cork oak, name for an evergreen species of the oak genus ( Quercus ) of the family Fagaceae (beech family). The cork oak ( Q. suber ) is native to the Mediterranean region, where most of the world's commercial supply of cork is obtained. It is cultivated elsewhere as an ornamental and has been introduced into warmer regions of the United States because of its economic value. The bark of the tree is stripped off (about every 10 years) and then processed for shipment as commercial cork. There is a cork layer in all trees but it is not as extensive or valuable as in the cork oak. Cork oak is classified in the division Magnoliophyta, class Magnoliopsida, order Fagales, family Fagaceae.