An oak is a tree or shrub in the genus Quercus of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably Lithocarpus, as well as in those of unrelated species such as Grevillea robusta and the Casuarinaceae (she-oaks). 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. 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 second greatest area of oak diversity is China, with approximately 100 species.
Quercus kelloggii, the California black oak, also known as Kellogg oak, is an oak in the red oak section, native to western North America. Although genetically separated from them for more than 20 million years, its leaves are remarkably similar in appearance to several other members of the red oak section including the red oak and the black oak found in eastern and central North America.
Quercus rubra, the northern red oak, is an oak tree in the red oak group. It is a native of North America, in the eastern and central United States and southeast and south-central Canada. It has been introduced to small areas in Western Europe, where it can frequently be seen cultivated in gardens and parks. It prefers good soil that is slightly acidic. Often simply called red oak, northern red oak is so named to distinguish it from southern red oak (Q. falcata), also known as the Spanish oak. Northern Red Oak is sometimes called champion oak.
Quercus muehlenbergii, the chinquapinoak, is a deciduous species of tree in the white oak group. The species was often called Quercus acuminata in older literature. Quercus muehlenbergii is native to eastern and central North America. It ranges from Vermont to Minnesota, south to the Florida panhandle, and west to New Mexico in the United States. In Canada it is only found in southern Ontario, and in Mexico it ranges from Coahuila south to Hidalgo.
Quercus robur, commonly known as common oak, pedunculate oak, European oak or English oak, is a species of flowering plant in the beech and oak family, Fagaceae. It is a large tree, native to most of Europe west of the Caucasus. It is widely cultivated in temperate regions elsewhere and has escaped into the wild in scattered parts of China and North America.
Quercus cerris, the Turkey oak or Austrian oak, is an oak native to south-eastern Europe and Asia Minor. It is the type species of Quercus sect. Cerris, a section of the genus characterised by shoot buds surrounded by soft bristles, bristle-tipped leaf lobes, and acorns that usually mature in 18 months.
Quercus macrocarpa, the bur oak or burr oak, is a species of oak tree native to eastern North America. It is in the white oak section, Quercus sect. Quercus, and is also called mossycup oak, mossycup white oak, blue oak, or scrub oak. The acorns are the largest of any North American oak, and are important food for wildlife.
Quercus douglasii, known as blue oak, is a species of oak endemic to California, common in the Coast Ranges and the foothills of the Sierra Nevada. It is California's most drought-tolerant deciduous oak, and is a dominant species in the blue oak woodland ecosystem. It is occasionally known as mountain oak and iron oak.
Quercus gambelii, with the common name Gambel oak, is a deciduous small tree or large shrub that is widespread in the foothills and lower mountains of western North America. It is also regionally called scrub oak, oak brush, and white oak.
Quercus coccinea, the scarlet oak, is a deciduous tree in the red oak section Lobatae of the genus Quercus, in the family Fagaceae.
Quercus acutissima, the sawtooth oak, is an Asian species of oak native to China, Tibet, Korea, Japan, Indochina and the Himalayas. It is widely planted in many lands and has become naturalized in parts of North America.
Quercus lobata, commonly called the valley oak or roble, grows into the largest of California oaks. It is endemic to California, growing in interior valleys and foothills from Siskiyou County to San Diego County. Mature specimens may attain an age of up to 600 years. This deciduous oak requires year-round access to groundwater.
Quercus lyrata, the overcup oak, is an oak in the white oak group. The common name, overcup oak, refers to its acorns that are mostly enclosed within the acorn cup. It is native to lowland wetlands in the eastern and south-central United States, in all the coastal states from New Jersey to Texas, inland as far as Oklahoma, Missouri, and Illinois. There are historical reports of it growing in Iowa, but the species appears to have been extirpated there. It is a slow-growing tree that often takes 25 to 30 years to mature. It has an estimated lifespan of 400 years.
Oak apple or oak gall is the common name for a large, round, vaguely apple-like gall commonly found on many species of oak. Oak apples range in size from 2 to 4 centimetres in diameter and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae. The adult female wasp lays single eggs in developing leaf buds. The wasp larvae feed on the gall tissue resulting from their secretions, which modify the oak bud into the gall, a structure that protects the developing larvae until they undergo metamorphosis into adults.
Quercus faginea, the Portuguese oak, is a species of oak native to the western Mediterranean region in the Iberian Peninsula. Similar trees in the Atlas Mountains of northwest Africa are usually included in this species, or sometimes treated as a distinct species, Quercus tlemcenensis. It occurs in mountains from sea level to 1,900 metres above sea level, and flourishes in a variety of soils and climates. Out of all the oak forests in the Iberian Peninsula, the southern populations of Portuguese oak were found to have the highest diversity and endemism of spider species.
Quercus nigra, the water oak, is an oak in the red oak group, native to the eastern and south-central United States, found in all the coastal states from New Jersey to Texas, and inland as far as Oklahoma, Kentucky, and southern Missouri. It occurs in lowlands and up to 450 meters in elevation.
Quercus ilicifolia, commonly known as bear oak or scrub oak, is a small shrubby oak native to the eastern United States and southeastern Canada. Its range extends in the United States from Maine to North Carolina, with reports of a few populations north of the international frontier in Ontario. The name ilicifolia means "holly-leaved."
Quercus aliena, the galcham oak or oriental white oak, is a species of oak in the family Fagaceae, in the white oak section Quercus.
Quercus infectoria or the Aleppo oak is a species of oak well known for producing galls that have been traditionally used for centuries in Asia medicinally while also used in softening leather and in making black dye and ink.
Quercus pyrenaica, commonly known as Pyrenean oak, is a tree native to southwestern Europe and northwestern North Africa. Despite its common name, it is rarely found in the Pyrenees Mountains and is more abundant in northern Portugal and north and northwestern Spain.
