Plum trees (Prunus) are perennial trees that belong to the Rosaceae genus, which also contains cherry, apricot and peach trees. Plum trees can belong to one of three groups: European, Japanese or Damson. Damson trees bear tart, reddish-purple plums, while the European and Japanese varieties bear sweet, mild plum fruits.
Plum trees vary in height from 8 feet to 35 feet. Most plum tree species have a spread ranging from 10 to 20 feet in width.
Plum tree bloom delicate, white flowers in clusters of two or three. Japanese plum trees have a tougher bark than the other types of plum trees.
Plum trees are highly susceptible to plum pox, black knot disease, botrytis blight and powdery mildew.
Black knot disease causes black knots to form on twigs, while botrytis blight causes the formation of grayish-silver spore masses. Powdery mildew often looks like a grayish-white film of dust on the leaves.
European plums grow well in the northern regions of the United States (US), while the Japanese varieties fare better in the warmer southern states. The Damson plum tree varieties thrive in USDA hardiness zones 5 to 7.
Many plum tree diseases are caused by excess moisture, so plum trees need to be planted in a location with good drainage. Organic mulches, such as wood chips or sawdust, can help control moisture levels around the plum tree.