777 HORTSCIENCE, VOL. 31(5), SEPTEMBER 1996 The Pawpaw [Asimina triloba (L.) Dunal]: A New Fruit Crop for Kentucky and the United States Desmond R. Layne 1 129 Atwood Research Facility, Kentucky State University, Frankfort, KY 40601 midspring (Fig. 1). In the mid-Atlantic states and Ohio Valley, pawpaws usually flower immediately after the peak of dogwood (Cornus florida L.) flowering. Blossoms occur singly on previous- year’s wood and may reach up to 5 cm in diameter. Individual flowers are pendant on nodding, sturdy, pubescent peduncles up to 4 cm long (Kral, 1960). Mature flowers have an outer and inner layer of three, maroon-colored, three-lobed petals (Fig. 1). Inner petals are smaller and more fleshy, with a nectary band at the base. Flowers have a globular androecium and a gynoecium composed of three to seven carpels (Kral, 1960). The actual upper limit for carpel count may be nine or higher, based on the finding of nine-fruited clusters (R.N. Peterson, The PawPaw Foundation, personal observation). Flowers are strongly protogynous and self-incompatible, and require cross- pollination (Wilson and Schemske, 1980), although some trees may be self-compatible. Pollination may be by flies (Wilson and Schemske, 1980) and beetles (Kral, 1960), which is consistent with the presenta- tion appearance of the flower: dark, meat-colored petals and a fetid aroma. Fruit set in the wild is usually low and may be pollinator- or resource-limited (Wilson and Schemske, 1980), but under cultivation, tremendous fruit loads have been observed (R.N. Peterson, personal communication). Fruit are oblong-cylindric berries that are typically 3 to 15 cm long, 3 to 10 cm wide, and weigh 200 to 400 g. They may be borne singly or in clusters that resemble the “hands” of a banana plant (Musa spp.) (Figs. 1 and 2). This highly aromatic, climacteric fruit has a ripe flavor that resembles a creamy mixture of banana (Musa ×paradisiaca L.), mango (Mangifera indica L.), and pineapple [Ananas comosus (L.) Merr.] (McGrath and Karahadian, 1994). When ripe, skin ranges from green to brownish-black, and the flesh ranges from creamy white through bright yellow to shades of orange (Fig. 2). The skin should not be eaten. Shelf life of a tree-ripened fruit stored at room temperature is 2 to 3 days. With refrigeration, fruit can be held up to 3 weeks while maintaining good eating quality. Within the fruit, there are two rows of large, brown, bean-shaped, laterally compressed seeds that may be up to 3 cm long (Fig. 2). In the wild, the primary fruit consumers and seed dispersers are raccoons [Procyon lotor (L.) Elliot], red foxes [Vulpes fulvus (Desmarest) Merriam], and opossums (Didelphis virginiana Kerr) (among others) who eat fruit that have fallen to the ground (Peterson, 1991). Seeds contain alkaloids in the endosperm that are emetic (Vines, 1960). If chewed, seed poisons may impair mammalian digestion, but if swallowed whole, seeds may pass through the digestive tract intact. PROPAGATION AND CULTIVATION Seedling production As soon as flesh is soft, collect fruit for seed. Avoid excessive fermentation of the fruit, as prolonged exposure to the fermentation products may injure and kill the seed. Seeds are easily extracted following maceration of the fruit in water and floating off of pulp [U.S. Dept. of Agriculture (USDA), 1948]. Sterilize seed by shaking them with a 10% to 20% sodium hypochlorite solution for 1 to 2 min followed by several rinses of distilled water. This step aids in reducing fungal and bacterial contamination during storage. Do not allow seeds to dry out. Once cleaned, store them refrigerated in self-closing polyethylene bags with slightly moist sphagnum (or peat) moss. Label the bags, using indelible ink, as to the seed source, extraction date, and other pertinent information for future reference. Seeds have a dormant, immature embryo and require stratification (USDA, 1948). Storage under refrigeration (5C) for 100 days is recommended to overcome embryo dormancy (USDA, 1948). Provided that desiccation and microbial contamination do not