seed and takes 6-18 months to mature, depending on the species. The acorns and leaves contain tannic acid, which helps to guard against fungi and insects. There are some 500 extant species of oaks.

Trees in the genus are usually large and slow-growing; Q. alba can reach an age of 600 years, a diameter of 13 ft and a height of 145 ft. The Granit oak in Bulgaria, a Q. robur specimen, has an estimated age of 1,637 years, making it the oldest oak in Europe.