Blueberries are flowering plants of the genus Vaccinium (a genus which also includes cranberries and bilberries) with dark-blue berries and are perennial. Species in the section Cyanococcus are the most common fruits sold as "blueberries" and are native to North America (commercially cultivated highbush blueberries were not introduced into Europe until the 1930s).
They are usually erect but sometimes prostrate shrubs varying in size from 10 centimeters (3.9 in) to 4 meters (160 in) tall. In commercial blueberry production, smaller species are known as "lowbush blueberries" (synonymous with "wild"), and the larger species are known as "highbush blueberries".
The leaves can be either deciduous or evergreen, ovate to lanceolate, and 1–8 cm (0.39–3.1 in) long and 0.5–3.5 cm (0.20–1.4 in) broad. The flowers are bell-shaped, white, pale pink or red, sometimes tinged greenish. The fruit is a berry 5–16 millimeters (0.20–0.63 in) diameter with a flared crown at the end; they are pale greenish at first, then reddish-purple, and finally dark blue when ripe. They have a sweet taste when mature, with variable acidity. Blueberry bushes typically bear fruit in the middle of the growing season: fruiting times are affected by local conditions such as altitude and latitude, so the height of the crop can vary from May to August depending upon these conditions.