Stinging Nettle



be-careful of this plant if you see it. they sting the skin when touched 
Stinging nettle or common nettle, Urtica dioica, is a herbaceous perennial flowering plant, native to Europe, Asia, northern Africa, and North America, and is the best-known member of the nettle genus Urtica. The plant has many hollow stinging hairs called trichomes on its leaves and stems, which act like hypodermic needles, injecting histamine and other chemicals that produce a stinging sensation when contacted by humans and other animals. The plant has a long history of use as a medicine and as a food source.
Stinging nettle is a dioecious herbaceous perennial, 1 to 2 m (3 to 7 ft) tall in the summer and dying down to the ground in winter. It has widely spreading rhizomes and stolons, which are bright yellow as are the roots. The soft green leaves are 3 to 15 cm (1 to 6 in) long and are borne oppositely on an erect wiry green stem. The leaves have a strongly serrated margin, a cordate base and an acuminate tip with a terminal leaf tooth longer than adjacent laterals. It bears small greenish or brownish numerous flowers in dense axillary inflorescences. The leaves and stems are very hairy with non-stinging hairs and also bear many stinging hairs (trichomes), whose tips come off when touched, transforming the hair into a needle that will inject several chemicals: acetylcholine, histamine, 5-HT (serotonin), moroidin, leukotrienes, and possibly formic acid. This mixture of chemical compounds cause a painful sting or paresthesia from which the species derives its common name, as well as the colloquial names burn nettle, burn weed, burn hazel.
The taxonomy of stinging nettles has been confused, and older sources are likely to use a variety of systematic names for these plants. Formerly, more species were recognised than are now accepted. However, there are at least five clear subspecies, some formerly classified as separate species:
U. dioica subsp. dioica (European stinging nettle). Europe, Asia, northern Africa.
U. dioica subsp. galeopsifolia (fen nettle or stingless nettle). Europe. (Sometimes known as Urtica galeopsifolia)
U. dioica subsp. afghanica. Southwestern and central Asia. (Gazaneh in Iran)
U. dioica subsp. gansuensis. Eastern Asia (China).
U. dioica subsp. gracilis (Ait.) Selander (American stinging nettle). North America.
U. dioica subsp. holosericea (Nutt.) Thorne (hairy nettle). North America.
Other species names formerly accepted as distinct by some authors but now regarded as synonyms of U. dioica include U. breweri, U. californica, U. cardiophylla, U. lyalli, U. major, U. procera, U. serra, U. strigosissima, U. trachycarpa, and U. viridis. Other vernacular names include tall nettle, slender nettle, California nettle, jaggy nettle, burning weed, fire weed and bull nettle (a name shared by Cnidoscolus texanus and Solanum carolinense).
Stinging nettles are abundant in northern Europe and much of Asia, usually found in the countryside. It is less widespread in southern Europe and north Africa, where it is restricted by its need for moist soil. In North America it is widely distributed in Canada and the United States, where it is found in every province and state except for Hawaii and also can be found in northernmost Mexico. It grows in abundance in the Pacific Northwest, especially in places where annual rainfall is high. In North America the stinging nettle is far less common than in northern Europe[citation needed]. The European subspecies has been introduced into North America as well as South America.
In Europe stinging nettles have a strong association with human habitation and buildings. The presence of nettles may indicate that a building has been long abandoned. Human and animal waste may be responsible for elevated levels of phosphate and nitrogen in the soil, providing an ideal environment for stinging nettles.
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