oaks

Oaks are trees and shrubs in the genus Quercus, part of the beech family Fagaceae. The genus contains about 600 species native to the temperate regions of the Northern Hemisphere, with a wide distribution in North America, Europe, and Asia, and in parts of the Mediterranean and subtropical regions. Oaks vary from small trees to tall forest trees, with some species evergreen and others deciduous. Most have lobed or toothed leaves and stout trunks with rugged bark. A defining feature is the fruit, the acorn, which develops from the single ovary of the flower and matures in one or two growing seasons. Acorns are a food source for many mammals and birds and support a wide ecological community.

Oaks are important ecologically and economically. They form mixed forests, host numerous invertebrates, and their wood is valued for timber, furniture, and cooperage. They can live for centuries, with some specimens among the longest-lived trees. Growth rates vary; many species are slow-growing but long-lived.

Taxonomy generally divides oaks into several groups, notably the white oaks (section Quercus) and the red oaks (section Lobatae or other regional classifications). White oaks tend to have lighter, sweeter-tasting acorns that mature in one year; red oaks produce tannin-rich, bitter acorns that require two years to mature.

Conservation concerns include habitat loss and diseases such as sudden oak death caused by Phytophthora ramorum, and oak wilt in some regions. Hybridization among oaks is common, contributing to a complex and diverse genus.