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ClassificationThe genus is divided into two subgenera and a number of sections:
Missing image Quercus_kerrii_acorns.jpg Acorns of a species in subgenus Cyclobalanopsis
Uses Oaks are hardwood trees, the wood commonly used in furniture and flooring. The bark of Quercus suber, or Cork oak, is used to produce wine stoppers (corks). This species grows in the Mediterranean Sea region, with Portugal, Spain, Algeria and Morocco producing most of the world's supply. Some European and American oak species are used to make barrels where wine and other spirits are aged; the barrels contribute to the taste. Of the North American oaks, the most prized of the red oak group for lumber, all of which is marketed as red oak regardless of the species of origin, is that of the Northern red oak, Quercus rubra (a.k.a. Q. borealis). The standard for the lumber of the white oak group, all of which is marketed as white oak, is the White oak, Quercus alba. White oak is often used for the construction of barrels for aging wine. The wood of Quercus robur, the English oak and Quercus petraea, the Sessile oak, is extensively used in Europe. The bark of the White Oak is dried and used in medical preparations. Oak bark is also rich in tannin, and is used by tanners for tanning leather. Acorns are used for making flour or roasted for acorn coffee. CultivationMissing image Raunkiaer.jpg A Pedunculate oak in Denmark Oak acorns require stratification to stimulate sprouting. Most white oaks need immediate stratification; indeed, species such as the Chestnut oak (Quercus prinus) will sprout a root upon falling and must have a suitable substrate for immediate rooting. On the other hand, many red oak acorns may be stratified for up to two years before sprouting. Diseases and pestsSudden Oak Death (Phytophthora ramorum) is a water mould fungus that can kill oaks within just a few weeks. Oak Wilt, caused by the fungus Ceratocystis fagacearum (a fungus closely related to Dutch Elm Disease), is also a lethal disease of some oaks, particularly the red oaks (the white oaks can be infected but resist the disease better, and are not usually killed). Other dangers include wood-boring beetles, as well as root rot in older trees which may not be apparent on the outside, often only being discovered when the trees come down in a strong gale. The leaves of oak are eaten by the larvae of Lepidoptera species such as Oak Hook-tip, Blotched Emerald and Common Emerald. Cultural significanceThe oak is a common symbol of strength and endurance. The oak is the national tree of the United Kingdom, Germany and the United States. Historical note on Linnaean speciesLinnaeus described only five species of oak from eastern North America, based on general leaf form. These were White oak, Q. alba, Chestnut oak, Q. prinus, Red oak, Q. rubra, Willow oak, Q. phellos, and Water oak, Q. nigra. Because he was dealing with confusing leaf forms, the Q. prinus and Q. rubra specimens actually included mixed foliage of more than one species. For that reason, some taxonomists in the past proposed different names for these two species (Q. montana and Q. borealis, respectively) but the original Linnaean names have now been lectotypified with only the specimens in Linnaeus' herbarium that refer to the species the names are applied to now.   See alsoExternal links
da:Eg (Quercus) de:Eichen eo:Kverko es:Roble [[fr:Ch�ne]] nah:Teocuahuitl nl:Eik ja:オーク pl:Dąb [[pt:Carvalho (�rvore)]] sv:Ekar |
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