hemp, common name for a tall annual herb (Cannabis sativa) of the family Cannabinaceae, native to Asia but now widespread because of its formerly large-scale cultivation for the bast fiber (also called hemp) and for the drugs it yields. Known and cultivated in ancient China, the plant was introduced into Europe before the Christian era. In the United States it was cultivated for fiber chiefly in the Midwest, but competition from synthetic materials led to reduced crops, and antidrug legislation led to a federal ban (1970) on hemp growing without a permit. Federal legislation in 2014 eased restrictions on the growing of industrial hemp (which has very little drug content) for research purposes, and additional legislation in 2018 permitted the regulated commercial growing of industrial hemp. The fiber, retted from the stem, was one of the most important for various kinds of cordage; it was also used in making paper, cloth (canvas and other kinds), oakum for calking ships, and other products. The male and female flowers are borne on separate plants. The chemical derived from the female flowering tops in strains bred for their drug content is used medicinally; the tops are also the source of marijuana and hashish. Hemp seed is used as bird food, and the oil from the seeds is used in the manufacture of paints, varnishes, and soap and in cooking. The dried leaves are used in Asia for a beverage. The word hemp is used in combination for several other kinds of fiber plants, notably Manila hemp and sisal hemp. The true hemp plant is related to the hop, which is used in making beer. Hemp is classified in the division Magnoliophyta, class Magnoliopsida, order Urticales, family Cannabinaceae.
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