American Plum

Site and soil

American plum fruits best in full sun and will grow and flower at a woodland edge in partial shade with a lighter crop. It is one of the least demanding fruit trees you can plant: well-drained loam is ideal, but it tolerates rocky ground, clay, poor soil and summer drought across a pH from about 5.5 to 7.5. Avoid only the wettest sites. Water needs are low once established.

It suckers from the roots and will form a thicket if you let it, which is how it grows wild. Decide at planting whether you want a thicket, a hedgerow or individual trees, and site it accordingly; a thicket in the middle of a lawn is a mowing problem, while a thicket along a fence line is a wildlife hedge.

Spacing

Mature trees run 15 to 25 ft tall and wide. For a hedgerow or thicket, set them 6 to 10 ft apart and let the suckers fill in. As individual trees, allow 15 to 20 ft and mow or cut the suckers. Keep pollination partners within about 50 ft.

Planting

Plant in early spring while dormant, or in fall after leaf drop.

• Dig the hole as deep as the root system and twice as wide.
• Set the tree with the root flare level with the ground.
• Backfill with native soil and water in well.
• Mulch 3 to 4 inches deep, kept back from the trunk.
• Guard the trunk against rabbits and deer for the first two or three winters.

Pollination

American plum is self-incompatible and needs pollen from a different, unrelated plum. Two seedlings are the minimum and three or more give steadier crops, since seedlings vary in bloom time. The early bloom is worked by honey bees, mason bees and other native bees. American plum will also pollinate the hybrid plums like Toka and Waneta that were bred from it.

First-year care

• Water deeply once a week through the first growing season. After that it manages on rainfall in most years.
• Keep a mulched, grass-free circle around the trunk.
• No fertilizer in year one, and rarely after.
• Remove any fruit that sets in the first year.

Pruning

For a thicket or hedgerow, prune only to remove dead wood and to keep the edge where you want it. For an individual tree, train it to a single trunk with an open center in the first two or three winters, then prune lightly each year in late winter in dry weather, removing dead, crossing and inward wood and cutting suckers at ground level.

Watch for black knot, the hard black swellings on twigs that affect all plums. Cut it out at least 4 inches below the gall in late winter and remove the prunings. Brown rot on ripening fruit is reduced by thinning a heavy set and keeping air moving through the canopy.

Harvest

Seedling trees begin bearing in about 3 to 5 years. Fruit ripens in August into September. A wild plum is ready when the skin has reached full red or yellow, the flesh gives to a gentle press, and the fruit comes off with a light touch; fully ripe fruit often drops, so a sheet under the tree catches the best of it. Underripe wild plums are mouth-puckering; ripe ones are sweet with a tart skin.

The fruit keeps a few days refrigerated. Most of a wild plum crop goes into jam, jelly, sauce, fruit leather or wine, where the skin's tartness is the point. A mature tree or a thicket gives far more than a family uses, and birds, foxes, raccoons and deer take the rest.