Quercus

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Oak

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Quercus - The Oak Tree

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Quercus

Category Tree, Perennial
Kingdom Plantae
Division Magnoliophyta
Class Angiospermae
Order
Family
Species in this genus
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Aden Earth Zone

3 - 15

Cultivation

Characteristics

About

An oak is a Tree or Shrub in the Genus Quercus (; Latin "oak tree"), of which about 600 species exist on earth. "Oak" may also appear in the names of Species in related genera, notably Lithocarpus. The genus is native to the northern hemisphere, and includes Deciduous and Evergreen species extending from cold latitudes to Tropical Asia and the Americas.a Tree or Shrub in the Genus Quercus (; Latin "oak tree"), of which about 600 species exist on earth. "Oak" may also appear in the names of Species in related genera, notably Lithocarpus. The genus is native to the northern hemisphere, and includes Deciduous and Evergreen species extending from cold latitudes to Tropical Asia and the Americas.

 
Oaks have Spirally arranged leaves, with a lobed margin in many species; some have serrated leaves or entire leaves with a smooth margin. The Flowers are Catkins, produced in spring. The Fruit is a nut called an Acorn, borne in a cup-like structure known as a Cupule; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on species. The Live oaks are distinguished for being Evergreen, but are not actually a distinct group and instead are dispersed across the genus.


Popular Cultivated Species

White Oak Quercus alba

Scarlet Oak Quercus coccinea

Pin Oak Quercus palustris

Chiquapin Oak Quercus prinoides

English Oak Quercus robur

Red Oak Quercus rubra


Quercus stellata.jpg
Uses

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Oak wood has a density of about 0.75 g/cm³, great strength and hardness, and is very resistant to insect and fungal attack because of its high Tannin content. It also has very attractive grain markings, particularly when Quartersawn. Wide, quarter-sawn boards of oak have been prized since the Middle Ages for use in interior paneling of prestigious buildings such as the debating chamber of the House of Commons in London, England, and in the construction of fine furniture. Oak wood, from Quercus robur and Quercus petraea, was used in Europe for the construction of Ships, especially naval men of war, until the 19th century, and was the principal timber used in the construction of European timber-framed buildings. Today oak Wood is still commonly used for Furniture making and flooring, timber frame buildings, and for veneer production. Barrels in which red Wines, Sherry, and spirits such as Brandy, Scotch whisky and Bourbon whiskey are aged are made from European and American oak. The use of oak in wine can add many different dimensions to wine based on the type and style of the oak. Oak barrels, which may be charred before use, contribute to the colour, taste, and aroma of the contents, imparting a desirable oaky Vanillin flavour to these drinks. The great dilemma for wine producers is to choose between French and American oakwoods. French oaks (Quercus robur, Q. petraea) give the wine greater refinement and are chosen for best wines since they increase the price compared to those aged in American oak wood. American oak contributes greater texture and resistance to ageing, but produces more violent wine bouquets. Oak wood chips are used for smoking fish, meat, Cheeses and other foods.
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Japanese oak is used in the making of professional drums from manufacturer Yamaha Drums. The higher density of oak gives the drum a brighter and louder tone compared to traditional drum materials such as Maple and Birch.
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. Of the North American oaks, the Northern red oak Quercus rubra is the most prized of the red oak group for lumber, all of which is marketed as red oak regardless of the species of origin. It is not good for outdoor use due to its open capillaries. One can blow air through an end grain piece 10 inches long to make bubbles come out in a glass of water. These openings give fungus easy access when the finish deteriorates. 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 to make Wine barrels. The wood of the Deciduous Pedunculate Oak Quercus robur and Sessile Oak Quercus petraea accounts for most of the European oak production, but evergreen species, such as Holm oak Quercus ilex, and Cork oak Quercus suber also produce valuable timber.
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.
In Korea, oak bark (Goolpy) is used for traditional roof construction.
Acorns are used for making flour or roasted for acorn coffee.
Oak Galls were used for centuries as the main ingredient in manuscript ink, harvested at a specific time of year.





