’Wichita’ (Figure 3), a thornless male selec-tion found growing near Wichita, Kansas(Pair, 1991). /.Other selections propagated from large

specimens located in Oklahoma, Kansas, -and Iowa continue to be evaluated. Quitepromising is one called ’Whiteshield’, foundgrowing along Whiteshield Creek, and

17

named after a Cheyenne Indian chief. Thetree has glossy, cordate-shaped leaves (Figure4) and was discovered by John Flick nearHammond, Oklahoma. Another large malespecimen without thorns, found by AlFerguson growing in an old nursery nearDenmark, Iowa, is being propagated for com-parison with nine other clones at theHorticulture Research Center in Wichita,Kansas.

PropagationOsage orange is easily propagated in a varietyof ways. Seedlings, traditionally used forwindbreaks or as understock for improvedselections, are grown from stratified seedremoved from the large, leathery fruit col-lected in the fall. Seed slip easily from thepulp if allowed to ferment in water for sev-eral days. Stratification for 30 to 45 days at4 degrees Centigrade (40° F) is usually suffi-cient to break dormancy so seed can beplanted in the greenhouse in January orFebruary. If sown outdoors in the fall, ger-mination will occur in April or May the fol-lowing spring. Seedlings large enough forT-budding can be produced by mid-August.Budding can be done in August using vig-

orous, current season’s growth directly fromany superior plant. Such buds will remaindormant until forced out the following Aprilor May. Alternatively, dormant scionwoodcan be collected during winter and stored forJune budding once bark slips on the under-stock.Bench grafting is also easily accomplished

using either a whip and tongue or cleft graftin midwinter. Grafts should be allowed tocallus six weeks at near 12 degreesCentigrade (55° F) before potting up or lin-ing out in the spring. The rootstock shouldbe the same size as the scions used, or larger.Wrapping with grafting tape or masking tapesecures the union until callusing occurs.

Cuttings, both softwood and hardwood,are commonly used to propagate thornlessand fruitless selections vegetatively. Tender

Figure 3 A ten-year-old specimen of Maclurapomifera ’Wichita’, a thornless, male cultivar.

shoots, fifteen centimeters (6 inches) long,taken in May or early June and placed underintermittent mist, will root in five to sixweeks. Rooting hormones greatly increasethe percentage and the numbers of roots pro-duced. Concentrations of indolebutyric acid(IBA) ranging from 2,500 to 5,000 parts permillion are usually adequate. The commer-cial talc formulation Hormodm® No. 2(3,000 ppm) works well. Softwood cuttingsready for potting in August need winter pro-tection before lining out the followingspring.Hardwood cuttings can also be propagated

easily with wood collected from January toMarch. With this method, plants of suffi-cient size can be produced for lining out thesame season. Pair and Khatamian (1984)

18

Figure 4. A fruitless and thornless selection of Maclura with glossy, cordate-shaped leaves.

found basal stem portions rooted better thanterminal sections when taken off maturetrees. Wood collected in winter should becut into six- to eight-inch cuttings, dipped in5,000 to 10,000 ppm IBA, and placed overbottom heat near 21 degrees Centigrade(70°F) in a cool greenhouse (13 to 18 degreesCentigrade [55-65° F]). The rooting mediumcan be either perlite or a mixture of perliteand peat in a two-thirds to one-third ratio,and should be kept moist, but not too wet.Bottom heat allows callusing and rooting tooccur before leaves emerge from the cuttings(Figure 5).Cuttings taken as late as March 1 often

root in three weeks and can be potted up ineight weeks-until of sufficient size for lin-ing out in early summer. Since there is a

strong tendency for multiple stems to occurin this species, cuttings can be grown for oneseason without pruning or training. If theplant is cut back to a single bud near the basethe following spring (as in propagation bybudding), a strong central leader can be pro-duced to form a better, single-stemmed tree.Osage orange has seldom been used as a

common residential tree. Its wide-spreadingroot system requires ample space, but itsrustic beauty-particularly when the glossygreen leaves turn yellow in autumn-canprovide shade and ornamental value to parksand landscapes and at the same time sym-bolize the American frontier.As improved selections become available

and the demand for stress-tolerant, pest-resistant trees increases, greater use may be

19

Figure 5. Rooted hardwood cuttings of Maclura afterfour weeks of bottom heat and a treatment of 5,000ppm IBA

made of male Maclura cultivars. From thewindswept prairie to the inner city, this treemay fill the need for those difficult plantingsites where few other species can survive.

References

Collingwood, G. H. 1939. Osage-orange. AmencanForests 45: 508-510

Daily, P. 1983. Osage orange at Red Hill: tale of a tree.Virginia Forests 39(3): 22-23.

