View source for Stinging nettle

{{Taxobox
| color = lightgreen
| name = Stinging nettle
| image = Brennnessel 1.JPG
| image_width = 240px
| image_caption = ''Urtica dioica'' subsp. ''dioica''
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Magnoliopsida]]
| ordo = [[Rosales]]
| familia = [[Urticaceae]]
| genus = ''[[Urtica]]''
| species = '''''U. dioica'''''
| binomial = ''Urtica dioica''
| binomial_authority = [[Carolus Linnaeus|L.]]
}}

The '''stinging nettle''' (''Urtica dioica'') is a [[herbaceous]] [[flowering plant]] native to [[Europe]], [[Asia]], northern [[Africa]], and [[North America]], and is the best known member of the [[nettle]] genus ''[[Urtica]]''.

The [[taxonomy]] of stinging nettles in the genus ''Urtica'' 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. ''afghanica''. Southwestern and central Asia.
*''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 [[synonymy|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, and bull nettle (a name shared by ''[[Cnidoscolus texanus]]'' and ''[[Solanum carolinense]]'').

[[Image:Euro stinging nettle.jpg|thumb|left|A young European stinging nettle]]
Stinging nettles are an [[herbaceous]] [[perennial]], growing to 1-2&nbsp;[[metre|m]] tall in the summer and dying down to the ground in winter. It has very distinctively yellow, widely spreading roots. The soft green [[leaf|leaves]] are 3-15&nbsp;[[centimetre|cm]] long, with a strongly serrated margin, a cordate base and an acuminate tip. Both the leaves and the stems are covered with brittle, hollow, silky hairs that were formerly thought to contain [[formic acid]] as a defence against grazing animals. Recent research has revealed the cause of the sting to be from three chemicals - a [[histamine]] that irritates the skin, [[acetylcholine]] which causes a burning sensation and [[serotonin]], that encourages the other two chemicals (Elliott 1997). Bare skin brushing up against a stinging nettle plant tends to break the delicate defensive hairs and release the trio of chemicals, usually resulting in a temporary and painful skin [[rash]] similar to [[poison ivy]], though the nettle's rash and duration are much weaker. It is possible to evade the sting by touching the middle of the [[leaf]] or by stroking in the same direction as the hairs.

Stinging nettles are abundant in northern Europe and much of Asia, usually found in the countryside. It is less gregarious 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 [[South Carolina]]{{Fact|date=March 2007}}, and also can be found in northernmost [[Mexico]]. In North America the stinging nettle is far less common than in northern Europe. The European subspecies has been introduced into North America as well as [[South America]]. 

In the [[United Kingdom|UK]] 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 in the soil, providing an ideal environment for stinging nettles. This seems particularly evident in [[Scotland]] where the sites of [[croft (land)|croft]]s razed to the ground during the [[Highland Clearances]] can still be identified.