One of the most delicious home orchard fruits, pawpaw (Asimina triloba) is native to eastern North America and is its largest edible native fruit. The small 15- to 20-foot deciduous tree produces oblong green fruit that taste like a combination of mango, banana, pineapple and papaya. Pawpaw belongs to the tropical custard apple family and is the only member that grows in a temperate climate. You need at least two different unrelated trees for fruit to set.
Pawpaws are suited for home orchards because they don't get too large and because they give a fruit that is seldom marketed. The large dark-green leaves can be 12 inches long and have a tropical look. They turn yellow in mid-autumn. The tree is late to leaf out in the spring, with leaves appearing after flowering. An average-sized 7-year-old tree gives 4 to 14 pounds of fruit, and mature trees yield up to 35 pounds of pawpaws. Pawpaws grow in U.S. Department of Agriculture plant hardiness zones 5 through 9.
The 2-inch wide maroon pawpaw flowers appear during March to May, depending on the variety, geographic location and weather conditions. The flowers grow on last season's growth. The rounded buds covered with brown fuzz hang downward, and the blooming period lasts for three to four weeks. Young grafted trees can start flowering at three years old, but don't usually set fruit until they are five to six years old. The flowers have an inner and outer set of three petals each. The fragrance isn't a typical floral scent, but is a yeasty to fetid smell.
To get a good crop of fruit, you'll need to hand-pollinate the flowers. The unusual floral scent and flower color are meant to attract flies and beetles instead of bees, and often there aren't enough pollinators around in the early spring. Collect pollen from one variety to use on a different variety. Look at the middle of the flower to locate the central green female pistil surrounded by the male pollen-producing anthers. With an artist's brush, collect yellow pollen from the anthers when they are brown and crumbly-looking. Transfer the pollen to a flower of another pawpaw tree that has a receptive green, glossy, sticky-surfaced stigma. The stigmas are receptive before the pollen is produced, so locate newly opened flowers to pollinate. Save collected pollen in a vial for later use if your varieties don't bloom at the same time.
Each flower has several ovaries at its base and can produce as many as five fruits in a cluster that resembles a loose hand of bananas. Usually, hand pollination gives a heavy fruit set and you may need to thin the fruits. The pawpaws begin to ripen in August. Since the flowers had a staggered blooming time, the fruits don't all ripen at once, even those in the same cluster, and ripening can extend over three to four weeks on a given tree. Test for ripeness by pressing gently on the stem end of the fruit. If it gives slightly and the fruit has a pronounced rich fragrance, it is ripe.