nettle, common name for the Urticaceae, a family of fibrous herbs, small shrubs, and trees found chiefly in the tropics and subtropics. Several genera of nettles are covered with small stinging hairs that on contact emit an irritant (formic acid) which produces a skin rash sometimes called urticaria (see hives). The tropical American genus Urera is very powerful and sometimes dangerous. Stinging nettles in the United States include species of Urtica, widely distributed, and Laportea canadensis, a characteristic plant of eastern forests. L. gigas, the Australian nettle tree, reaches 90 ft (27.4 m) in height. Various plants of the family supply fiber, e.g., ramie, or China grass ( Boehmeria nivea ), native to SE Asia. Its valuable fiber is extremely strong, silky, and durable, but very difficult to extract. Because of the high quality of its various products (e.g., fabric, paper, and cordage) it has been cultivated experimentally in the United States and other countries. The young foliage of many temperate nettles supplies edible greens that are cooked like spinach. Various unrelated plants are sometimes also called nettles, e.g., the Old World nettle trees of the elm family and the prickly horse nettle of the nightshade family. The nettle family is classified in the division Magnoliophyta, class Magnoliopsida, order Urticales.