Plums are a sweet fruit used for jams and jellies, freezing, canning and eating fresh from the tree. Plum trees are self-unfruitful, except for a few, which are self-fruitful, and require that a suitable pollinator be planted nearby. Four types of plums are grown -- Japanese, Damson, and European -- which usually produce fruit three to five years after planting; the other type is the American plum.
Italian and Green Gage are European-type plum varieties. Green Gage is an oval plum that has amber flesh and greenish-yellow skin. Italian is an oval plum that has yellowish flesh and purple-blackish skin. When the flesh of the Italian is cooked, it turns red. Most European-type plum trees are self-fruitful, but to increase the fruit productions, trees should be pollinated with another cultivar from the European type and not from Japanese or Damson types. Cultivars must be planted within 50 to 100 feet from each other.
French Damson and Shropshire belong to the Damson-type plums, which are very small plums with a tart taste. Damson plums are rarely eaten fresh from the tree but are used for canning, jellies, jams and pies. Shropshire and French Damson plums have round bluish skins with yellowish-greenish flesh. The plum tree is self-fruitful, but is more productive with cross-pollination from another cultivar, such as the French Damson. Both varieties ripen on the tree in late August.
Elephant Heart, Kelsey and Nubiana are Japanese type plums. Elephant Heart plums are heart-shaped with a reddish-purple skin when the fruit is ripe. Kelsey plums have greenish-yellowish flesh and skin, while the Nubiana plums are oblong and have yellow flesh and purplish-black skin. Japanese-type plum trees must be pollinated with a cultivar from the Japanese type and not from Damson or European types. Cultivars must be within 50 to 100 feet from each other for cross pollination.
American plums grow throughout the central and eastern U.S. In Ohio, American plum trees grow in the wild, according to the Ohio Department of Natural Resources. Plums are ready for harvest when the fruit is a bright red, which may have a slight yellowish hue. White flowers appear in early spring before the foliage appears. American plums are oblong with reddish or yellowish skins and golden flesh. Plums are good for jams and jellies because of the high acid and pectin content.