Oak

Oak, common name for a large genus of hardwood trees that are widespread in the North Temperate Zone. The oak genus contains about 450 species. Oaks are distinguished from the other ten or so genera in the beech family, to which the oak genus belongs, by various technical characteristics of their minute, clustered flowers, but they are easily recognized by their distinctive fruit, the acorn. The related tan oak, one species of which occurs in the coastal ranges of California and Oregon, also produces an acorn. The tan oak differs from the oak genus in its upright rather than hanging male flower clusters.

About 60 species of oak occur in the United States and Canada, with about 150 additional species in Mexico. They grow in a variety of habitats, from seacoasts to high mountain slopes and from wet lowlands to high, dry mesas. Flowering occurs in the spring, before the new leaves appear, and large quantities of pollen are shed into the wind. The trees may be deciduous (losing their leaves in the fall) or evergreen. Most eastern United States species are deciduous—the live oak of the southeastern coastal plain being a notable exception—whereas the western United States has both many evergreen and many deciduous species.

Oaks produce durable, tough wood and are important lumber trees. The wood is used in cabinetry and barrel making and as flooring and veneers. Corks are made from the thick, spongy bark of the cork oak, which occurs in the Mediterranean region. Several species yield tannins, which are used in the leather-tanning industry, and others yield dyes from their bark. Oaks are of some horticultural importance, but because most are slow growing, they are more often planted in public parks and gardens than in private lawns. Scarlet oak, willow oak, and pin oak, however, are moderate to fast-growing species that are well suited to both purposes.

Scientific classification: Oaks make up the genus Quercus of the family Fagaceae. The tan oak is classified in the genus Lithocarpus. The live oak is classified as Quercus virginiana, the cork oak as Quercus suber, the scarlet oak as Quercus coccinea, the willow oak as Quercus phellos, and the pin oak as Quercus palustris.