Like most other temperate fruit, plums need to be winter-chilled in order to bear. Growing plums is feasible in just about any part of the United States where winter temperatures fall below 40°F. for a few weeks but not below—25°F. for the same period of time.
As usual, select a locally adapted variety, bearing in mind that prune plums will be needed if you want to make a lot of prunes. Regular plums can be dried too, but they have to be pitted and halved . . . their sugar content is not high enough to preserve them without fermentation.
Plums Tree Stock
You will need at least two varieties, since most plums are self-sterile. All plums are root-grafted, which means on a one-year-old tree you'll be getting solid two- or three-year-old rootstock. Plant in fall if the winters in your area are mild enough so that temperatures do not go below the teens except on very rare occasions. Spring planting is fine as long as the tree is completely dormant, but fall planting is better where possible.
Space the trees fifteen to thirty feet apart, depending on the mature size of your particular species. Plum bark is sensitive to sun-scald (to a tree what a sunburn is to people), so wrap a couple of layers of burlap around the lower part of the trunk. Cut the wood back by 25 percent when you plant.
Pruning Plum Trees
Pruning is mostly confined to shaping a wide, open, spreading tree, and, of course, regular maintenance trimming. Once fruiting begins, you may have to support some of the bearing branches like those of your peach trees. Eliminating overbearing by selectively removing small, unripe fruit will also be necessary. Keep all pruning cuts clean and, if possible, seal them over with pitch to protect against heart rot.
Problems and Solutions
As with cherries, birds can be a menace. Try a mulberry hedge around your orchard. Birds simply love mulberries, and they will often stop at the hedge and fill themselves up before they ever reach your fruit.
Harvest plums when fully ripe for eating, just a little before for canning. Prune varieties should be allowed to ripen till they drop . . . into a cheesecloth trampoline you have suspended beneath the tree. Remove fallen fruit daily and sun-dry on screen trays, turning occasionally. If it's rainy, oven-dry in single layers for six hours at 110° F.