II. Characteristicsof the Pawpaw: The Pawpaw is a deciduous tree which requires little pruning to maintain its shape. It grows to a height of about 20 feet. The tree produces a maroon upside-down flower in the axils of the last year's leaves. The flowers are about 2 inches across and bloom occurs between March and May depending upon cultivar and climactic conditions. Each flower is capable of producing several fruits because the flower contains several ovaries. The leaves of the pawpaw are dark green and oblong and can reach 1 foot in length! They turn yellow in autumn and the tree leafs out again in the spring after bloom. The fruit is the largest fruit native to America. The fruits can weigh up to 16 ounces and are up to 6 inches in length (the fruit size and weight does vary by cultivar).
 

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Pawpaw fruit cluster

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Pawpaw fruit cluster

Pawpaw trees are hardy to USDA climate zone 5. During the winter months the tree enters a deep dormancy. The roots as well are dormant, rare among deciduous trees, so transplanting should be done in the spring after the tree has broken its dormancy, otherwise damage to the roots may result in fungal infections and root rot. Transplanting can be trickey as pawpaws have extremely long taproots. Nurseries often offer seed;ings or grafted named cultivars. Chose plants that have been raised in a container, this way the integrity of the taproot is reasonably ensured.

Pawpaws must be cross pollinated for fruit to set. Plant at least two trees with different genotypes (ie. two different cultivars or seeds from two different trees). Pollination is carried out by flies and beetles. Bees seem to be uninterested in the flowers of the pawpaw. Pawpaws are easily propagated by grafting, but softwood and hardwood cuttings are difficult to root. Pawpaws may be grown from seed, provided the seeds are properly stratified.
 

For more on growing Pawpaws:

planting guide 1,

IV. Pests: The pawpaw tree has few pests.

Asimina spp. are the larval host for the Zebra Swallowtail, Eurytides marcellus (Cramer) (IFAS , USGS links). North of Florida, Asimina triloba is the exclusive host for the caterpillar. The caterpillar rarely feeds on the foliage in numbers great enough to reduce the yield.

The pawpaw peduncle borer, Talponia plummeriana, may be the most severe pest (USNM image).  The larvae, which reach a length of 5 mm, feed in fleshy parts of the flower, causing flowers to drop.

A leafrolling caterpillar, Ompalocera munroei, can be damaging to young trees (Blossom Nursery link).

An FAO site lists pawpaw fruit fly (or papaya fruit fly), Toxotrypana curvicauda (USDA web page, image),  as a pest in Florida and Venezuela, pawpaw whitefly (or papaya whitefly), Trialeuroides variabilis, and a spider mite, Tetranychus seximaculatus, are listed as pests as well.  Several closely related species of hornworms (Sphingidae) may feed on foliate (Erinnyis obscura in Jamaica, E. ello in Venezuela, E. alope in Florida).

Other predators of the fruit include raccons, squirrels, foxes and mice. Deer, rabbits, and goats do not feed on leaves and twigs. This may be due to the anti-cancer and pesticidal properties of the leaves and twigs.