Dick, E. 1975. Fences. In Conquenng the Great

American Desert Lincoln: Nebraska StateHistorical Society, pp. 72-81.

Morton, C. V 1967 Freeman and Custis account of theRed River expedition of 1806, an overlookedpublication of botanical interest. Journal ofthe Arnold Arboretum 48 431-459.

Pair, J. C 1991. Maclura pomifera’Wichita’. AmencanNurseryman 174 (8): 146.

- - and R. A. Keen, 1980. Propagation of thorn-less-fruitless selections of Osage orange.Proceedmgs of the International Plant

Propagators Society 30: 348-353.

- - andH.Khatamian 1984 Rooting of thornlessOsage orange by hardwood cuttings as

affected by IBA concentrations and stem por-tion. The Plant Propagator 30(1) : 6-7.

Powell, T. 1979 Taming the Osage orange. The AvantGardener 2(13): 1.

Rehder, A. 1967. Manual of Cultivated Trees andShrubs New York: Macmillan Co

Sand, S. 1991. A tree history: the Osage orange.American Horticulturist 70(10): 37-39.

Smith, J. L., and J. V. Permo. 1981. Osage orange(Maclura pomifera): history and economicuses. Economic Botany 35: 24-41.

Spaulding, P. 1956. Diseases of North American ForestTrees Planted Abroad USDA Handbook 100.

John Pair is a Research Horticulturist for Kansas StateUniversity at the Horticulture Research Center inWichita, Kansas.

20

Our Native Pawpaw: The Next New CommercialFruit?

M. Brett and Dorothy J. Callaway

Asimina triloba can add a distinctive look to your garden and a tropical tasteto your table.

If someone told you about a tree bearingfruits that are delicious and exotic in flavor,custard-like in texture, and larger than anyother native to the United States, you wouldprobably assume that this fruit was alreadypopular in the marketplace. If you learnedthat this same tree possessed large, highlyornamental, dark-green leaves that turned abrilliant gold in the autumn, you would sus-pect that you had probably seen it in manyyards. You would, however, be mistaken inboth cases. The tree in question is the nativepawpaw, Asimina triloba. But why is a fruitwith such potential not already a commer-cial crop? How can the pawpaw benefit fromwhat we know of the commercial develop-ment of other fruit crops?

Species and TaxonomyThe genus Asimina has the northernmostrange within the primarily tropical family,the Annonaceae. It includes eight speciesand one named hybrid, all native to temper-ate North America. Each of the eight speciesand one hybrid of Asimina are brieflydescribed below and in Table 1. Either decid-uous shrubs or small trees, Asimina speciesproduce flowers in the spring, often beforethe alternately arranged leaves have

emerged. The flowers are protogynous, thatis, the stigmas in a given flower maturebefore the stamens. Flower petals are

arranged in two whorls of three (or morerarely, four). The fruits are cylindrical,many-seeded berries, usually ranging inlength from 2 to 9 centimeters (1-4 inches),although some specimens of A. triloba bearfruit as long as 15 centimeters (6 inches).Table 1 provides a comparative list ofAsimina species, their synonyms, floweringand fruiting times, and other plant charac-teristics.The most recent taxonomic study of the

genus Asimina was carried out by Kral(1960). His treatment is widely followed,except for one species that Kral calls A. spe-ciosa, but that is more commonly referred toin the literature as A. incana or A. incarna.We believe A. incarna to be the legitimatename of this species. Detailed distributionmaps for species in the genus Asimina areprovided by Callaway (1990).

Species in the Genus AsiminaAsimina incarna, a small shrub with obo-vate leaves and white flowers, is native tosandy ridges and old fields from centralFlorida north to southeastern Georgia.

Asimina tnloba, from The Sylva of North America by C. S. Sargent. Drawn by C. E. Faxon.

22

23

The attractive foliage of Asimina tnloba. Photo byAl Bussewitz.

A. longifolia, a small shrub with narrowleaves and white flowers, is native to flat-woods and sand ridges from northeasternFlorida to southeastern Alabama.

A. obovata, a shrub or small tree with obo-vate leaves and white flowers, is native todry sand ridges, coastal dunes, and ham-mocks throughout most of peninsularFlorida.

A. parviflora, a large shrub or small tree,with oblong leaves and maroon flowers, isnative to rich woods, lime sinks, and alluvialsoil of coastal hammocks from Florida tosoutheastern Virginia, west to Tennesseeand eastern Texas.

