Identifying a flowering plum shrub is complex due to a confusion of common names and the distinction between what is a tree and what is a tree. The deciduous purple-leaf sand cherry (Prunus x cistena), also commonly called the cistena plum, can be said to be a shrub or small tree. It will grow in U.S. Department of Agriculture plant hardiness zones 2 through 8.
Origins and Name
Although it is more frequently listed as a purple-leaf sand cherry, P. cisena can be listed as the cistena plum. The frequent name confusion is because both plums and cherries belong to the Prunus genus. In 1910, Dr. N. E. Hansen of South Dakota State University successfully crossed the purple leaf plum (P. cerasifera), indigenous to western Asia, and the indigenous American western sand cherry (P. pumila). To present his plumb-cherry hybrid a botanical name, Hansen combined prunus using cestina, the Sioux word for baby. In answer to the inquiry of whether P. cistena is just a flowering plum or a flowering cherry, then it is a hybrid, half and half.
There is no scientific definition that separates shrubs from trees. 1 useful distinction is that a tree is 13 feet tall and contains a back at least 3 inches wide measured 4 1/2 feet from the floor and also has a definite layer of foliage. Shrubs usually are less than 13 feet tall and have multiple transitions less than 3 inches in diameter. Cistena plum grows 6 to 10 feet tall with a spread of 5 to 8 feet, a shrublike height, although it only has a single trunk, suggesting a tree. In these instances plants are generally recorded as a shrub or small tree.
The slow-growing cistena plum requires little upkeep. It has a curved shape with purple-red leaf which turns red in the autumn. After its leaves appear in the spring, the cistena plum yields fragrant, 1/2-inch-wide white flowers tinged with pink. It later produces scattered 3/4-inch-wide fruits that are utilized to make jellies, pies and jams and are much loved by birds.
Although the cisena plum thrives in full sun, it can be grown in partial shade. Both its blossom and leaf have a richer color if it is grown in the entire sun. It will grow in a wide variety of soils which range from light, sandy soils to heavy clays, although they should be well drained. It will tolerate urban growing conditions. The cistena plum is most usefully grown in a raised planter or at regions where it will prosper as a tree. It is usefully planted as part of a hillside mass of shrubs or as little hedge.
Cistena plums are prone to numerous diseases and insect pests, with the result that they frequently do not live longer than ten years. Japanese beetles such as their leaf and boring insects attack their trunks. Other issue insects include aphids, caterpillars, leafhoppers, scale, spider mites and tent caterpillars. Diseases include dieback, fireblight, honey fungus, leaf curl, leaf spot, powdery mildew and root decay.