Pawpaws are flexible in their soil requirements. The main thing is good drainage. The soil must be well drained. Soil pH should be moderately acid to neutral, in the range of 5.5 to 7.0. Pawpaws are happiest in a rich, deep, loamy soil with high organic matter content. In addition, they appreciate an organic mulch. In the wild, a natural mulching layer of decomposing leaves is normally present. Excessively dry sites should be avoided. Moist soils are ideal.
Pawpaws are native to the humid temperate climate of eastern North America. They are hardy to at least -20° F (-28° C). They require a approximately 400 hours of chilling to break dormancy. This requirement varies with provenance: pawpaws of northern origin require more chilling than cultivars of southern origin. Hence, pawpaws grow best in USDA Hardiness Zones 5-8. www.usna.usda.gov/Hardzone/.
They need a minimum of 30 inches (~75 cm) of rainfall annually with the majority of that falling in spring and summer. They need a long warm summer to ripen the fruit -- at a minimum 150 frost-free days and 2200 GDD (Growing Degree Days).
Site and Spacing
The pawpaw is a small tree that typically grows to about 20 feet high and less broad. In an orchard setting, tree centers should be at least 10 feet apart. Row widths depend on the size of tractors and equipment -- 20 foot rows may be a minimum width. When raising just a few trees for fruit, it is advisable to plant them close -- no further than 30 feet apart -- in order to ensure good pollination, as the flowers are insect pollinated and as the trees are self infertile. For good fruit production the trees should be grown in full sun. While it is true that pawpaws are shade tolerant, they will fruit much less in the shade. Because of the large size of the leaves, windy sites are damaging and to be avoided.
Establishing Young Trees
Prepare the soil in advance of receiving your young pawpaw tree. The soil from the hole should be thoroughly loosened to a fine tilth. The hole should be the same depth as the root system, and 2 or 3 times the diameter of the root mass. In an orchard setting, we recommend you plow a furrow down the row, rototill the soil to a loose tilth, and then mound the soil into raised beds. Pawpaw trees do not have fibrous roots. Their roots are fleshy, similar to magnolia. And like magnolia, pawpaws transplant better if moved in the spring, not the fall. However, container grown stock can be planted virtually anytime during the growing season. For the first growing season keep the trees well watered. Do not overwater, however. Drowning the tree is bad. Keep the area completely free of weeds & all competing vegetation up to a 2-foot radius. Weed control is essential to successful establishment. Pawpaw is almost the last tree to leaf out in spring, a trait reflecting its tropical origins. The young leaves often appear chlorotic. Don't worry. This is a temporary springtime condition. Chlorosis on mature leaves is a different matter, however.