A. pygmaea, a dwarf shrub with obovate oroblanceolate leaves and maroon flowers, isnative to flatwoods and savannahs from cen-tral Florida to southeastern Georgia.

A. reticulata, a shrub with oblong or ellip-tic leaves and white flowers, is native tomost of the Florida peninsula.

A. tetramera, a shrub with oblanceolate or

elliptic leaves and maroon flowers, is nativeto coastal sand dunes in the area of Martinand Palm Beach counties, Florida.

A. x nashii, the only named Asimina hybrid,is a naturally occurring cross between A.mcarna and A. longifolia. Described by Kralas occurring where the ranges of the two par-ent species overlap, it is a shrub with whiteflowers; its leaves are intermediate in sizebetween the two parents. Although otherAsimina hybrids were discussed by Kral(1960), only A. x nashii was named.

Asimina triloba, by far the most widespreadand northernmost species of Asimina,deserves special attention. A shrub or smalltree with maroon flowers, it is native tomost of the eastern half of the United Statesfrom Florida to Ontario, west to Nebraskaand Texas (see range map). The fruit of A.triloba, unlike that of most of the otherspecies, is palatable, large, and deserving ofcommercial exploitation.

Horticulture of Asimina triloba

Because of transplanting difficulties, paw-paws are best started as seedlings in deepcontainers and grown to a height of 0.6 to 0.9meters (2-3 feet) before they are transplantedto the field. Seedlings should be protectedfrom direct sunlight for the first year ofgrowth because of their sensitivity to ultra-violet light. In their second and subsequentyears, however, plants should be placed infull sun for best fruit production (Willsonand Schemske, 1980). The limited cultural

24

Growing m the understory of a forest m SouthCarolma, the alternate arrangement of the foliage ofthe pawpaw is both obvious and distinctive. Photoby Peter Del Tredici.

information available for pawpaw is summa-rized by Callaway (1990, 1993).

Diseases and Pests

Diseases of Asimina include flyspeck(Zygophiala jamaicensis) and a leaf spotcaused by a complex of pathogens (Myco-centrospora asiminae, Rhopalocomdiumasiminae, and Phyllosticta asiminae) (Nasuand Kunoh, 1987; Peterson, 1991). None ofthese diseases cause significant damage tothe fruit. Insect pests include two leaf feed-ers, Eurytides marcellus and Omphaloceramunroei (Damman, 1986), and one pedun-cle borer, Talponia plummeriana (Allard,1955). T plummeriana may cause serious

flower loss in some years. A number of ver-tebrates (foxes, opossums, and squirrels) areknown to eat pawpaw fruit.

PropagationPawpaw seed should not be allowed to dryout before planting. Small quantities areplaced in polyethylene bags containing dampsphagnum moss. Cold stratification at 2 to4 degrees Centigrade (35-39°F) for 60 to 100days is recommended (USDA, 1948). Rate ofgermination is improved by bottom heat (27to 30 degrees C [80-86°F]) and shading(Callaway, unpublished; Evert and Payne,1991; Peterson, 1991). The most reliablemethod of vegetative propagation is chip-budding. Root cuttings have also been suc-cessful (USDA, 1948). Tissue culture andsoftwood propagation methods have notbeen satisfactorily developed.

Varieties

Compilations of information on past andpresent varieties of Asimina triloba have

appeared in reports by Callaway (1990, 1993)and Peterson (1991). Much of the informa-tion available on varieties is subjective andof questionable value. Many so-called vari-eties are trees that were named by theirowner and reported in the literature of vari-ous fruit-grower societies, but never propa-gated for distribution. However, untilproperly conducted variety trials are carriedout, these are the best sources of informa-tion available. Of the sixty-eight varietieslisted by Callaway (1993), commercial sup-pliers are known for nineteen. However,only ’Sunflower’ is listed by more than twonurseries. (It is listed by six.) Eight are listedby two nurseries and 10 by only one. ’Davis’,’Overleese’, and ’Sunflower’ are probably themost widely grown varieties. ’Overleese’ and’Sunflower’ are generally considered amongthe best selections currently available.Selected from the wild around 1950 inRushville, Indiana, ’Overleese’ bears fruitweighing approximately 350 grams (12.3

25

The range of Asimma tnloba, the pawpaw. From Atlas of United States Trees, Vol. 4, Minor Eastern Hardwoods.1978. USDA Misc. Publ. 1342.

ounces) and ripens about the first week ofOctober in Michigan. ’Sunflower’ fruits,somewhat smaller, weigh approximately 250grams (8.8 ounces) and ripen in Michigan atabout the same time as ’Overleese’.’Sunflower’ originated in Chanute, Kansas.

