Stinging nettle

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.

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 4-merous 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 or serotonin, and possibly formic acid.

This mixture of chemical compounds cause a sting or paresthesia from which the species derives its common name, as well as the colloquial names burn nettle, burn weed, burn hazel. The pain and itching from a nettle sting can last from only a few minutes to as long as a week.




Source: http://en.wikipedia.org/wiki/Urtica_dioica


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