North America's largest native fruit, the pawpaw, commonly grows in bottomlands and along creek banks in well-drained soil. Pawpaws usually form the understory of hardwood forests, growing tall and slender to heights of about 25 feet with widely-spaced thin branches. In full sun and under cultivated conditions, the pawpaw's shape becomes pyramidal and shorter. Pruning helps maintain the tree's health but should be done sparingly.
Pruning the pawpaw as soon as the tree is transplanted may be necessary. Pawpaws for home, garden and commercial orchard are cultivars grafted to seedlings. Because the young trees may be killed by direct sunlight, transplanting to open ground often takes place in the third year of growth. Pawpaw roots have few root hairs and break easily. To compensate for lost roots, use pruning shears to clip branches back by about 1/3 of their length. Trim off dead wood close to the junction of the growing part of the tree later in the season.
Pruning pawpaw trees as they approach their first bearing season, at 5 to 7 years old and about six feet tall, should be kept to a minimum. In full sun, the trees form shorter and more numerous branches than pawpaws naturally do in shade. Shaded trees grow tall with a very open canopy. Inspect the trees in late winter for crossed limbs. Remove the weakest of the pair by clipping at the trunk or the junction with the main branch. Remove only as much as is necessary to prevent bark damage.
Because pawpaw branches are weak, pruning could involve thinning clusters of fruit that are too heavy for the branch to bear. Clipping the smallest fruit from a cluster with pruning shears causes little damage to the tree and lightens the branch's load. Because pawpaws seldom pollinate well, heavy fruiting usually results from hand pollination of flowers. Avoid this extra pruning by skipping some blossoms, or let nature do the work.
After strong storms, check the pawpaw trees for wind damage. In exposed locations, broken limbs due to high winds could be a frequent problem. Remove broken limbs with pruning shears or limb loppers by cutting just below the break. Check the injury in late winter and trim away any dead wood.
Check the section of trunk below the grafted scion and clip off any branches growing below the graft. Do this periodically through the growing season, The junction between the rootstock and the scion always presents more resistance to sap flow than does normal wood. Any branch growing below the junction could outgrow the valuable part of the tree. Only the grafted section bears high-quality fruit.