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~ The Pawpaw, Asimina triloba ~

...not to be confused with the Papaya!

Hardy to zone 5 and a native of North America, Asimina triloba is a member of a largely tropical plant family (the Annonaceae) that includes the soursop, sweetsop and the custard apple.

The large, nutritious fruit has a wonderful, and unique aroma blending dairy cream, bananas and pineapple, and its surprising texture is like a perfectly smooth custard. The big, shiny brown pits just slip out of this custard, and aren't held by any structure. The tree is very pest-resistant and requires no spraying; in fact, scientists all over the world are busy analyzing the natural substances (called annonaceous acetogenins) in the leaves and bark that are responsible for repelling both insects and fungus. Interestingly, crushed leaves have a faint, but distinct odor of petroleum. The tree's only theoretical "enemy" in Canada would be is the Zebra Swallowtail Butterfly Eurytides marcellus caterpillars. This magnificent butterfly's relationship with the Pawpaw is much like that of the Monarch with the milkweed. Its caterpillar must feed on the leaves of the Pawpaw, it has no alternate host. The butterfly is rare in Canada and the caterpillar, should it appear, ought to be considered a blessing.

Why have people have never heard of this amazing fruit? In one word, transport. The fruits are too soft to withstand shipping, and bruising the peel (which does not bruise the "custard" within) gives off a very strong odor of perfectly ripe pineapple which may be a bit intimidating in our bland supermarkets.

The only way to taste fresh pawpaws is to grow them oneself.

Besides its value as a fruit tree, and host to an interesting butterfly larva, the pawpaw is an attractive tree that matures at the height of lilacs, and is therefore well-suited for planting beneath electrical or telephone wires without fear of damage from falling branches. Big, healthy drooping leaves and gold fall colours add to the general interest. The fruits ripen on the tree, in the fall. They become light green, may develop a yellow tinge, and like a banana, develop brown specks. They are ready when they begin to yield to gentle pressure, and become aromatic.

They are very perishable, and will last no more than 2 days at room temperature, on one week in the refrigerator.

The fruits are primarily eaten fresh, cut in halves and scooped with a spoon. The heat of cooking causes loss of the pawpaw's volatile flavour compounds, so they are best incorporated in ice cream, mousses and gelatin-based chiffon pies.


Cultivation



Climate
Pawpaws are reliably hardy in zone 5.

Site, Soil and Habit
In its natural habitat, the pawpaw is an understory tree. It is capable of fruiting in the shade, although yields are higher with greater exposure. In cultivation, it has a stringent requirement for shade as a seedling; full sun is deadly. They prefer a slightly acidic soil, but are generally tolerant of a wide range of pH values. They do not like heavy, water-logged soil, and should be given plenty of water while maintaining good drainage. The leaves are held almost vertically off the branch, giving the tree an exotic appearance. Fall foliage colour is an attractive gold.

Propagation
Pawpaws seeds should not be allowed to dry for long periods. The require 60-120 days of cold stratification, and are slow and erratic to germinate. While the very long tap root may take 20 days after stratification to emerge from the seed, the leaves may take over two months to appear. Growth of the seedlings is slow for the first two years, and fruit are borne on trees >2m. The trees sucker and eventually form a thicket. These suckers are not good transplant material as they resent transplantation. Spring transplanting is preferred.

Pollination
Unusual, drooping reddish-brown flowers open before expansion of the foliage in the spring. They are of little ornamental value. Pawpaws are protogynous, that is, the stigma (female part) ripens before the anthers (pollen-bearing), and is self-incompatible. Therefore, two tree are required in order for fruit to be produced. The natural pollinators (flies and beetles) are not particularly efficient, and hand-held pollination with a paint brush is important for good fruit set.


The Natural, Secret Ingredients in Pawpaw Flavor



Compound

Taste in Water Odor

Acetoin acetate Milky, soft, weak, sweet, buttery, melon flesh-like. Powerful, ethereal, sweet, acetoin-like, yogurt-like.

Acetoin butanoate
(detected in nature for the first time)
Butery, fruity, creamy, estery, sweet, pear-like. Fruity, sweet coarse, buttery, burnt sugar note.

Acetoin hexanoate
(detected in nature for the first time)
Milky, fruity, oily wet, fermented, fresh gree, apple-like, pawpaw-like. Fruity, pineapple-like, quince-like, reminiscent of hard flesh.

Acetoin octanoate
(detected in nature for the first time)
Oily, juicy, fruity, spicy, powerful, pear-like, fermented. Oily, fermented.

Butane-2,3-diol monobutanoate Fruity, mild, succulent, weak, apple-like, Muscat-like, Japanese Pear-like, Walnut-like. Sweet-sour, succulent, fruity.

Butane-2,3-diol monohexanoate Fruity, succulent, powerful, powdery, dusty, buttery, coarse, woody, rum-like, apple peel-like, green. Buttery, succulent, fruity.

Butane-2,3-diol monooctanoate Wet-fatty, weak, soft, cool, fresh milk-like, blue-cheese-like, slightly astringent. Cool, milk-like, baked bread-like.

Reference: Shiota,H. 1991. Volatile components of pawpaw fruit [Asimina triloba (L. Dunal)].
J. Agric. Food Chem. 89: 1631-1635.


Pawpaw Links

Pawpaw Information Web Site - Comprehensive site maintained by the Kentucky State University (KYSU). THE Pawpaw site.
California Rare Fruit Growers - Provides information for commercial and hobby fruit growers.
Northern Nut Growers Association - Great variety of information and links.
Ohio's Pawpaw Festival - Yearly event.
Integration Acres - Fresh pawpaws, pawpaw chutneys, frozen pulp ans salsa.
Grimo Nut Nursery - Canadian supplier of Pawpaw tree seedlings.

Click to enlarge

Earwig damage on growing leaves

Earwig damage on mature leaves

pawpaw flesh close up
Closeup of pawpaw flesh.

bowl of pawpaws
A bowl of fresh pawpaws.

asimina triloba pawpaw fall color
In autumn, the pawpaw's drooping leaves turn bright yellow.


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