Pawpaw

Keep water steady for the first two years

Water deeply whenever the top few inches of soil dry out, from planting through the second growing season. Pawpaw wants the equivalent of at least 32 inches of rain a year spread evenly, so make up the gap in any dry stretch rather than waiting for the tree to wilt. Pawpaw comes from moist bottomland soils and transplants carry a fleshy, brittle root system that regenerates slowly, so a young tree cannot mine dry soil for water the way a drought-adapted fruit tree can.

Feed in spring, and stop by midsummer

Once the tree is established, broadcast a balanced granular fertilizer such as 10-10-10 once in spring, from the trunk out to the outermost branches. Do not fertilize after midsummer. Keep soil pH between 5.5 and 6.5, and soil test before adding calcium once the tree starts fruiting. Nitrogen applied late in the season pushes soft new growth that has not hardened off by the first freeze, and pawpaw is fussy about pH: outside roughly 5.5 to 6.5 it cannot take up iron and other micronutrients even when they are present in the soil.

⚠ Avoid fertilizing after midsummer.

Dormant prune to a central leader

While the tree is dormant and still leafless, keep one central trunk with well spaced scaffold branches and remove crossing or rubbing limbs. Spread narrow crotches to widen the angles. Pull root suckers off at the base to hold a single trunk. If a transplant lost a lot of root, cut the top back to match what the roots can still supply. Work in the leafless window before buds begin to swell, which falls later in the north than in the south. Pawpaw wood is weak and its leaves are large and heavy, so narrow crotch angles split under a fruit load. Pruning while dormant also lets you see the framework, and the cuts are made when the tree is not pushing sap.

Hand pollinate between two different trees at bloom

Check the maroon flowers daily through bloom. Take pollen from a flower whose anthers are brown, loose, and shedding yellow dust, and dab it with a small artist's brush onto the stigma of a flower on a genetically different tree while the stigma tips are still green, glossy, and sticky. Two grafted trees of the same cultivar will not work, they are the same plant. Pawpaw flowers are self-incompatible and protogynous, so the stigma is receptive before that same flower's own pollen is ripe. Their natural pollinators are flies and beetles rather than bees, and they visit erratically, which is why a healthy tree covered in bloom so often sets nothing.

Pull webworm nests by hand through summer

Walk the tree through summer looking for Asimina webworm nests, which tie leaves together into a shelter at the shoot tips, and for peduncle borer damage. Prune out and destroy the nests by hand and keep fallen leaves and fruit cleaned up. Trapping, manual removal, and orchard sanitation are the recommended controls. Pawpaw foliage carries its own natural insecticidal compounds, so it has very few serious pests and almost nothing reaches a threshold that a spray would fix. The webworm is the one that concentrates enough to matter, and it is easy to remove while nests are small and few.

⚠ There are no labeled fungicides for pawpaw, and it is a minor crop with very few labeled pesticides of any kind, so do not reach for an orchard spray meant for apple or peach. Bacillus thuringiensis is sometimes used for webworm, but it kills any caterpillar that eats treated leaves, including the zebra swallowtail, whose larvae feed on pawpaw and nothing else. Confirm any product's label lists pawpaw before use.

Shade the tree through its first summer

For any seedling or grafted tree under about 24 inches tall, suspend 33 percent shade cloth above it for the whole establishment year. Remove the shade the following spring once the tree is rooted in and taller. Pawpaw evolved as a forest understory tree, and its seedlings lack the light-shock protection of a sun species: full sun in year one scorches the leaves and stalls or kills a transplant that would otherwise thrive.

Pick by feel and smell, never by color

Start checking when the skin shifts from dark green toward lighter green and yellow, but judge by touch. Pick as soon as flesh softening is first evident: a ripe pawpaw gives when squeezed gently, the way a ripe peach does, gives off a strong fruity aroma, and separates from the stem with a gentle tug. Color alone is unreliable, so squeeze every fruit before you pick it. Fruit picked at first softening finishes ripening indoors within a few days, so do not wait for full softness on the tree. Pawpaw is climacteric, so a fruit that has begun to soften will complete ripening off the tree. A fully immature fruit will not, and no ethylene treatment rescues it. Once softening starts the fruit is too soft to handle within three to five days, which is why feel beats any calendar date.

⚠ Underripe pawpaws can cause gastrointestinal distress. The seeds and bark contain acetogenins and are toxic; do not eat the seeds, and do not eat the skin.

Refrigerate the same day you pick

Get fruit into a refrigerator at 32 to 40 degrees F and 90 to 95 percent humidity as soon as possible after picking. Expect only a few days at room temperature and a few weeks refrigerated. For longer keeping, scoop the pulp, discard the seeds, and freeze the pulp. Pawpaw has a thin skin, no wax layer, and soft custard flesh that bruises on contact, and it keeps respiring hard after picking. Cold slows that metabolism, which is the only thing standing between a ripe pawpaw and fermentation.

⚠ Cold storage is limited to about four weeks even at correct temperature: past roughly four weeks refrigerated, pawpaw loses the capacity to ripen and develops chilling injury, showing as internal black discoloration and off-flavors. Do not try to stretch storage by freezing whole fruit; freeze scooped pulp instead.