sudden oak death: see diseases of plants; water mold.

poison oak: see poison ivy.

oak, any tree or shrub of the genus Quercus of the family Fagaceae (beech family). This complex genus includes as many as 600, found chiefly in north temperate zones and also in Polynesia. The more southerly species, ranging into the tropics, are usually evergreen. Oaks are cultivated for ornament and are prized as the major source of hardwood lumber. The wood is durable, tough, and attractively grained; it is especially valued in shipbuilding and construction and for flooring, furniture, railroad ties, barrels, tool handles, and veneer (particularly highly burled oak). The oaks are commonly divided into two groups, the black (or red) and the white. The former (e.g., the scarlet, pin, Spanish, willow, laurel, and shingle oaks) are characterized by leaves with sharp-tipped lobes and by acorns that mature in two years. The white oaks (e.g., the white, post, bur, cork, and holly oaks) are characterized by smooth-lobed leaves and acorns that mature in one year. Q. alba, the white oak, is the most important timber tree of the oak genus. Lumber-yielding species of chestnut (genus Castanea) are included in the white oak group when the term is used as a timber classification. The live oaks, evergreen species common in the S and SW United States, are sometimes considered a separate group. The bark of some oaks has been employed in medicine, in tanning, and for dyes; that of the cork oak supplies the cork of commerce. The galls caused by certain insects are utilized commercially. The Mediterranean kermes oak (Q. coccifera) is host to the kermes insect, source of the world's oldest dyestuff. Acorns, the fruit of oak trees, have long been employed as a source of hog feed, tannin (chiefly from valonia, the acorn cup of the Turkish oak, Q. aegilops), oil, and especially food. Acorns were one of the most important foods of the North American forest Native Americans; they were pulverized, leached to extract the bitter taste, and then cooked in various ways. Acorns have also been used as food in other regions where they are native. A symbol of strength, the oak has been revered for both historical and mythological associations. It was the favorite of Jove and Thor and especially sacred to the druids. St. Louis administered justice under an oak, and the Charter Oak is legendary in America. Several unrelated plants are also called oak, e.g., the Jerusalem oak (a lobe-leaved annual of the goosefoot family) and the poison oak of the sumac family (see poison ivy). Oaks are classified in the division Magnoliophyta, class Magnoliopsida, order Fagales, family Fagaceae.

live oak: see oak.

cork oak, name for an evergreen species of the oak genus (Quercus) of the family Fagaceae (beech family). The cork oak (Q. suber) is native to the Mediterranean region, where most of the world's commercial supply of cork is obtained. It is cultivated elsewhere as an ornamental and has been introduced into warmer regions of the United States because of its economic value. The bark of the tree is stripped off (about every 10 years) and then processed for shipment as commercial cork. There is a cork layer in all trees but it is not as extensive or valuable as in the cork oak. Cork oak is classified in the division Magnoliophyta, class Magnoliopsida, order Fagales, family Fagaceae.

White Oak, uninc. community (1990 pop. 18,671), Montgomery and Prince Georges counties, central Md., in the suburbs of Washington, D.C. The site of the former Naval Ordnance Laboratory was renamed the Federal Research Center and is now occupied by the Food and Drug Administration.

Royal Oak, residential city (1990 pop. 65,410), Oakland co., SE Mich., a suburb of Detroit; settled c.1820, inc. as a city 1921. There is metal forging and the manufacture of automotive and computer parts. Royal Oak's population decreased considerably in the late 20th cent. The Detroit Zoological Park is there.

Oak Ridge, city (1990 pop. 27,310), Anderson and Roane counties, E Tenn., on Black Oak Ridge and the Clinch River; founded by the U.S. government 1942, inc. as an independent city 1959. For years Oak Ridge was used by the federal government to pursue activities in the fields of atomic energy and nuclear physics. The site was chosen (1942) for what was called the Clinton Engineer Works, and the city was built to house the workers who developed the uranium-235 and plutonium-239 for the atomic bomb. The community's existence was kept secret from most of the country until the summer of 1945. The project was under the control of the Atomic Energy Commission, but the city has since (1955-59) been turned over to its residents. The former Clinton National Laboratory for nuclear research became (1948) the Oak Ridge National Laboratory. In the 1990s the federal government began decontaminating and leasing much of the complex to private industry, and one section was renamed the East Tennessee Technology Park. The Oak Ridge Associated Universities, a consortium of many educational institutions, manages the Oak Ridge Institute for Science and Education. Tourist attractions include the American Museum of Atomic Energy, a nearby nuclear graphite reactor, and an arboretum.

Oak Park. 1 Village (1990 pop. 53,648), Cook co., NE Ill., a residential suburb adjacent to Chicago; settled 1833, inc. 1901. Some 25 houses there and the Unity Temple (1908) were designed by Frank Lloyd Wright, who lived in the village (1889-1909). Wright's home and studio complex (1889-1911) is now a museum. Ernest Hemingway was born in Oak Park.

2 City (1990 pop. 30,462), Oakland co., SE Mich., a suburb of Detroit; inc. 1927. It is chiefly residential, but there is some industry. Products include sheet and fabricated metal, foods, and textiles.

Oak Lawn, village (1990 pop. 56,182), Cook co., NE Ill., a suburb of Chicago; inc. 1909. It is chiefly residential with some light manufacturing. Products include metalwork, wood products, and school supplies.

Oak Forest, village (1990 pop. 26,203), Cook co., NE Ill., a residential suburb of Chicago; inc. 1947. Oak Forest lies in a grain and livestock area. Industries include the manufacture of chemicals and commercial printing.

Oak Creek, city (1990 pop. 19,513), Milwaukee co., SE Wis., a suburb of Milwaukee, on Lake Michigan; inc. 1955. Electronic, plastic, paper, metal, and concrete products; machinery; computers; chemicals; and transportation equipment are made there. Truck farms dot the city's surrounding region.

Charter Oak, white oak tree that until 1856 stood in Hartford, Conn., and was thought to be 1,000 years old. There is a tradition that when Sir Edmund Andros, as governor-general of New England, demanded (1687) that the charter of Connecticut be surrendered by the colonists at Hartford, the document was hidden in a hollow of the tree.

Any of about 450 species of ornamental and timber trees and shrubs that make up the genus Quercus in the beech family, found throughout temperate climates. Oaks are deciduous trees that bear spring catkins (male flowers) and spikes (female flowers) on the same tree. The leaves have lobed, toothed, or smooth margins. The fruit is the acorn. They are hardy and long-lived shade trees. White oaks have smooth leaves and rapidly germinating sweet acorns; red, or black, oaks have bristle-tipped leaves and bitter, hairy acorns. Red- and white-oak lumber is used in construction, flooring, furniture, millwork, barrel making, and the production of crossties, structural timbers, and mine props. The genus includes many ornamentals and natural hybrids.

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Any of several North American ornamental and timber trees in the red-oak group of the genus Quercus in the beech family. The southern live oak (Q. virginiana) is a massive (50 ft, or 15 m, tall), durable evergreen tree. The trunk divides near the ground into several limbs that extend horizontally as much as two to three times the height of the tree. The elliptical leaves are dark green and glossy above, whitish and hairy below. A valuable timber tree, the southern live oak is also planted as a shade and avenue tree in the southern U.S. The oldest trees are 200–300 years old.

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