Please note: Plums and prunes are quarantined by the Idaho Department of Agriculture to prevent the introduction of diseases. Except for the fruit, no plant parts can be imported into Idaho unless they have been grown in a disease-free area and are accompanied by a phytosanitary certificate. Homeowners should purchase their peach and plum stocks at nurseries in Idaho.
Prunes are simply plums that develop high enough sugar concentrations in the fruit to allow the fruit to be dried without spoiling. The trees grow 10 to 20 feet tall and bear fruit three to five years after planting. Cultivars are budded onto rootstocks.
Both European and Japanese cultivars are available. Nearly all Japanese cultivars require cross pollination, as do many European cultivars. As a general rule, plant two or more cultivars close together. Plums are less hardy than apples. Japanese plums are injured at temperatures between -10 and -15 F. European plums are injured at temperatures between -15 and -20 F. Although adaptable to a wide range of soil conditions, the trees perform best on deep, well drained soil.