Utilization and ProspectsCurrently, pawpaws are primarily consumedas fresh fruit. They may also be processedinto ice creams, juices, and other products asare their Annona relatives. In addition tofood uses, scientists at Purdue Universityhave isolated compounds from vegetativeparts of the pawpaw that exhibit highlyeffective pesticidal and anti-tumor proper-

ties (Alkofahi et al., 1989; Rupprecht et al.,1986; Rupprecht et al., 1990). Pawpaw alsodevelops into a very handsome ornamentalplant. In the open, trees assume a pyramidalform. Throughout the summer they areadorned with large, drooping, dark-greenleaves which turn brilliant golden in the fall.Despite the fact that pawpaw is native to

the United States, its commercialization isapparently more advanced in other coun-tries, such as Japan and Italy. We are aware ofonly one commercial planting in the UnitedStates and their plants are still too small tobear fruit. Fortunately, this lack of interestseems to be changing. Pawpaw plants haverecently been selling briskly in the nursery

26

The fmit of Asimina tnloba hangmg from a tree at the Arnold Arboretum. Photo by Al Bussemtz.

trade, particularly grafted varieties, and noneof the nurseries selling pawpaw varietieshave been able to meet the demand for

plants within the last two years. Althoughadequate assessment of market demand fornew crops is quite difficult, recent trendsindicate that the prospects for successfulcommercialization of this fruit appear to be

improving.

Difficulties in New Crop IntroductionAsimina triloba was widely used by NativeAmericans before European settlement.

Although early settlers also used pawpaw,they also brought fruit-such as apples,peaches, and pears-with them from Europe.

In the Old World, superior varieties of thesefruit had been selected over several centuriesand propagated widely by grafting. Therefore,these improved fruits were more widelygrown than unimproved native fruits.Although exceptional specimens of paw-

paws can be found in the wild, the proportionof superior plants, as with any wild fruit(apples, peaches, and pears included), issmall. Historically, many years are requiredfor exceptional specimens to become widelydistributed. Early efforts at collecting excep-tional specimens were made by the Amer-ican Genetic Association (Anonymous, 1916,1917) and by a few individuals, most notablyDr. G. A. Zimmerman (1938, 1940, 1941) of

27

A selection of Asimma triloba producmg exceptionally large fruits Photo by Brett Callaway.

Harrisburg, Pennsylvania. Unfortunately,many specimens identified during thisperiod were lost during World War II. Inrecent years renewed efforts by a few indi-viduals have led to a resurgence of popularinterest in pawpaws.The improvement of crops through breed-

ing is particularly slow for tree crops becauseof the long intervals between generations.Often a breeder is only able to evaluate fiveor six generations in an entire career. Whenone considers that a corn breeder can evalu-ate three generations a year, the comparativedifficulty of developing new varieties of fruitcrops from trees or shrubs becomes obvious.However, there have been successes.

Domestication of the blueberry (Vacciniumspp.) has taken place entirely in the twenti-eth century (Galleta, 1975). The first com-mercial plantings were established in Floridain the late 1800s (Lyrene and Sherman, 1979)and breeding work began in the early 1900s.’Tifblue’, probably the most widely grownrabbiteye type of blueberry (V. ashei) isderived from parents collected from the wild(Austin, 1985). Kiwi (Actinidia chinensis) isanother example of a recently developedfruit enjoying commercial success. There-fore, Asimina germplasm collections madein recent years by Peterson (1986) andCallaway (1991), and a number of superiorvarieties collected from the wild (listed by

28

Callaway, 1993), provide the foundation forpawpaw breeding work to begin.

Lessons from Other CropsImportant lessons are to be learned from theearly efforts at commercialization of blue-berries. Between 1921 and 1925, a boom inthe Florida blueberry market took place.Hundreds of thousands of plants were dugfrom the wild and planted in commercialfields. The extreme variation in fruit qual-ity from these wild plants (as would be thecase for any wild fruit) led to a decline indemand for the Florida fruit and caused the

industry to shift to more northern parts ofthe U.S. where superior varieties were clon-ally propagated and grown (Lyrene andSherman, 1979). The great demand for paw-paws in recent years has led to a shortage inplants of superior varieties. Customers areplaced on waiting lists, sometimes for years.Under these conditions, as in the boom yearsof the Florida blueberry industry, the temp-tation to plant seedlings of variable qualityis great. However, this practice is short-sighted and can potentially destroy a

nascent industry.

References

Alkofahi, A., J. K. Rupprecht, J. E Anderson, J. L.