Biodiversity and ecology

Oaks are keystone species in a wide range of habitats from Mediterranean semi-desert to subtropical rainforest. For example, oak trees are important components of hardwood forests, and certain species are particularly known to grow in associations with members of the Ericaceae in Oak-heath forests. A number of kinds of truffles, including the two well known varieties, the black Périgord truffle and the white Piedmont truffle, have symbiotic relationships with oak trees.

btropical rainforest. For example, oak trees are important components of hardwood forests, and certain species are particularly known to grow in associations with members of the Ericaceae in Oak-heath forests. A number of kinds of truffles, including the two well known varieties, the black Périgord truffle and the white Piedmont truffle, have symbiotic relationships with oak trees.
Many species of oaks are under threat of extinction in the wild, largely due to land use changes, livestock grazing and unsustainable harvesting. For example, over the past 200 years, large areas of oak forest in the highlands of Mexico, Central America and the northern Andes have been cleared for coffee plantations and cattle ranching. There is a continuing threat to these forests from exploitation for timber, fuelwood and charcoal . In the USA, entire oak ecosystems have declined due to a combination of factors still imperfectly known, but thought to include fire suppression, increased consumption of acorns by growing mammal populations, herbivory of seedlings, and introduced pests . In a recent survey, 78 wild oak species have been identified as being in danger of extinction, from a global total of over 500 species <ref>Oldfield, S. &amp;amp;amp;amp;amp;amp; Eastwood, A. (2007) The Red List of Oaks Flora &amp;amp;amp;amp;amp;amp; Fauna International (FFI) and Botanic Gardens Conservation International (BGCI) ISBN: 9781 903703 25 0</ref>. The proportion under threat may be much higher in reality, as there is insufficient information about over 300 species, making it is near impossible to form any judgement of their status.

Diseases and pests

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Oak Mildew.JPG
Sudden Oak Death (Phytophthora ramorum) is a Water mould 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 generally live longer). Other dangers include wood-boring Beetles, as well as root Rot in older trees which may not be apparent on the outside, often being discovered only when the trees come down in a strong Gale. Oak apples are Galls on oaks made by the Gall wasp. The female kermes scale causes galls to grow on Kermes oak. Oaks are used as food plants by the Larvae of Lepidoptera (Butterfly and Moth) species such as the Gypsy Moth, Lymantria dispar, which can defoliate oak and other broadleaved tree species in North America.

A considerable number of Galls are found on oak leaves, buds, flowers, roots, etc. Examples are Oak artichoke gall, Oak Marble gall, Oak apple gall, Knopper gall, and Spangle gall.
A number of species of fungus cause Powdery mildew on oak species. In Europe the species Erysiphe alphitoides is the most common cause.
A new and as yet little understood disease of mature oaks, Acute oak decline, has been reported in parts of the UK since 2009.
Additionally, the Oak Processionary Moth (Thaumetopoea processionea) has become a serious threat in the UK since 2006. It defoliates the trees, and is hazardous to human health.

Toxicity

The leaves and acorns of the oak tree are poisonous to Cattle, Horses, Sheep, and Goats in large amounts due to the toxin Tannic acid, and cause kidney damage and Gastroenteritis. Additionally, once livestock have a taste for the leaves and acorns, they may seek them out. Symptoms of poisoning include lack of appetite, depression, constipation, diarrhea (which may contain blood), blood in urine, and colic. The exception to livestock and oak toxicity is the Domestic pig, which may be fed entirely on acorns in the right conditions, and has traditionally been pastured in oak woodlands (such as the Spanish Dehesa and the English system of Pannage) for hundreds of years. Acorns are also edible to humans in processed form, after leaching of the tanins. They are a staple part of the forage consumed by wildlife, including squirrels and jays.


Notes

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Bibliography

External links

Retrieved from "http://www.theplantencyclopedia.org/wiki/Quercus"
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