Asimina triloba (L.) Dunal

Pawpaw

© SRTurner

Family - Annonaceae

Habit - Small trees, usually strongly colonial from root suckers.

Stems - To 10 m. Bark gray, usually with white to light gray patches, thin, smooth, becoming roughened (warty) or rarely scaly on older trees. Twigs light to dark reddish brown, glabrous or sparsely hairy, the buds lacking scales, reddish brown, hairy, the terminal bud flattened and narrowly ovate in outline, the lateral buds nearly globose.

	Bark of medium-aged tree.
© DETenaglia

	Winter twig.
© DETenaglia

Leaves - Alternate, simple, petiolate. Petiole 5-20 mm long. Stipules absent. Blades 10-35 cm long, oblanceolate to oblong-obovate, narrowed or tapered at the base, abruptly tapered to a short point at the tip, glabrous at maturity (hairy when very young), the veins prominent, the margins entire, the upper surface green and usually shiny, the undersurface pale green.

© DETenaglia

	Winter bud.
© DETenaglia

Inflorescence - Flowers solitary at the nodes of the second year's growth along branches, produced before or as the leaves develop.

Flowers - Perfect, hypogynous, on short, hairy stalks. Sepals 3, 8-12 mm long, broadly triangular, sharply pointed, green, usually hairy, shed early. Petals in two unequal and strongly overlapping whorls of 3, the outer series 2.1-2.7 cm long, broadly ovate, the tips spreading and curled outward, the inner series 1.0-1.4 cm long, ovate, erect or with the tips somewhat spreading, the surface of both series with prominent veins, red-brown to maroon at maturity (green when immature), hairy on the outer (under) surface, the inner series with nectar-producing glands at the base of the inner surface. Stamens numerous, small, free, densely packed around the elongated receptacle, not clearly differentiated into an anther and filament. Pistils 3-5, hairy, with 1 carpel, the ovary superior and with 12-16 ovules, the style short, the stigma globose.

	Sepals.
© SRTurner

	Young flowers.
© DETenaglia

	Mature flower (from below).
© DETenaglia

Fruits - Berries, single or 2-4 in a spreading or drooping cluster, 4-13 cm long, ellipsoid to cylindrical, somewhat irregular, rounded at the ends, pale green, turning yellowish and then brownish black with age. Seeds 2-10, 2.0-2.8 cm long, flattened, elliptic-ovate in outline, dark brown, shiny, embedded in a light yellow edible pulp.

	Fruit cluster.
© SRTurner

	Seeds in (very) mature fruit.
© SRTurner

Flowering - March - May.

Habitat - Understory tree in bottomland and mesic forests, along streams, ravines, base of bluffs.

Origin - Native to the U.S.

Lookalikes - None when in flower.

Other info. - This common tree can be found throughout most of Missouri, and most of eastern half of the continental U.S. as well as Canada. The tree is recognized by its strongly colonial habit, smooth gray bark, and large leaves which are broadest above the midpoint. The deep maroon flowers are also unique.

Pawpaw is an aromatic species. Crushed leaves emit an aroma described as similar to motor oil or rotten bell peppers. The flowers are said to smell like fermenting grapes. The fruits are not only scented but also edible and prized, at least by some individuals, as being very tasty. The flesh texture is creamy and custardlike, and with a flavor not unlike banana. Other individuals, however, may find the odor and flavor nauseating, or even to cause vomiting due to a mild allergic reaction. Finding ripe fruits can be challenging, as fruit set appears to be highly variable, and the fruits are also scavenged as a food source by arboreal mammals such as squirrels. Legends persist that the flowers are pollinated by carrion flies, and a technique proposed to increase pollination is to hang rotting meat nearby to attract additional flies. Another reason for low fruit set is that the plants are obligate out-crossers. Since many pawpaw groves are clonal colonies, fertilization cannot occur unless genetically distinct individuals are also present in the vicinity.

Although pawpaw fruit flesh is edible, the seeds are poisonous. These and other parts of the plant contain alkaloids and acetogenins.

Photographs taken at the Kansas City Zoo, 5-1-00, in Brown Summit, NC., 3-23-03, and at Whetstone Conservation Area, Callaway County, MO., 2-25-04 (DETenaglia); also at Engelmann Woods Natural Area, Franklin County, MO, 4-12-2010, Glassberg Conservation Area, Jefferson County, MO, 5-9-2013, and along the Meramec River near Glencoe, St. Louis County, MO, 7-17-2017 (SRTurner).