Asimina

This page refers to the U.S. pawpaw in the genus Asimina. In some other parts of the world the name pawpaw is applied to the unrelated tropical fruit papaya (Carica papaya).

Pawpaw
Common Pawpaw in fruit
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Magnoliids
Order:	Magnoliales
Family:	Annonaceae
Genus:	Asimina Adans.
Species
See text

Pawpaw (Asimina) is a genus of small clustered trees with large leaves and fruit, native to North America. The genus includes the largest edible fruit indigenous to the continent. They are understory trees found in well drained deep fertile bottomland and hilly upland habitat. Pawpaw is in the same family (Annonaceae) as the custard-apple, cherimoya, sweetsop, ylang-ylang and soursop, and it is the only member of that family not confined to the tropics.

Names

The name, also spelled paw paw, paw-paw, and papaw, probably derives from the Spanish papaya, perhaps because of the superficial similarity of their fruit. Pawpaw has numerous other common names, often very local, such as prairie banana, Indiana (Hoosier) banana, West Virginia banana, kansas banana, Kentucky banana, Michigan banana, Missouri Banana, the poor man's banana, and Ozark banana.

Description

Pawpaws are shrubs or small trees, reaching heights of 2 to 12 m tall. The northern, cold-tolerant common pawpaw (Asimina triloba) is deciduous, while the southern species are often evergreen.

The leaves are alternate, simple ovate, entire, 20 to 35 cm long and 10 to 15 cm broad.

The fetid flowers are produced singly or in clusters of up to eight together; they are large, 4 to 6 cm across, perfect, with six sepals and petals (three large outer petals, three smaller inner petals). The petal color varies from white to purple or red-brown.

The fruit is a large edible berry, 5 to 16 cm long and 3 to 7 cm broad, weighing from 20 to 500 g, with numerous seeds; it is green when unripe, maturing to yellow or brown. It has a flavor somewhat similar to both banana and mango, varying significantly by cultivar, and has more protein than most fruits.

The fruits are quite popular, but the shelf life of the ripe fruit is almost non-existent, for it soon ripens to the point of fermentation. Those who wish to preserve the fruit for the future do so by dehydration, making it into jams or jellies, or pressure canning by using the numerical values for bananas. In southern West Virginia pawpaws are made into a native version of banana nut cake or fruit cake, and baked inside canning jars, the lids heat-sealed to keep the food for at least a year.

• Bark: Dark brown, blotched with gray spots, sometimes covered with small excrescences, divided by shallow fissures. Inner bark tough, fibrous. Branchlets light brown, tinged with red, marked by shallow grooves.
• Wood: Pale, greenish yellow, sapwood lighter; light, soft, coarse-grained and spongy. Sp. gr., 0.3969; weight of cu. ft. 24.74 lbs.
• Winter buds: Small, brown, acuminate, hairy.
• Leaves: Alternate, simple, feather-veined, obovate-lanceolate, ten to twelve inches long, four to five broad, wedge-shaped at base, entire, acute at apex; midrib and primary veins prominent. They come out of the bud conduplicate, green, covered with rusty tomentum beneath, hairy above; when full grown are smooth, dark green above, paler beneath. When crushed they have a scent similar to a green bell pepper. In autumn they are a rusty yellow, which make spotting pawpaw groves possible from a long distance. Petioles short and stout with a prominent adaxial groove. Stipules wanting.
• Flowers: April, with the leaves. Perfect, solitary, axillary, rich red purple, two inches across, borne on stout, hairy peduncles. Ill smelling. The triloba refers to the shape of the flower, which is not unlike a tricorner hat.
• Calyx: Sepals three, valvate in bud, ovate, acuminate, pale green, downy.
• Corolla: Petals six, in two rows, imbricate in the bud. Inner row acute, erect, nectariferous. Outer row broadly ovate, reflexed at maturity. Petals at first are green, then brown, and finally become dull purple and conspicuously veiny.
• Stamens: Indefinite, densely packed on the globular receptacle. Filaments short; anthers extrorse, two-celled, opening longitudinally.
• Pistils: Several, on the summit of the receptacle, projecting from the mass of stamens. Ovary one-celled; stigma sessile; ovules many.
• Fruit: September, October.

Cultivation

Pollinated by scavenging fruit flies, carrion flies and beetles, the flowers emit a weak to no scent which attracts few, if any, pollinators, thus limiting fruit production.

Larger growers sometimes locate rotting fruit or roadkill meat near the trees at bloom time to increase the number of pollinators. Asimina triloba is the only larval host of the Zebra Swallowtail Butterfly.

