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; 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 kelloggii, the California black oak or 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 alba, the white oak, is one of the preeminent hardwoods of eastern and central North America. It is a long-lived oak, native to eastern and central North America and found from Minnesota, Ontario, Quebec, and southern Maine south as far as northern Florida and eastern Texas. Specimens have been documented to be over 450 years old.
Quercus robur, the pedunculate 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 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 bicolor, the swamp white oak, is a North American species of medium-sized trees in the beech family. It is a common element of America's north central and northeastern mixed forests. It can survive in a variety of habitats. It forms hybrids with bur oak where they occur together in the wild.
Quercus suber, commonly called the cork oak, is a medium-sized, evergreen oak tree in the section Quercus sect. Cerris. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the cores of cricket balls. It is native to southwest Europe and northwest Africa. In the Mediterranean basin the tree is an ancient species with fossil remnants dating back to the Tertiary period. It can survive for as long as two centuries. Typically, once it reaches 25 years old, its thick bark can be harvested for cork every 9 to 12 years without causing harm to the tree.
Quercus pubescens, commonly known as the downy oak, pubescent oak or Italian oak, is a species of white oak native to southern Europe and southwest Asia. It is found from northern Spain (Pyrenees) and France in the West to Turkey and the Caucasus in the East.
The purple hairstreak is a butterfly in the family Lycaenidae distributed throughout much of Europe, North Africa, Anatolia, Caucasia, and Transcaucasia. The larva feeds on Quercus robur, Quercus petraea, Quercus cerris and Quercus ilex.
Quercus dentata, also called Japanese emperor oak, daimyo oak, or Korean oak, is a species of oak native to East Asia. The name of the tree is often translated as "sweet oak" in English to distinguish it from Western varieties. It is placed in section Quercus.
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.
The woodlands of the Iberian Peninsula are distinct ecosystems on the Iberian Peninsula. Although the various regions are each characterized by distinct vegetation, the borders between these regions are not clearly defined, and there are some similarities across the peninsula.
Andricus quercuscalicis is a gall wasp species inducing knopper galls.
Andricus grossulariae is a gall wasp species inducing agamic acorn cup galls on oak tree acorn cups and sexual phase galls on catkins. Synonyms include Andricus fructuum, Andricus gemellus, Andricus intermedius, Andricus mayri and Cynips panteli.
Lapiș Forest nature reserve IUCN category IV, is located in northwestern Romania, in the west of Sălaj County, near the village of Nușfalău, which is about 9 km from Șimleu Silvaniei.
Polonezköy Nature Park is a nature park in the village of Polonezköy in Istanbul, Turkey.
Quercus serrata, the jolcham oak, is an East Asian species of tree in the beech family. It is native to China, Taiwan, Japan, and Korea.
Quercus hartwissiana, the Strandzha oak, is a species of oak, native to southeastern Bulgaria, northern Asia Minor along the Black Sea, and the Caucasus. It was described by the Finnish-born Russian botanist and entomologist Christian von Steven in 1857.
Andricus infectorius is a species of gall-forming wasp. The species was named by the German biologist Theodor Hartig, in 1843 and is found in Europe.
Orchestes pilosus is a beetle of the family Curculionidae found in Europe. It was first described by Johan Christian Fabricius in 1781. The larvae are leaf miners on oak.
Oak regeneration failure is a woodland phenomenon whereby insufficient oak (Quercus) seedlings and saplings are recruited into the canopy to replace dead mature oaks. The result is a local decline in oak numbers while other more shade-tolerant trees such as maple, lime, and ash may become more prominent. Oak regeneration failure has been observed across Eastern and Midwestern forests in the United States as well as in Europe.
