Neal Peterson, founder of the non-profit PawPaw Foundation, says pawpaw trees are generally self-incompatible�requiring a genetically different tree for successful fertilization and fruit set to occur. In the wild, pawpaws often spread by root suckers and form groves of trees with identical genotypes. Additionally, natural pollinators of pawpaw flowers�bees, flies, and other insects�are not always dependable or available. Trees in a wooded setting are also often heavily shaded and thus less vigorous than trees in the open.
To improve fruit set, Peterson recommends thinning trees around the pawpaws to provide more light, transplanting wild pawpaws from other areas of the woods to offer genetic variability, and hand-pollinating pawpaw flowers when they bloom in early spring. But the best way to ensure the development of quality fruit, Peterson says, is to purchase grafted clones of several pawpaw cultivars and plant them in an area where they will receive full sun.