Species

• Asimina angustifolia Raf. - Slimleaf Pawpaw. Florida, Georgia, and Alabama.
• Asimina incana (W. Bartram) Exell - Woolly Pawpaw. Florida and Georgia.
  • Annona incana W. Bartram
• Asimina obovata (Willd.) Nash - Bigflower Pawpaw. Florida.
  • Annona obovata Willd.
• Asimina parviflora (Michx.) Dunal - Smallflower Pawpaw. Southern states from Texas to Virginia.
• Asimina pygmea (W. Bartram) Dunal - Dwarf Pawpaw. Florida and Georgia.
• Asimina reticulata Shuttlw. ex Chapman - Netted Pawpaw. Florida and Georgia.
• Asimina tetramera Small - Fourpetal Pawpaw. Florida (Endangered)
• Asimina triloba (L.) Dunal - Common Pawpaw. Extreme southern Ontario, Canada, and the eastern United States from New York west to southeast Nebraska, and south to northern Florida and eastern Texas.
  • Annona triloba L.

Cultivation and uses

Asimina triloba is often called prairie banana because of its banana-like creamy texture and flavor.

The pawpaw is native to shady, rich bottom lands, where it often forms a dense undergrowth in the forest. Where it dominates a tract it appears as a thicket of small slender trees, whose great leaves are borne so close together at the ends of the branches, and which cover each other so symmetrically, that the effect is to give a peculiar imbricated appearance to the tree.

Although it is a delicious and nutritious fruit, it has never been cultivated on the scale of apples and peaches, primarily because only frozen fruit will store or ship well. It is also difficult to transplant because of fragile hairy root tentacles that tend to break off unless a cluster of moist soil is retained on the root mass. Cultivars are propagated by chip budding or whip grafting.

In recent years the pawpaw has attracted renewed interest, particularly among organic growers, as a native fruit which has few to no pests, and which therefore requires no pesticide use for cultivation. The shipping and storage problem has largely been addressed by freezing. Among backyard gardeners it also is gaining in popularity because of the appeal of fresh fruit and because it is relatively low maintenance once planted. The pulp is used primarily in baked dessert recipes and for juicing fresh pawpaw drink or drink mixtures (pawpaw, pineapple, banana, lime, lemon and orange tea mix). In many recipes calling for bananas, pawpaw can be used with volumetric equivalency.

The commercial growing and harvesting of pawpaws is strong in southeast Ohio. The Ohio Pawpaw Growers' Association annually sponsors the Ohio Pawpaw Festival at Lake Snowden near Albany, Ohio.

Because of difficult pollination, some may believe the flowers are self-incompatible. Cross pollination of at least two different varieties of the plant is recommended. The flowers produce an odor similar to that of rotting meat to attract blowflies or carrion beetles for cross pollination. Lack of pollination is the most common cause of poor fruiting, and growers resort to hand pollination or to hanging chicken necks or other meat to attract pollinators.

The leaves, twigs, and bark of the tree also contain natural insecticides known as acetogenins, which can be used to make an organic pesticide. Pawpaw fruit may be eaten by foxes, possums, squirrels and raccoons. However, pawpaw leaves and twigs are seldom bothered by rabbits or deer.

This colonial tree has a strong tendency to form colonial thickets if left unchecked.

History

The earliest documentation of pawpaws is in the 1541 report of the de Soto expedition, who found Native Americans cultivating it east of the Mississippi River. The Lewis and Clark Expedition depended and sometimes subsisted on pawpaws during their travels. Chilled pawpaw fruit was a favorite dessert of George Washington, and Thomas Jefferson was certainly familiar with it as he planted it at Monticello. The Ohio Pawpaw Growers' Association lobbied for the pawpaw to be the Ohio state native fruit in 2006; this was made official in 2009.

Medicinal properties

Pawpaw seeds

Growers hope that potential medical use will eventually lead to increased market demand from the pharmaceutical industry.

The seeds also have insecticidal properties. Some Native American tribes dry and powder them and apply the powder to children's heads to control lice; specialized shampoos now use compounds from pawpaw for the same purpose.

Currently, pawpaw extract is being reviewed as an alternative cancer treatment alongside conventional and approved treatments. This is not meant to replace appropriate treatments, but is being examined for acetogenins and ATP production. Because acetogenins vary widely from tree to tree, only standardized extracts are acceptable.[1]

External links

• Flora of North America Asimina
• USDA distribution of Pawpaw
• Pawpaw Information from Kentucky State University
• Asimina Genetic Resources
• Clark's September 18, 1806 journal entry about pawpaws
• Links to research on pharmaceutical uses of paw paw
• Asimina triloba - Brooklyn Botanical Garden
• Asimina Genetic Resources - Pawpaw