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 in a cup. The genus is widely distributed in the Northern Hemisphere; it includes some 500 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.
Quercus robur, the pedunculate oak, is a species of flowering plant in the beech and oak family, Fagaceae. It is a large tree, native to most of Europe and western Asia, and is widely cultivated in other temperate regions. It grows on soils of near neutral acidity in the lowlands and is notable for its value to natural ecosystems, supporting a very wide diversity of herbivorous insects and other pests, predators and pathogens.
Quercus ilex, the evergreen oak, holly oak or holm oak is a large evergreen oak native to the Mediterranean region. It is a member of the Ilex section of the genus, with acorns that mature in a single summer.
Quercus petraea, commonly known as the sessile oak, Cornish oak, Irish Oak or durmast oak, is a species of oak tree native to most of Europe and into Anatolia and Iran. The sessile oak is the national tree of Ireland, and an unofficial emblem in Wales and Cornwall.
An oak savanna is a type of savanna—or lightly forested grassland—where oaks are the dominant trees. The terms "oakery" or "woodlands" are also used commonly, though the former is more prevalent when referencing the Mediterranean area. These savannas were maintained historically through wildfires set by lightning, humans, grazing, low precipitation, and/or poor soil.
Quercus falcata, also called southern red oak, spanish oak, bottomland red oak or three-lobed red oak is an oak. Native to the southeastern United States, it gets its name the "Spanish Oak" as these are the areas of early Spanish colonies, whilst "southern red oak" comes from both its range and leaf color during late summer and fall. The southern red oak is a deciduous angiosperm, so has leaves that die after each growing period and come back in the next period of growth.
Quercus rotundifolia, the holm oak or ballota oak, is an evergreen oak native to the western Mediterranean region, with the majority on the Iberian Peninsula and minor populations in Northwest Africa. The species was first described by Jean-Baptiste Lamarck in 1785. It is the typical species of the Iberian dehesa or montado, where its sweet-astringent acorns are a source of food for livestock, particularly the Iberian pig. Its acorns have been used for human nourishment since the Neolithic era. It is placed in section Ilex. Some authors described it as a subspecies of Quercus ilex.
Quercus sagrana, also spelt Quercus sagraeana, the Cuban oak, is a medium-sized evergreen tree native to western Cuba in the Cuban pine forests ecoregion. It is the only oak native to the Caribbean.
Quercus delgadoana is an endangered species of oak in the family Fagaceae, found in eastern Mexico. It was originally misidentified as other members of the genus Quercus, but was determined as a new species in 2011.
Quercus welshii, the wavy leaf oak, shinnery oak, or Tucker oak, is a North American species of shrub in the found in the Colorado Plateau and Canyonlands region of the southwestern United States.
Quercus phillyreoides is a species of flowering plant in the genus Quercus, placed in subgenus Cerris and section Ilex. It is evergreen, withstands frost and can be grown in hardiness zone 7. It is native to southern China, the Ryukyu Islands, and Japan, and has been introduced to Korea.
Quercus margarettae, the sand post oak or dwarf post oak, is a North American species of oak in the beech family. It is native to the southeastern and south-central United States from Virginia to Florida and west as far as Texas and Oklahoma. There are historical reports of the species growing in New York State, but it has not been seen there in years.
Quercus vulcanica is a species of flowering plant in the Fagaceae family. It is referred to by the common name Kasnak oak, and is a rare species of tree native to Lebanon, Syria, and Turkey. It is placed in section Quercus.
Jeannine Cavender-Bares is a Distinguished McKnight University Professor at the University of Minnesota in the Department of Ecology, Evolution & Behavior. Her research integrates evolutionary biology, ecology, and physiology by studying the functional traits of plants, with a particular focus on oaks.
Quercus lineata is a species of Quercus (oak) in the beech family Fagaceae, belonging to subgenus Cerris, section Cyclobalanopsis. It was first described by Carl Ludwig von Blume.
Quercus sideroxyla, called the Santa Rosa oak and encino colorado, is a species of oak native to northern and southwestern Mexico. Used for charcoal production, it prefers to grow at elevations from 1,800 to 2,700 metres. It is placed in section Lobatae.
Quercus × bimundorum, known as two worlds oak, is a naturally occurring hybrid of white oak, Quercus alba, and pedunculate oak, Quercus robur. It occurs sporadically where they come in contact in the United States. Its parents are both placed in Quercus sect. Quercus.
Quercus saltillensis is a species of oak. It is native to northeastern Mexico. It is placed in Quercus section Lobatae.
Quercus subgenus Cerris is one of the two subgenera into which the genus Quercus was divided in a 2017 classification. It contains about 140 species divided among three sections. It may be called the Old World clade or the mid-latitude clade; all species are native to Eurasia and North Africa.
