Asimina triloba aka Pawpaw

Pawpaw, Asimina triloba, is a deciduous tree in the custard-apple family, Annonaceae. It is native to eastern North America, from southeast Canada through the central and eastern United States. In the wild it grows in rich, moist woods, on wooded slopes, in ravines and beside streams. It is the most cold-hardy member of its genus.

In gardens it forms a small tree or large shrub, usually 15 to 20 feet (4.5 to 6 m) tall and about as wide. Under good conditions it can reach 30 feet (9 m), and wild trees up to 40 feet (12 m) are recorded. It often has several stems and a rounded crown. Root suckers let it spread into colonies or thickets. The bark is smooth and light brown, marked with wart-like lenticels. With age it becomes scaly and fissured. Twigs are reddish brown, and the buds are fuzzy and lack scales. Broken twigs smell unpleasant.

The leaves are large, simple and alternate, 6 to 12 inches (15 to 30 cm) long. They hang in two rows from the stem and have pale undersides. Crushed leaves smell like green bell pepper. They stay green late into autumn, then turn yellow.

Purplish-brown flowers open in spring, from about April to May, before the leaves expand. Each cup-shaped flower is 1 to 2 inches (2.5 to 5 cm) across, with six petals in two tiers. Flies and beetles pollinate them, drawn by a faint fetid smell. The flowers have both sexes but cannot fertilise themselves. A second, genetically different tree is needed for fruit. The fruit is a large berry, 2.5 to 6 inches long, green-yellow at first and ripening brown. It ripens from late summer into autumn. The soft flesh tastes like banana custard, though quality varies between trees.

Pawpaw does best in moist, fertile, well-drained soil that is acidic or neutral. It tolerates occasional wet ground but not soil that stays waterlogged. Full sun gives the most fruit. It also grows in part shade, but deep shade makes it leggy. It suits USDA zones 5 to 9 and rates H4 in the UK. In cooler climates it needs long, hot summers to fruit and may stay shrubby. Young plants are hard to transplant, so buy container-grown stock.

Use pawpaw in woodland edges, wild gardens, rain gardens and damp ground near ponds. It also works as an understory tree in a forest garden. It tolerates black walnut and resists deer moderately. It is the larval host of the zebra swallowtail butterfly. Songbirds, turkeys, squirrels, raccoons, foxes and bears eat the fruit. Gardeners can make rope from the inner bark fibre and a yellow dye from the fruit.

Serious pests and diseases are rare. The pawpaw peduncle borer, a small moth, can destroy many flowers. Zebra swallowtail caterpillars chew young leaves but do little lasting harm. Suckers and fallen fruit can become a nuisance.

The ripe fruit is edible raw or cooked, in pies, preserves and ice cream. Some people get stomach upsets from it. The seeds and fruit skin are poisonous. Handling the fruit or leaves can cause skin rashes, so wear gloves when picking. The plant contains acetogenins. Heavy, regular eating of the fruit has been linked to nerve damage, so eat it in moderation.