McLaughlin, K L. Mikolajczak, and B. A.Scott. 1989. Search for new pesticides fromhigher plants, pp. 25-43. In J. T. Arnason, B. J.R. Philogene, and P. Morand (eds.). AmericanChemical Society Symposmm Senes 2, No.387.

Allard, H. A. 1955. The native pawpaw. AtlanticNaturalist 10(4): 197-203.

Anonymous. 1916. Where are the best papaws? Journalof Heredity 7 291-296.

Anonymous. 1917. The best papaws Journal ofHeredity 8(1)’21-33.

Austin, M. E. 1985. Rabbiteye blueberry breeding.Unpublished mimeo.

Callaway, M. B. 1990. The pawpaw (Asimma tnloba).Kentucky State University Publication CRS-HORT-901T.

Callaway, M. B. 1991. Germplasm collection using pub-lic contests-the Asimina tnloba example.Hortscience 26: 722.

Callaway, M. B. 1993. Pawpaw (Asimma tnloba), a"tropical" fruit for temperate climates. In J.Janick and J Simon (eds.). New CropsExploration, Research, CommercializationNew York: John Wiley.

Damman, A. J. 1986. Facultative interactions betweentwo lepidopteran herbivores of Asimina

Oecologia 78: 214-219.

Evert, D. R., and J. A. Payne. 1991. Germination ofAsimina tnloba and A. parviflora.Hortscience 26: 777.

Galleta, G. J. 1975. Bluebernes and cranberries. In J.Janick and J. N Moore (eds.). Advances inFrmt Breedmg, pp. 154-196. West Lafayette,Indiana: Purdue University Press

Kral, T. 1960. A revision of Asimma and

Deenngothamnus (Annonaceae). Bnttoma12(4):233-278.

Lyrene, P. M., and W. B. Sherman. 1979. The rabbiteyeblueberry industry m Florida-1887 to 1930-with notes on the current status of abandoned

plantations. Economic Botany 33:237-243.

Nasu, H., and H. Kunoh. 1987. Scanning electronmicroscopy of flyspeck of apple, pear,Japanese persimmon, plum, Chinese qumce,and pawpaw. Plant Disease 71:361-364.

Peterson, R. N. 1986. Research on the pawpaw (As1mmatnloba) at the University of Maryland.Northern Nut Growers Association Annual

Report 77: 73-78.

Peterson, R. N. 1991. Pawpaw {Asimma). In J. N. Mooreand J. R. Ballington (eds.). Genetic Resourcesof Temperate Frmt and Nut Crops, pp. 567-600. International Society for HorticulturalScience, Wageningen, The Netherlands.

Rupprecht, J. K., C.-J. Chang, J. M. Cassady, and J. L.McLaughlm. 1986. Asimicm, a new cytotoxicand pesticidal acetogenm from the pawpaw,

29

Asimma tnloba (Annonaceae). Heterocycles24:1197-1201.

Rupprecht, J. K., Y -H Hui, and L. McLaughlin 1990.Annonaceous acetogemns a review. Journalof Natural Products 53:237-278.

U. S. Department of Agriculture. 1948. Asimma tnloba(L.) Dunal, pawpaw. Woody-Plant SeedManual. U.S. Dept. of Agriculture Misc Pub.654.

Willson, M. F., and D. W. Schemske. 1980 Pollinatorlimitation, fruit production, and floral displayin pawpaw [Asimma tnloba). Bulletm of theTorrey Botamcal Club 107:401-408

Zimmerman, G. A. 1938. The papaw. Northern Nut

Growers Association Annual Report 29 :99-102.

Zimmerman, G.A. 1940. Further report on the papaw.Northern Nut Growers Association Annual

Report 31 133-134.Zimmerman, G. A. 1941. Hybrids of the American

papaw. Journal of Heredity 32(3):83-91.

M Brett Callaway is Tropical Germplasm Manager forPioneer Hi-Bred International and Adjunct AssistantProfessor of Horticulture at the University of Kentucky.Dorothy Callaway is a freelance horticultural writerand author of The World of Magnolias, soon to be pub-lished by Timber Press, Portland, Oregon.

Make Mine Mulch

Peter Del Tredici

Using mulch in the garden not only reduces maintenance, but also contributesto the overall health of the plants.

The use of organic mulches in landscape sit-uations mimics the natural processes thatoccur in deciduous forests where a "blanket"of leaves is deposited on the forest floorevery fall. Leaves not only act to insulate thesoil during the winter but also are the mech-anism by which carbon and mineral nutri-ents are recycled through the ecosystem (seeThe Organic Matter "Recycle" flow chart).In the list below I have summarized the prin-cipal benefits of mulch from the gardeningperspective, along with some cautions aboutits use.

