New York Metropolitan Flora

Common Names

Pawpaw, Custard Banana, False Banana

Field Identification

Pawpaw is a native, deciduous, large shrub or small tree. It exhibits clonal growth, forming thickets or small colonies. Crushed leaves and freshly cut wood are aromatic, smelling somewhat like turpentine. The terminal naked buds show the juvenile leaves covered with a dense, rusty tomentum. Axillary buds are large, globose, and covered with a rusty tomentum. The leaves are large (up to 1 ft long) and "tropical"-looking. Leaf blades are oblong to obovate with entire margins. The flowers are green, then turn brownish purple, and are 2-5 cm broad, bell-shaped, and pendant. Flowers emerge along previous years' stems in the spring before the leaves. The fruit is a large berry, 4-10 cm long, green then turning yellow, then brown or black at maturity.

There are no related species in our area, and no potentially confusing species.

Food uses

 Disclaimer: The information provided here is for reference and historical use. We do not recommend nor do we condone the use of this species for food purposes without first consulting a physician.

(Sullivan, 1993) (Elias, 1982) (Mitchell, 1979) (Bonner, 1974) (Kral, 1960)

Fruits are fleshy and edible. The pulp is whitish to yellow and custardy in texture, with a taste and texture at maturity like a sweetish avocado. The white-fleshed varieties of fruit are apparently less palatable, while those with yellow to orange flesh are tasty. Pawpaw fruit can be consumed by humans, although handling the fruit may cause allergic reactions in sensitive individuals. The fruits can be eaten raw and cooked for puddings.

Medicinal uses

 Disclaimer: The information provided here is for reference and historical use. We do not recommend nor do we condone the use of this species for medicinal purposes without first consulting a physician.

(Sullivan, 1993) (Mitchell, 1979)

Seminole Indians reportedly make a tea from the flowers to help kidney discomfort. An anticancer drug has been purified from pawpaw and is being tested. The seeds contain an alkaloid, asiminine, which is reported to have emetic properties. The bark also contains an alkaloid, analobine, and was once used as a medicine.

Other uses

 (Brett, 1992) (Mitchell, 1979)

Bark of young twigs is sometimes used by fishermen as a stringer for the catch. Pawpaw is an attractive foliage landscape tree with a luxuriant, tropical appearance. The leaves turn yellow in fall.

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Poisonous properties

Disclaimer: The information provided here is for reference and historical use. If you believe you have been poisoned, please contact the Poison Control Office near you (look for the number in the front of the phone book).

(Sullivan, 1993)

Handling the fruit may cause allergic reactions in sensitive individuals. The seeds contain alkaline asiminine, an emetic and narcotic.

Nomenclature

Description

HABIT Perennial, deciduous tree or shrub 1.5-11(-14) m tall, monoclinous.

STEMS Main stems ascending, round. Bark grayish-brown, furrowed on larger specimens, not exfoliating, new shoots with smooth bark. Branches ascending. Twigs grayish-brown, odoriferous, terete, smooth, moderately densely to densely pubescent apically with rust-colored hairs, glabrescent. Pith white to brown, round, continuous.

BUDS Terminal and axillary buds present, dimorphic, scattered along stem. Terminal bud linear-conical, 5-8 mm long, pointed, bud scales absent. Axillary buds solitary, globose, 2-5 mm long, blunt, bud scales 2-4, brown to black, imbricate, ovate, chartaceous, acute, densely pubescent throughout with rust-colored hairs, not glabrescent. Bud scale scars not encircling the stem. Leaf scars crescent- to U-shaped, 2-5 mm high, 3-5 mm wide, prominent. Vascular bundle scars 5, elliptical.

LEAVES Alternate, simple, distichous, spaced somewhat evenly along stem, divergent from stem. Stipules absent. Leaves petiolate, petiole furrowed, 0.5-1 cm long, moderately densely pubescent throughout, not glabrescent. Leaf blades: abaxial surface light green, adaxial surface green, oblanceolate to elliptic to obovate, bilaterally symmetric, (10-)14-27 cm long, 5-9.5(-12.5) cm wide, membranaceous, base attenuate-cuneate, margin entire (sometimes scarecly revolute), apex acute to acuminate. Abaxial surface with long and unbranched appressed unicellular rust-colored hairs, sparsely to densely distributed throughout, glabrescent. Adaxial surface glabrous or with long and unbranched appressed unicellular rust-colored hairs, sparsely distributed mainly along midveins, glabrescent. Venation brochidodromous or eucamptodromous, lateral veins 10-19 pairs. For a study of leaf thickness and stomatal distribution and size see Carpenter & Smith, 1981; Carpenter & Smith, 1975.

