An oak is a hardwood tree or shrub in the genus Quercus of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisphere, with some 475 species, both deciduous and evergreen. Fossil oaks date back to the Middle Eocene. Molecular phylogeny shows that the genus is divided into Old World and New World clades, but many oak species hybridise freely, making the genus's history difficult to resolve.
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622 species Catalogue of Life COL26.10 · CC BY
Shares counted over species below this taxon. Tree of Life v3d, counted live
Not assessed by the IUCN Red List (or no assessment linked via Wikidata).
Dataset v3d. Classification: Catalogue of Life COL26.10 (CC BY 4.0) and Open Tree of Life (CC0). Each photo is credited where it is shown.