Spring is a time of swelling buds and wildflowers in Illinois forests. However, the flowering display of some plants may be overlooked if you aren’t observant.
The tiny, indiscrete flowers of pawpaw (Asimina triloba) are often unnoticed by humans since they appear in early spring, prior to leafout. Although quite beautiful, the minute, 1 to 1 ½ inch flowers are an interesting shade of maroon to purple-brown in color and persist for about a month, typically emerging sometime around mid-April. These specialized flowers are also overlooked by many of our common, native pollinators.
Pawpaws are pollinated by flies and beetles instead of bees, which pollinate many of our common food crops. The faint (or often non-existent) scent of the pawpaw flower mimics the smell of rotting meat. These plants evolved with flowers to attract blowflies or carrion beetles who naturally feed on dead and decaying animals. This pollination strategy is more common among tropical plants, but rare among our native, more temperate species.
Pawpaw exhibits other features of tropical plants including specialized “drip-tips” on their leaves to help wick away water, which is a feature common among tropical plants to clear away moisture that can promote development of fungal diseases on foliage. The palm-like appearance of almost foot long pawpaw leaves is also reminiscent of the tropics.
Pawpaw is the northernmost species of the Annonaceae Family, or custard apple family. Most other members of this plant family are concentrated in the tropics. Although pawpaw is native to Illinois, it doesn’t span the entire state. It is prevalent in southern and central Illinois, but its distribution tapers off in our northern most counties.
The earliest fossil evidence of Asimina triloba originates in the Miocene (about 23 to 5.3 million years ago). At several points across the geologic time scale since the Miocene our climate has warmed and tropical areas have expanded, subsequently expanding the range of the Annonaceae family. In addition, scientist have hypothesized that many large fruits of Central America were dispersed by megafauna that was extinct by the end of the Pleistocene (2.6 million to 11,700 years ago). These factors, among others, resulted in a plant like pawpaw, which evolved in a more tropical setting, to call our temperate Midwest climate home today.
There is evidence that humans played a role in pawpaw dispersal as well. One of the earliest records of pawpaw is from Hernando de Soto’s expedition to the Americas in 1541. A Portuguese officer on the expedition notes that Mississippi Valley Native Americans were cultivating and eating pawpaw. Given this and other accounts of pawpaw use by Native Americans (some dating back over 10,000 years), it is likely that an often nomadic lifestyle and trade with other tribes resulted in greater distribution of pawpaw prior to European settlement.
Post-settlement, our forefathers also cultivated pawpaw, with both George Washington and Thomas Jefferson including pawpaw plantings in their agricultural practices. Interestingly, pawpaw is noted to have sustained the Lewis and Clark expedition for a few weeks when rations were lean, although these fruits were certainly harvested from the wild.
Pawpaw fruits, which are the largest native tree fruit in North America, ripen in the fall to producing 3 to 6 inch long fruits. The fruit is soft textured when ripe and has a flavor similar to banana, although some people also compare the taste to papaya, which is likely the tree’s namesake. Due to the extremely short shelf life of this fruit (2-3 days), large scale commercial production has been overlooked. However, more productive varieties of this fruit tree have been developed and are for sale commercially to home growers.
If you are interested in adding a native taste of the tropics to your home garden, consider planting a few pawpaw trees this year. The attractive, small trees mature to about 15 or 20 feet in height and do well in partial shade to full sun, with young seedlings benefitting from more shade early on. I suggest selecting a developed commercial variety, typically propagated by grafting, to ensure adequate production of good-tasting fruit. Be sure to plant more than one variety of pawpaw as cross-pollination is required for fruit development. Before long, you can enjoy the home-grown taste of our largest native tree fruit.