Oak

The term oak can be used as part of the common name of any of several hundred species of trees and shrubs in the genus Quercus (from Latin "oak tree"), which are listed in the List of Quercus species, and some 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" (oaks with evergreen leaves) are not a distinct group, instead with their members scattered among the sections below.


Uses
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 quarter-sawn. 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 British 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 until the 19th century, and was the principal timber used in the construction of European timber-framed buildings. Today oakwood is still commonly used for furniture making and flooring, timber frame buildings, and for veneer production. Barrels in which red wines, sherry, brandy and spirits such as 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 color, 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.

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. 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 account 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. 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.

Japanese oak is used in the making of professional drums from manufacturer Yamaha Drums. The rough, hard surface of oak gives the drum a brighter and louder tone compared to traditional drum materials such as maple and birch.


Some species
Quercus robur is commonly known as the pedunculate oak, German oak or English oak. It is native to most of Europe, and to Asia Minor to the Caucasus, and also to parts of North Africa.
Within its native range Q. robur is valued for its importance to insects and other wildlife. Numerous insects live on the leaves, buds, and in the acorns. The acorns form a valuable food resource for several small mammals and some birds, notably Eurasian Jays Garrulus glandarius.
It is planted for forestry, and produces a long-lasting and durable heartwood, much in demand for interior and furniture work. The wood of Q. robur is easily identified just by taking a closer look at the cross-section perpendicular to fibres. The wood is characterised by its distinct (often wide) dark and light brown growth rings. The earlywood displays a vast number of large vessels (~0.5 mm diameter). Rays which resemble of thin (~0.1 mm) yellow or light brown lines run across the growth rings.

Quercus petraea - The Sessile Oak, also known as Durmast Oak, is a species of oak native to most of Europe, and into Anatolia. The wood is important, used for construction purposes, shipbuilding, and for making barrels for wine.

Quercus suber - The Cork Oak (Quercus suber) is a medium-sized, evergreen oak tree in the section Quercus sect. Cerris. It is native to southwest Europe and northwest Africa.
It grows to up to 20 m, although it is typically more stunted in its native environment. The leaves are 4 to 7 cm long, weakly lobed or coarsely toothed, dark green above, paler beneath, with the leaf margins often downcurved. The acorns are 2 to 3 cm long, in a deep cup fringed with elongated scales.
The tree forms a thick, rugged and corky bark. Over time this bark can develop considerable thickness and this can be harvested every 10 to 12 years as cork. The harvesting of cork does not harm the tree and a new layer of cork regrows, making it a renewable resource. The tree is widely cultivated in Spain, Portugal, Algeria, Morocco, France, Italy and Tunisia. Cork Oak forests cover approximately 25,000 square kilometres in those countries. Portugal accounts for 50% of the world cork harvest. Cork Oaks cannot legally be cut down in Portugal, except for forest management felling of old, unproductive trees.
Cork Oaks live about 150 to 250 years. Virgin cork (or 'male' cork) is the first cork cut from generally 25 year old trees. Another 10 to 12 years is required for the second harvest, and a tree can be harvested twelve times in its lifetime. Cork harvesting is done entirely without machinery.
The European cork industry produces 340,000 tonnes of cork a year, with a value of €1.5 billion and employing 30,000 people. Wine corks represent 15% of cork usage by weight but 66% of revenues.

Quercus alba - The tree species Quercus alba, also called "white oak," is one of the pre-eminent hardwoods of eastern North America. It is a long-lived oak in the family Fagaceae, native to eastern North America, from southern Quebec west to eastern Minnesota, and south to northern Florida and eastern Texas. Specimens are known to have lived over 600 years.
Although called the white oak it is very unusual to find an individual with white bark; the usual color is an ashen gray. In the forest it reaches a magnificent height. In the open it develops into a massive broad-topped tree with great limbs striking out at wide angles.

Quercus austrina - The Bluff Oak is an oak species that is native to the southern and western coastal states. It can grow to a height of 45 to 60 feet. Its spread can grow to a width of 35 to 50 feet.

Quercus berberidifolia - It is a native of the scrubby hills of California.

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