5. Vaccinium L. (blueberry)

(Vander Kloet, 1988)

Plants shrubs or less commonly small trees, sometimes evergreen, often colonial by stolons and/or rhizomes. Twigs glabrous or hairy, sometimes with small, orangish, warty pustules, the winter buds small, ovoid, with 3 to several outer scales, these usually glabrous. Leaves well spaced along the branches, sessile or short-petiolate. Leaf blades herbaceous to thick and leathery, the margins entire or finely and inconspicuously toothed, often also minutely hairy, the upper surface glabrous at maturity, the undersurface glabrous or inconspicuously hairy, lacking yellow resin glands (a few glands rarely present in V. corymbosum). Inflorescences mostly axillary, loose clusters or short racemes, less commonly reduced to solitary flowers, the flowers sometimes subtended by small, leaflike bracts at the base of the stalk, sometimes also with minute, scalelike bractlets toward the stalk midpoint. Flowers actinomorphic, epigynous. Hypanthium fused to the ovary, glabrous, usually somewhat glaucous, lacking yellow resin glands. Calyces deeply (4)5-lobed, glabrous, sometimes glaucous, the lobes triangular to broadly triangular, usually persistent at fruiting. Corollas tubular to urn-shaped or bell-shaped, (4)5-lobed, white or greenish white, often pinkish-tinged, the lobes ascending to recurved. Stamens (8)10, not exserted (except in V. stamineum), the filaments short, straight, attached at the corolla base, with or without spurs near the anther-filament junction, the anther sacs tapered into slender tubes toward the apparent tip, dehiscing by an oblique, terminal pore. Ovary inferior, with usually 5 locules, the placentation axile. Styles slender, at least slightly exserted, the stigma capitate, occasionally slightly lobed. Ovules numerous. Fruits berries, with 5 to numerous seeds. Seeds 0.8–2.0 mm long, asymmetrically ovate in outline, somewhat flattened and usually somewhat angular, the surface finely honeycombed with a network of minute, angular pits, orangish brown. About 400 species, North America to South America, Europe, Africa, Madagascar, Asia to Malesia.

Vaccinium is found in many parts of the world, usually on acidic, sandy, or peaty soils. The berries are an important food source for many species of birds, squirrels, and bears. Deer and rabbits browse on the young twigs and leaves. The genus is commercially important for its berries, including blueberries, cranberries, cowberries, lingonberries, and bilberries, which are eaten raw or cooked and are variously prepared into jams, pies, and juices. In North America, several species of blueberries have been improved by plant breeders and are cultivated commercially, mostly in the northern and northeastern United States and Canada. These include V. corymbosum (highbush blueberry), V. macrocarpon Aiton (cranberry), and V. angustifolium Aiton (sweet lowbush blueberry). Many other species of blueberry are harvested from the wild, including V. pallidum in Missouri. Some species, such as V. stamineum, are generally considered unpalatable, but individual plants may yield good fruit.

The flowers of Vaccinium species are visited by large numbers of bees, primarily species of bumblebees and andrenids, but also honeybees. Pollinators receive both nectar (from a disk inside the base of the corolla) and pollen as their reward. The flowers are usually pendant, with the nectar held in place by the filaments. Flowers are usually protandrous; that is, the stamens mature first, with the styles maturing later, a mechanism to promote cross-pollination. Pollen accumulated in the long, narrow tubes falls out or is “buzzed out” when these are disturbed by an insect visitor (Crane et al., 1985). The stigmas become receptive after the pollen is dispersed.