Three species of stinging nettles grow in the American southwest
Herbaceous with stinging and non-stinging hairs and with simple or branched stems that can grow to about nine feet high. U. d. gracilis is the only perennial of the three. It spreads from rhizomes, and it can be either erect or sprawling. The two annual species grow from a taproot and are erect. Leaves of all species are opposite, toothed, up to two inches long, and generally oval, elliptic or narrowly heart shaped. Caterpillars, including those of the painted lady, the red admiral and the satyr comma, consume the leaves. Tiny greenish flowers grow in dense drooping clusters at the leaf axils (where the leaf arises from the stem). Different species flower from spring to fall.
Stinging hairs, or trichomes, grow on stems and leaves. U. d. gracilis has the least hairy stems; they have a bulbous base and a stiff translucent apex. When brushed, the tip of the trichome breaks off, leaving a sharp, hypodermic needle-like point that injects chemical irritants into the skin. Non-stinging hairs are soft and flexible. Histamine, acetylcholine and 5-hydroxytryptamine are the primary irritating chemicals. Most stings require no treatment other than time.
Three species of stinging nettles grow in the American southwest: Urtica dioica (subspecies, Urtica dioica gracilis), Urtica gracilenta and Urtica urens. Urtica and urens are both derived from the Latin "uro," meaning to burn. Gracilenta means "slender," and dioica is derived from "dioecious," the term used to describe species in which male and female flowers grow on different plants. This is a bit of a misnomer considering that both sexes of flowers for our subspecies generally grow on the same plant. Other subspecies of U. dioica are dioecious, however. Some claim that the term "nettle" refers to the plant’s needle-like sting, while others trace the word’s origin to the plant’s use for weaving, hence the term "nettle" or "net-plant."
U. gracilenta occurs at higher elevations (3900 to 8250 feet) along shaded streams in alluvial soils. Plants are generally scattered and overlooked until brushed against. U. d. gracilis has much broader requirements, growing from sea level to over 9000 feet in moist woodlands and in disturbed habitats such as fence rows, orchards and gardens. It can often form dense clusters. The invasive U. urens is a classic weed with the widest habitat requirements, sprouting near old dwellings, waste areas and other disturbed sites, generally at elevations below 2300 feet.
U. gracilenta is restricted to southeastern Arizona and western New Mexico. U. d. gracilis is generally a northern plant, growing in the Rockies, up into Alaska and throughout Canada. It is found across New Mexico and in the easternmost part of Arizona. Like the other two species, U. urens has limited distribution in the desert, occurring only in Arizona along the Gila River.
People have used stinging nettles for rheumatism, upset stomach, fevers, colds, paralysis and numerous other ailments. Stinging nettles are edible, especially when young; they can be boiled and substituted for spinach.
During the middle ages, monks supposedly flagellated themselves with nettle for penance. Roman soldiers in England did the same thing to help them better adapt to the cold, damp climate. Native Americans helped themselves stay awake at night with a quick flagellation or two.
In the Hans Christian Anderson story, "The Wild Swans," the 11 brothers of a fair princess were trapped by an evil spell in the bodies of swans. The spell could be broken only if the princess made each brother a coat from nettles and didn’t utter a word the whole time she was doing it. As one might expect, she succeeded.
A relative of stinging nettles in Australia grows to over 120 feet in height. It has hairs that cause reactions lasting for weeks. Cold objects or water reactivate the symptoms.
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