Nettle
Nettle, a weed with stinging hairs. The name is especially applied to the 30 species of the genus Urtica, of which 9 species are found in the United States and Canada. Nettles are common in old pastures and other untended fields, and often invade gardens and cultivated fields. They are controlled by hoeing, by pulling up the plants (with gloved hands), or by spraying with herbicides.
Nettle hairs are hollow and brittle. When touched the tips break off, leaving sharp points that penetrate the skin. At the same time a tiny amount of formic acid—a strong irritant also produced by ants—is injected into the skin from a bulb at the base of each hair. This causes a burning sensation that lasts about half an hour. It is relieved by applying vinegar or the juice of dock or jewelweed.
The stinging nettle, or great nettle, native to Europe and Asia, is widely naturalized in the United States. This species grows up to three feet (90 cm) tall, with oval or heart-shaped, toothed leaves as much as five inches (13 cm) long, and with clusters of small greenish flowers.
The fibers of several species are woven into cloth in parts of southern Asia and in some of the islands of the South Pacific. A species grown in India has tubers on the roots; these tubers are eaten.
Several other prickly weeds are called nettles. Examples are the horse nettle of the nightshade family and the hemp nettle and the dead nettle of the mint family.
Nettles belong to the family Urticaceae. The stinging nettle is Urtica dioica. The tuber-producing nettle of India is U. tuberosa.