Benefits of Organic Mulch1. Conserves WaterThe most immediate effect of mulch is toreduce water evaporation from the soil sur-face. By protecting the soil surface from thedrying effects of the sun and wind, mulchpromotes water conservation.

2. Inhibits Weed GrowthA one- to two-inch layer of mulch will sup-press the growth of many weeds, especiallyannuals, thereby reducing the amount ofweeding time required.

3. Improves Soil StructureOrganic mulch acts as a source of carbon forsoil decomposers, which turn it into humus.Humus benefits the soil by improving its

tilth and water-holding capacity, and byincreasing soil aeration. Mulch is the mostcost-effective way of improving the com-pacted condition of many urban soils.

4. Adds Mineral NutrientsAs organic mulching material decays, min-eral nutrients are absorbed by symbioticmycorrhizal fungi, which pass them on toplants in "exchange" for carbon (see flowchart). These nutrients, including phospho-rus in particular, are essential for the healthygrowth of plants.

5. Moderates Soil TemperatureMulch helps protect the root zone of plantsfrom fluctuations in temperature. In sum-mer, the soil under mulch is both cooler andmore uniform in temperature than bareground. In winter, mulch can act as animportant soil insulator, particularly inyears when there is no protective snowcover. By reducing soil temperature fluctua-tions, mulch also helps to prevent smallplants from being heaved out of the groundduring the winter.

6. Reduces Soil ErosionSoil covered with mulch is better able toabsorb rainfall than bare soil, thereby reduc-ing soil erosion, particularly on steep slopes.

(continued on page 32)

31

The Organic Matter "Recycle"

32

Problems With Mulch

1. Can Cause Temporary NitrogenDeficiencyBecause of the high carbon-to-nitrogen con-tent ratio of most organic mulches, theyshould always be top-dressed with a lightsprinkling of an all-purpose garden fertilizer(such as 5-10-5) in the spring. Supplementalnitrogen not only speeds up the decomposi-tion process, but also serves to minimize thetemporary translocation of nitrogen from thesoil to the mulch layer by fungal decom-posers.

2. Can Provide Habitat for HerbivorousAnimalsMulch provides excellent habitat for volesand other rodents, as well as for slugs andsnails, making control measures more diffi-cult than they would be if the soil were bare.

3. Can Be Applied Too ThicklyOn young plantings, too much mulch can bedetrimental by inhibiting water penetrationand air flow. In general, two inches of mulch

should be the maximum depth with woodyplants. With herbaceous perennials, too

much mulch can lead to rot problems, par-ticularly during a wet growing season.

Conclusion

From the gardening perspective, mulchaccounts for the improved growth of plantsin two ways: first, it improves conditions forthe growth and development of beneficialsoil microorganisms by providing them withboth carbon and mineral nutrients; and sec-ond, it promotes increased root growth byincreasing the water-holding capacity of soiland improving its tilth. The use of organicmulches in the garden promotes the sameharmonious interactions between plantroots and soil microorganisms that occurnaturally in our native forests.

Peter Del Tredici has recently been appointed to theposition of Assistant Director for Living Collections atthe Arnold Arboretum. He has served as Editor ofArnoldia for four years.

NEWSfrom the Arnold Arboretum

A Mission Reaffirmed

Robert E. Cook, Director

The historical mission of theArnold Arboretum has beencaptured in the story of E. H. "Chi-nese" Wilson, vividly recounted bySteve Spongberg in his wonderfulbook about botanical exploration, AReunion of Trees. In a disastrous colli-sion with a rockslide on a mountain

trail in central China, Wilson suf-

fered a severely broken leg that re-

quired three operations. Despitethis, he managed to return to Bos-ton with 1,285 packets of seeds andmore than 50,000 pressed and driedherbarium specimens. As a result

there grows today, on the south side

of Bussey Hill, accession number

7272, a magnificent specimen of theSand Pear (Pyrus pynfoha) that firstcame to this country in seed lot 395

collected by Wilson near Ichang,China.

In 1988 the President and

Fellows of Harvard College reaf-firmed the historical mission of

the Arboretum:

2022 To maintain and curate a docu-

mented collection of woody plantshardy in the Boston climate;

2022 To study such plants throughmaintenance of a library and her-barium for research and teaching;

2022 To give instruction, including

E. H. Wilson began bis first Arboretum-sponsored expedition with the purchase of ahouseboat for travels on the Yangtze River. Pictured here with its crew in 1907, the craftwas christened ’The Harvard. "

public education, about the biol-

ogy of trees.