occur, seeds may be stored for several Received for publication 30 Sept. 1995. Accepted for publication 23 Oct. 1995. I thank R. Neal Peterson, R. Jones, and E.A. Sugden for some of the photo- graphs used in the manuscript; and R.J. Barney, R.N. Peterson, and U.L. Yadava for suggestions regarding the manuscript. I thank R.L. Geneve, H. Huang, K. Kaul, R.N. Peterson, and D.E. Riemenschneider for scientific input toward the research projects described herein. The technical assistance of M.G. Kwantes, S.C. Jones, E.B. Reed, Jr., C.L.H. Finneseth (Univ. of Kentucky graduate student), and S. Johnson, S. Larkin-McMillon, O. Mitchell, and D. Prince (all Kentucky State Univ. undergraduate students), and L. Jones (a high school research apprentice) is gratefully acknowledged. Use of trade names and individual sources does not imply endorsement of the products named nor criticism of similar ones not named by Kentucky State Univ. In some cases, more than one commercial source is available for the products mentioned. The preparation of this paper was supported by U.S. Dept. of Agriculture/Coopera- tive State Research Service Agreement no. KYX-10-92-19P. 1 Principal Investigator of Horticulture and Curator, U.S. Dept. of Agriculture National Clonal Germplasm Repository for Asimina spp., Kentucky State Univ., and Adjunct Assistant Professor of Horticulture, Dept. of Horticulture and Landscape Architecture, Univ. of Kentucky, Lexington, KY 40546. ORIGIN AND BOTANY The pawpaw is the largest tree fruit native to the United States (Darrow, 1975). This fruit, known commonly as the “poor man’s banana,” may reach up to 1 kg in weight. Pawpaws grow wild in the rich, mesic hardwood forests of 25 states in the eastern United States, ranging from northern Florida to southern Ontario (Canada) and as far west as eastern Nebraska (Kral, 1960). Pawpaws flourish in the deep, rich, fertile soils of river-bottom lands where they grow as understory trees or thicket-shrubs (Sargent, 1890). Pawpaw is the only temperate member of the Annonaceae family (Bailey, 1960), which includes several delicious tropical fruits, such as the custard apple (Annona reticulata L.), cherimoya (A. cherimoya Mill.), sweetsop or sugar apple (A. squamosa L.), atemoya (A. squamosa x A. cherimola), soursop (A. muricata L.), and biriba (Rollinia mucosa Baill.). In addition to the tropical annonas, there are eight other members of the Asimina genus that are native to the extreme southeastern states of Florida and Georgia. These include A. incarna (Bartr.) Exell (flag pawpaw), A. longifolia Kral, A. obovata (Willd.) Nash, A. parviflora (Michx.) Dunal (dwarf pawpaw), A. pygmaea (Bartr.) Dunal, A. reticulata Shuttlew. ex Chapman, A. tetramera Small (opossum paw- paw), and A. ×nashii Kral (Kral, 1960). The earliest documentation on pawpaws, which appeared in 1541, was from followers of the Spanish explorer Hernando De Soto, who found native peoples growing pawpaws in the Mississippi Valley (Pickering, 1879). They also used the bark for making fish nets. PLANT DESCRIPTION Pawpaw is a small, deciduous tree that may grow 5 to 10 m high, although the largest known tree is 230 cm in circumference (at 1.5 m height), 18 m tall, and 9 m in spread (American Forestry Association, 1990). In the forest understory, trees often exist in clumps or thickets, which may result from root suckering or seedlings developing from fruit that dropped to the ground from an original seedling tree (Gould, 1939). In sunny locations, trees typically assume a pyramidal habit, straight trunk, and lush, dark-green, long, drooping leaves (Fig. 1) that turn gold and brown during fall (Fig. 2). Leaves occur alternately, are obovate-oblong in shape, glabrous, with cuneate base, acute tip, and prominent midrib, and may be 15 to 30 cm long and 10 to 15 cm wide (Bailey, 1960). Vegetative and flower buds occur at different nodes on the stem, with flower buds being basipetal. Vegetative buds are narrow and pointed, whereas flower buds are round; both are covered with dark-brown, thick pubescence. Flowers emerge before leaves in