oak

Oak refers to any of about 600 species of trees and shrubs in the genus Quercus, within the beech family Fagaceae. Oaks are native to the temperate regions of the Northern Hemisphere, with the greatest diversity in Eurasia and North America. They are commonly divided into two large groups, the white oaks (section Quercus) and the red oaks (section Lobatae in the Americas; other classifications place red oaks in Lobatae). Some species are evergreen, notably the cork oak (Quercus suber) and several Mediterranean oaks such as Quercus ilex.

Leaves vary widely; many oaks have lobed leaves with rounded or pointed lobes, though some are unlobed or finely divided. Oaks produce acorns, the fruit that ripens in one or two years depending on species. Acorn production, or mast, occurs in cycles and can vary from year to year, with some years yielding large crops.

Ecology and biology: Oaks form ectomycorrhizal associations, supporting nutrient uptake and soil communities. They sustain diverse fauna: insects, birds, and mammals rely on oak woodlands for food and habitat. Their long lifespan and structural features also influence forest dynamics and succession.

Uses: Timber is valued for strength and durability, used in furniture, flooring, and cooperage. The cork oak yields commercial cork. Acorns have historically been consumed by humans after tannin removal and are still used in some cuisines.

Threats and conservation: Threats include diseases such as oak wilt (Bretziella fagacearum) and sudden oak death (Phytophthora ramorum), invasive pests, drought, and habitat loss. Conservation emphasizes habitat protection, disease management, and restoration of oak woodlands.