NETTLE, the common name for the plants of the botanical genus Urtica, which gives its name to the family Urticaceae. It contains about 3o species found in the temperate parts of both hemispheres. They are herbs covered with stinging hairs, and with very small, greenish, unisexual flowers on the same or on different plants. The stinging hairs consist of an elongated tubular cell the extremity of which is finely pointed. By this point the hair penetrates the skin, breaks off and its contents pass out. The fluid contains formic acid and has a temporary irritant effect.
Nettle tops, or the very young shoots of the nettle, may be used as a vegetable like spinach; but from the abundance of crystals (cystoliths) they contain they are apt to be gritty. The fibre fur nished by the stems of several species is used for cordage or paper-making. Three species of nettle are wild in the British Isles: the common or great nettle (U. dioica), which is a hairy perennial with staminate and pistillate flowers in distinct plants; the small nettle (U. urens), which is annual and, except for the
stinging hairs, glabrous, and has staminate and pistillate flowers in the same panicle; and the Roman nettle (U. pilulifera), an annual with the pistillate flowers in rounded heads, which occurs in waste places in the east of England, chiefly near the sea—the most virulent British species.
In North America, where the small nettle has become natural ized across the continent and the great nettle, from Newfound land to Colorado and southward, there are several native nettles.
Among these are the tall nettle (U. gracilis), found across the continent northward ; the weak nettle (U. chamaedrioides), of the south-eastern States ; the hoary nettle (U. holosericea), found from Idaho and Washington to Lower California, and the Cali fornia nettle (U. californica). Closely allied are the wood nettle (Laportea canadensis), of the eastern United States, and the western nettle (Hesperocnide tenella), of California.