The modern execution of this

mission, and its roots in the heritageof Wilson, is embodied in the workof Dr. Jun Wen, a Putnam ResearchFellow at the Arboretum For the

past two months she has been travel-

ing m her native China to collect

seeds, prepare herbarium specimens,and sample living tissue, which isfrozen in liquid nitrogen for later

analysis These collections will

complement comparable collectionsshe gathered at the Arboretum last

spring.

Dr Wen is examining an oldscientific problem: Why do so manyspecies of plants native to easternNorth America also have closely re-lated sister species growing in east-

ern Asia? Is this an evolutionary co-

incidence, or were these species once

part of widely distributed ancestors?With her collections of living tissuefrom the Arnold Arboretum and

from distant locations in China, Dr.

Wen will be using the techniques ofmolecular biology to isolate DNAfrom her specimens and compare the

genes of these apparently closely re-lated species. By combining these

(continued on page 2)

(continued from page 1)

results with traditional morphologi-cal and paleobotamcal evidencefound in the herbarium and librarycollections of the Arboretum, she

will be able to reconstruct the his-

tory of divergences that createdthese groups and come to a much

more fundamental understanding oftheir evolutionary relationships.

Dr. Wen also collected and

shipped seeds of a number of Asian

species to the Arboretum, some of

which have never been grown in this

country before. Of special interestare propagules of Aralia henryi andHalesia matgregom. They have been

logged into our computer databasefor future germination and plantingon the grounds There, beside the

original collections of Wilson, theywill someday provide critical mate-rial for some other research project

unseen by us today.As we lay plans for the next

quarter century at the Arboretum,we are continually returning to thefundamental importance of our col-

lections, including the historicOlmsted landscape in which theyare set. We shall maintain our tradi-

tional commitment to their excep-tional care and curation. At the

same time we are actively seekingnew opportunities for the use ofthese collections that transcend our

historical mission As was the case

with E. H. Wilson in the early yearsof this century, challenging oppor-tunities, often in distant, unexploredregions of the world, will make theArboretum an international leader

in botanical research and education.

The Arnold Arboretum Associates conducted their Tenth A nnual Rare Plant Auction on

September 20. Shown here are some of the volunteers whose hard work made the eventrun so smoothly. They, and many others, deserve congratulations and a big thanks for atradttton of excellence that has brought people and plants together in support of the ArnoldArboretum.

A Federal Grantfor LEAP

Dtane Sy Person

The Arboretum has beenawarded a $37,000 grant fromthe Dwight D. Eisenhower Mathand Science Education Program forthe teacher training component ofthe 1993 LEAP (Learning About

Plants) Teacher Project. Allocated

through the Massachusetts HigherEducation Coordinating Council,this fundmg will support an ex-

panded Arboretum commitment to

improving the quality of scienceeducation in the Boston elementaryschools. In collaboration with the

Boston Public School Science De-

partment, 25 teachers from twelve

schools will be selected to partici-

pate in the 1993 summer workshop.These teachers will take part in an

intensive study of botany, horticul-ture, and ecology that emphasizesthe basic plant science concepts andhands-on learning strategies that

underlie the LEAP curriculum. Par-

ticipants will mentor others in theirhome schools, ultimately introduc-

ing the LEAP curriculum and re-lated Arboretum resources to a total

of 75 Boston teachers and their

students.

First ArboretumDeland Award

S tuart Davies, a graduate studentat Harvard University, has re-ceived the Arnold Arboretum’s

Deland Award in support of his

studies of the comparative systemat-ics and ecology of tropical rainforesttrees.

The Deland Award was re-

cently established from a bequest ofF. Stanton Deland, Jr., to supportresearch on the biology of woodyplants. Mr. Davies, the first recipi-ent of the award, will combine on-

going field studies in Malaysia withresearch in the Harvard UniversityHerbaria in Cambridge.

3

Completion of the ;

Lilac Renovation =

Peter Del Trediac

BV/ ltn the planting of eighty* new accessions, the restora-

tion of the lilac area, which was

started over five years ago, has been

completed. Most notable among the

new additions are forty large speci-mens that were moved in from the

Case Estates with the generous assis-

tance of labor and equipment byOllie Capizzi of Capizzi and Com-

pany of Acton, Massachusetts.

