linguistic:paraphrasing
Description

Oaks are hardwood (dicotyledonous) trees, deciduous or evergreen, with spirally arranged leaves, often with lobate margins; some have serrated leaves or entire leaves with smooth margins. Many deciduous species are marcescent, not dropping dead leaves until spring. In spring, a single oak tree produces both staminate ('male') flowers in the form of catkins, and small pistillate ('female') flowers, meaning that the trees are monoecious. The fruit is a nut called an acorn, borne in a cup-like structure known as a cupule; each acorn usually contains one 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 often large and slow-growing; Q. alba can reach an age of 600 years, a diameter of 13 feet (4.0 m) and a height of 145 feet (44 m). The Granit oak in Bulgaria, a Q. robur specimen, has an estimated age of 1637 years, making it the oldest oak in Europe. The Wi'aaSal tree, a live oak in the reservation of the Pechanga Band of Indians, California, is at least 1000 years old, and might be as much as 2000 years old, which would make it the oldest oak in the US. Among the smallest oaks is Q. acuta, the Japanese evergreen oak. It forms a bush or small tree to a height of some 30 feet (9.1 m).