![]() ![]() The acorns and leaves contain tannic acid, which helps to guard against fungi and insects. The fruit is a nut called an acorn or oak nut borne in a cup-like structure known as a cupule each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on the species. 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. Many deciduous species are marcescent, not dropping dead leaves until spring. Oaks have spirally arranged leaves, with lobate margins in many species some have serrated leaves or entire leaves with smooth margins. Solitary oak, the Netherlands The leaves of a young oak Pubescent oak tree in four seasons, Zmajevac, Fruška Gora, Serbia Description The second greatest area of oak diversity is China, with approximately 100 species. ![]() North America has the largest number of oak species, with approximately 160 species in Mexico, of which 109 are endemic and about 90 in the United States. The genus Quercus is native to the Northern Hemisphere and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. The common name "oak" also appears in the names of species in related genera, notably Lithocarpus (stone oaks), as well as in those of unrelated species such as Grevillea robusta (silky oaks) and the Casuarinaceae (she-oaks). There are approximately 500 extant species of oaks. Protobalanus (Trelease) O.SchwarzĪn oak is a tree or shrub in the genus Quercus ( / ˈ k w ɜːr k ə s/ Latin "oak tree") of the beech family, Fagaceae. Possible Paleocene & Late Cretaceous records ![]()
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