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Poison sumac, Rhus vernix
sumac or sumach [key], common name for some members of the Anacardiaceae, a family of trees and shrubs native chiefly to the tropics but ranging into north temperate regions and characterized by resinous, often acrid, sap. The sap of certain of these plants—especially poison ivy and related species of the New World genus Toxicodendron—contains an essential oil that can cause dermatitis. In these and other species the sap is also a major source of tannin, e.g., the quebracho tree of Paraguay, the lacquer tree of SE Asia, and the terebinth or turpentine tree and the mastic trees of the Mediterranean area. The pistachio, cashew, and mango provide important foods both for local consumption and for trade. The resin content is responsible for the acid taste of mango and cashew fruits and of the oil (sometimes extracted) in pistachio and cashew nuts. The true sumacs belong to the genus Rhus; some botanists include the poison ivy, poison oak, and poison sumac in that genus. Several species of sumacs are native to North America, usually in dry areas, and are noted for their brilliant autumn coloration. The common staghorn sumac (R. typhina) of the Eastern states is one of the species whose fruit is used in wine making and for medicinal purposes. Some sumacs—e.g., the Sicilian sumac (R. coriara) of S Europe—are cultivated for their tannin. Sumacs are also cultivated as ornamentals, e.g., the smoke tree (Cotinus coggygria) of S Eurasia, whose bark is sometimes used for a dye, and the pepper tree, or Peruvian mastic (Schinus molle), of the American tropics. The latter, with its drooping branches and red fruits, is a favorite avenue ornamental in S California; however, it is highly susceptible to black scale, a disease destructive to fruit trees, and hence must be destroyed in areas where there are citrus groves. Sumac is classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Anacardiaceae.
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