Plant: Vigorous tree with strong apical control with an erect-pyrimidal canopy shape; grows to 18m (> 50 ft). In cultivation, sweet cherries are maintained <4m (12 ft) in height. Leaves are relatively large, elliptic with acute tips, petioled, and strongly veined.
Flowers: White, with long pedicels, borne in racemose clusters of 2-5 flowers on short spurs with multiple buds at tips; the distal bud is vegetative and continues spur growth. Spurs are long-lived, producing for 10-12 years. Bloom occurs relatively late in spring, so frost is less of a hazard than for other stone fruits, except sour cherries, which bloom slightly later.
Pollination: Pollination is absolutely essential for production, since sweet cherries are self-incompatible. 25-50% of flowers must set fruit for a commercial crop. Bees are the main pollinator. Pollinizers are usually set every third tree in every third row, or in alternate rows.
Fruit: A drupe; small 0.5-1 inch diameter, glabrous, with long pedicel attached. Fruit color ranges from pale yellow to dark purple (black).
Thinning is unnecessary for fruit size development, and since a high proportion of flowers must set for a crop, this is not practiced.
Maximum yields are obtained beginning in the 5-6th year after budding, and trees are productive for 25-30 years, despite living much longer.
Plant: Medium sized tree with a rounder, more spreading habit than the erect sweet cherry. Kept <4m (12 ft) in cultivation. Leaves elliptic with acute tips, smaller than sweet cherry, petioled.
Flower: Similar to sweet cherry. Sour cherry inflorescence buds usually produce 2-4 flowers, with long pedicels, as in sweet cherry. However, 35-45% of the flowers are borne laterally on 1-yr wood, not exclusively on spurs as in sweets. Spurs are shorter-lived on sour than sweet, gradually declining in productivity over 3-5 years.
Sour cherries are the latest blooming of the stone fruits, therefore would be less frost prone than sweets. However, frost is still a major limitation to sour cherry production in the eastern US.
Pollination: Sour cherries are self-fertile, and require no pollinizers.
Fruit: Fruits are the same as for sweet cherry, but sour cherries generally have lower sugars and higher organic acid contents, and are generally red in color.
Fruiting begins earlier for sour cherry trees, after 3-4 yr. Productive life is shorter, however, only 20-25 yr.
Thinning is unnecessary for sours since a high proportion must set for a full crop.