INFLORESCENCES Precocious, formed on last season's growth, single axillary flowers. Peduncle 1-1.5 cm long. Bracts sessile, ovate, deciduous, 4 mm long, 2 mm wide, base truncate, margin entire, apex acute, adaxial surface pubescent.

FLOWERS Bisexual, with sepals and petals readily distinguishable from one another, 3-merous, 20-25 mm long, 20-40 mm wide, with faintly fetid aroma, perianth of more than two whorls. Calyx stereomorphic, acetabuliform, of free sepals, deciduous, abaxial and adaxial surfaces purple-brown at maturity, 10-14 mm long. Sepals 3, ovate to triangular, 10-14 mm long, 10-14 mm wide, base truncate, margin entire, apex acute, abaxial surface sparsely to moderately densely pubescent apically with reddish-purple hairs, not glabrescent. Corolla stereomorphic, campanulate, of free petals, deciduous, abaxial and adaxial surfaces purple-brown, 20-25 mm long, 20-40 mm wide. Petals 6, elliptic to widely elliptic to widely oblong, petals of outer and inner whorls dissimilar. Outer petals 17-25 mm long, 14-19 mm wide, base obtuse to truncate, margin entire, apex acute and slightly to conspicuously recurved, abaxial surface pubescent, adaxial surface glabrous. Inner petals 10-15 mm long, 8-11 mm wide, corrugated within, base hastate and saccate, margin entire, apex acute and recurved, abaxial surface glabrous to pubescent, adaxial surface glabrous. Gynoecium apocarpous. Carpels 3-7(-10), fusiform, appressed red-hairy. Locules 1 per carpel. Stigmas 1 per carpel, capitate. Styles absent. Ovary superior, 3-4 mm long, 1 mm wide. Placentation marginal, ovules in two ventral rows. For a study of developmental morphology of the ovule see Lampton, 1957. Androecium globular, ca. 8 mm broad at anthesis. Stamens many, 1-2 mm long, short-columnar, joined into a ball on the elevated receptacle. Anther sacs joined into two parallel series on outer stamen face and surmounted by blunt to subspherical connectives, dehiscing along the long axis for entire length of anther, unithecal/bisporangiate, orange to yellow, glabrous. Filaments straight, yellow, orange to brown, glabrous, reduced. For a study of microsporogenesis see Locke, 1936. Staminodes absent. For a study of the vascular anatomy see Smith, 1928.

FRUITS Baccetum, yellowish-green to brown when ripe. Individual monocarps oblong-cylindric to globular, 31-70 mm long, glabrous. For a study of fruit anatomy/morphology see Rao, 1982.

SEEDS 2 to 10, brown, bean-shaped, somewhat laterally compressed, 14-27 mm long, 9-18 mm wide, testa smooth, endosperm ruminate. For a study of seed anatomy/morphology see Rao, 1982.

Habitat

Rich mesic hardwood forests and river bottoms.

Rarity Status

Heritage global rank -- G5

Connecticut -- Not listed

New Jersey -- S1

New York -- S2

Species Biology

May

Pollination

(Wilson, 1980) (Zimmerman, 1941) (Roberston, 1896) (Kral, 1960) (Wilson & Schemske, 1980).

Sapromyiophilous: Potential pollinators are flesh-flies and beetles, but the exact pollinating agents of Asimina are not known. Many flies were observed on flowers of plants studied in cultivation in Italy. Fruiting is not abundant in nature, and experiments show that fruit set is pollen-limited. Hand pollination is necessary to produce fruit on trees in cultivation.

Fruiting

Summer

Dispersal

(Sullivan 1993) (Bowden, 1951) (Cypher & Cypher, 1999)
Endozoochory, pawpaw fruits are consumed by many birds and mammals, including raccoons, gray foxes, opossums, squirrels, and black bears.
Hydrochory, both fruit and seeds float, so water dispersal is also possible.

Germination

(Wilson, 1980) (Bowden, 1951) (Brett, 1992) (Kral, 1960)

Recalcitrant, prechilling required: Germination is slow. It can be accelerated by refrigeration (stratification) after which development of the hypocotyl and epicotyl still requires several weeks. According to Brett (1992), seeds should not be allowed to dry out before planting. Place seeds in polyethylene bags with damp sphagnum moss and cold-stratify at 2-4º C for 60--100(--150) days. Following this treatment, the rate of germination can be improved by adding bottom heat (27-30º C) and shading.