Oaks are deciduous or evergreen trees or, rarely, shrubs, of the genus Quercus in the beech family, Fageceae. They are the most important and widespread hardwood trees in the northern temperate region, occurring throughout North America and Eurasia and in Higher elevations extending south into northwestern South America, Cuba, North Africa, and Indonesia. Of the approximately 450 species of oaks, 60 or more, some shrublike in form, are native to the United States and Canada. Oaks dominate the central and southern hardwood forests of the United States, and about 20 species in the eastern United States are commercially important.
Oak furnish more native timber annually then any other broad leaved tree and in total lumber production are second only to the conifers. Oak lumber is used for flooring and wood trim in home construction and for railroad ties, barrels, boats, furnitures, and fuel, including charcoal.
Other oak products include cork, which is produced primarily from the bark of the European cork oak, Q.suber, tannin, a substance used in making leather, from the bark of such trees as the daimyo oak, Q. dentata, of the Orient, dyes, such as quercitron, which is derived from the bark of the black oak, Q. velutine, formerly, inks and dyes from oak galls, formd by oaks around developing gall-wasp larvae; and acorns, which are fed to hogs, used as human food if of the sweet variety, or, if from the valonia oak, Q. macrolepis, used as a source of tannin.