Working with Tony Capizziand a mechanical tree spade, JimNickerson and Bruce Munch of the

Arboretum grounds crew dug the

forty plants over a three-day periodand moved them into Jamaica Plain

on a flatbed truck All were plantedin their permanent locations within

a week of being dug, no small task

given that many of the plants

weighed close to a thousand pounds.A new bed containing seven

cultivars recently introduced by thelate Father John Fiala of Medina,

Ohio, has also been established. All

of the introductions selected for the

display have spectacular flowers and

appear to be fairly mildew resistant.To round out the renovation,

thirty lilac accessions from the Dana

Greenhouse nursery were plantedthroughout the lilac area In all, overone hundred plants were added to

the collection, all within the spaceof six weeks, a remarkable feat con-

sidering that the Arboretum was

packing up and moving during thesame time period. A hearty con-

gratulations to everyone whoworked so hard.

The Arnold Arboretum has been awarded the City of Boston’1: 1992 Auardfor Best Kept

Neighbor in the Open Space category. The people responsible for keeping the Arboretum are,

from left to right, top rou : Bruit Munch, Pat Wdlougbby, Bob Farmgliett/.JimNickenon, Mike Gormley, Luis Colon, Julie Coop, Karl Homes; bottom rou: Dave

Moran, Jim Papargins. Mark Walkama. Dennis Hams. Maurice Sheehan. and Don

Gatnck Kenny Clarke is missing from the picture.

With this issue Peter Del Tredici

leaves the editorship of Arnoldta andturns his full attention to the LivingCollections He was appointed Assis-tant Director for the Living Collec-tions this past summer. Peter has

been associated with Harvard Uni-

versity for 20 years, first at Harvard

Forest in Petersham as a researcher,

then as Assistant Plant Propagator ofthe Arnold Arboretum He was

awarded the PhD in biology by Bos-ton University in 1991 for study inthe evolution and natural history of

Gingko btloba. Recently Peter has

been studying patterns of regenerationin a variety of woody plants, includingKalmia. Castama. and Sequoia

Karen Madsen has been appointedEditor of Arnoldia. She brings longexperience m editing both books and

periodicals and is an instructor inthe Graduate Program in LandscapeDesign and History of the Radcliffe

College Seminars A past contributorto Arnoldia. Karen has participatedin many of the courses and tours of

the Arboretum She will welcome

your opinions and ideas as she beginswork on the next issue

4

Botany Courses atthe Arboretum

Marcia Mitchell

bot’a’ny n. The division of biologythat treats of plants with reference totheir structure, functions, classifica-tion, etc.

Many people first encounter

the Arnold Arboretum’s Liv-

ing Collections on a casual stroll

through the grounds. On subse-

quent visits, as they become familiar

with the geography of the Arbor-etum’s 265 acres, they come to seethe diversity of plant structures andthe variations in form and texture.

Some visitors remain quietly inter-ested observers, content to pursue

private thoughts or conversations as

they walk the Arboretum’s roads.

For other visitors, however, the

initial contact with the Arboretum’s

vast collection of woody plants is the

beginning of a lifelong exploration.It is for these visitors that the Arbo-

retum has long offered adult educa-tion courses in botany, as well as

many courses in horticulture.

Through these courses, most

designed to cover the planned mate-rial in six course sessions or fewer,adult students can gain a greater ap-

preciation of the links between spe-cies of woody plants, and an under-

standing of the systems of classifica-tion by which plants are described.Some of the Arboretum’s botanycourses are designed solely as class-room learning: many of these take

place during the cold wintermonths. Others are planned around

study of specimen trees and shrubson the Arboretum’s grounds, and

these are invariably some of themost popular courses offered in theArboretum’s adult education pro-

gram. For those who find that their

curiosity is whetted by the displayaround them, the Arboretum’s

botany courses will introduce thecareful observer to new worlds of

plant appreciation and enjoyment.

A Selection of Botany Offerings

BOT 131 Flora of New England:A Comprehensive SurveyThis course provides an opportunityfor the experienced plant enthusiastto gain a comprehensive knowledgeof our native New England flora.

Participants will learn the region’s

major vascular plant families, in-

cluding characteristic species andhabitats.

BOT 100 Introduction to Botany

Designed as an introduction to

botany for students new to the disci-

pline, this course also serves as a re-fresher for those who feel the need to

brush up on old skills. Among the

topics to be explored are plant cellsand tissues, cell division, plantanatomy and morphology, plant di-

versity, evolution, and ecology.

BOT 228 The Conifers

The conifers, or cone-bearing plants,are a major component of the New

England landscape. We will discussthe natural history of conifers andlearn how to recognize the native

genera and species. Students will see

what traits distinguish one conifer

species from another, how conifers

reproduce, and why conifers are such

special plants.

Please call the Education Department,524-1 718, to request a course catalogueor to register for Arnold Arboretum

Lilacs, recently moved tn from the Case Estates, had to be planted with a backhoe.