Jennifer Schultz Nelson
Extension Educator, Horticulture
One of the great parts of my job is that not only do I work with a subject I love, I get to surround myself with people who also love plants and gardening-- the Master Gardeners. I am always learning something new from them.
About a month after I began working for U of I Extension, I took a tree identification class with Master Gardeners from all over central Illinois. A Master Gardener in my class was telling us all about how wonderful pawpaw fruit was. Many of us, including myself, had never eaten it.
He brought some in for us to try, and it was delicious. It tasted like a combination of banana and mango or peach. I really wanted to grow these fruits in my yard. A little research has shown me pawpaw may not be the best choice for my landscape.
The pawpaw, Asimina triloba, is the largest tree fruit native to the United States, and is native to the woodlands of the Eastern U.S. There are other species in the Asimina genus, but only Asimina triloba can survive the cold winters of our temperate climate, all the way to Zone 5.
Our hot and humid Illinois summers aren't a problem for the pawpaw. In fact, the more hot and humid, the better. They do not grow well where it is too dry or too cool in the summer. Pawpaws are rarely found on the Atlantic or Gulf coasts because the summers are too cool.
Pawpaw fruits grow on the pawpaw tree, which ranges in size from 12 to 20 feet tall. The tree itself grows in a narrow cone shape, which is generally pleasing for most landscapes. The drawback is that it is prone to root suckering. If these suckers are not removed, a pawpaw grove or patch develops which is technically made up of clones of the original tree, since all the suckers arise from that tree.
It is hard to transplant a pawpaw tree because it has a thick taproot. Trees are usually planted when quite small, and need protection from full sun until they are a year or two old. They also require moist, but well drained, slightly acid soil. Heavy, wet, clay soil should be avoided for best growth.
The leaves on a pawpaw are huge-- up to 12 inches long! They are oblong in shape, and smell like a green pepper when crushed. Their large size makes them look somewhat tropical. They are very prone to wind damage due to their large size.
Pawpaw flowers on the other hand, are relatively small, only an inch or inch and a half wide and purple-brown in color. They appear just before the leaves in the spring and hang upside down. Each flower has six petals and multiple ovaries. Each ovary can produce its own fruit, which explains how a single flower can produce a cluster of up to nine fruits.
Each flower must be pollinated to produce fruit. The flowers are perfect, containing both male and female reproductive parts, but they cannot self pollinate-- so another unrelated tree must be nearby.
Complicating the situation further is that bees, which pollinate many of our food crops, show no interest in pawpaw flowers. Pollination is left to flies and beetles. I read one source that suggested putting rotting meat around your pawpaw tree in bloom to attract flies to pollinate the flowers. Boy that would be something to try and explain to the neighbors! The other, less smelly option is to use a small paint brush to hand pollinate the flowers. But that sounds like an awful lot of work!
Each individual pawpaw fruit weighs anywhere from 5 to 16 ounces, and is from 3 to 6 inches long. It looks a lot like a mango. The fruits contain 10 to 14 black-brown seeds that are shaped like lima beans. They ripen anywhere from mid-August to October, and are soft when ripe.
Pawpaw fruit is best eaten fresh soon after harvest, as it has a shelf life of only 2 or 3 days. This short shelf life has limited the fruit's commercial uses, although Kentucky State University is leading research to try and develop cultivars suited to commercial fruit production.
There is also research evidence that pawpaw leaves and twigs contain compounds with anti-cancer and pesticidal properties. These findings may lead to other commercial uses besides the fruit.
When selecting a pawpaw tree for your landscape, choose named cultivars to be sure of fruit quality. While it is possible to germinate pawpaw seeds, there is a very good possibility that the resulting seedling will produce poor fruit. Purchasing named cultivars, typically propagated by grafting, will ensure that you are growing a tree which will produce good-tasting fruit.
I haven't planted a pawpaw tree in my yard yet. I am not convinced it would grow well there. The soil has a lot of clay and does not drain well everywhere, which is not good for pawpaw. Also, it is extremely windy at our house, which would shred the pawpaw's leaves in an afternoon.
Besides these factors, in order to get fruit I would need to plant at least two trees-- and I really don't have the room to plant two more trees. My husband would be shocked to hear me admit that we don't have room to plant another tree. He likes to accuse me of having eyes bigger than the garden!
I will always be thankful that that Master Gardener introduced me to pawpaw fruit, even if I never get to grow my own tree. If you love gardening and would like to learn more about gardening while giving back to your community, consider joining our 2009 U of I Extension Master Gardener Training Class. Class begins in January 2009. Call (217) 877-6042 for more information.