Stinging nettle

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{{Taxobox | color = lightgreen | name = Stinging nettle | image = Brennnessel 1.JPG | image_width = 240px | image_caption = Urtica dioica subsp. dioica | regnum = Plantae | divisio = Magnoliophyta | classis = Magnoliopsida | ordo = Rosales | familia = Urticaceae | genus = Urtica | species = U. dioica | binomial = Urtica dioica | binomial_authority = L. }} Image:Urtica dioica.JPG

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.

1 Taxonomy
2 Form
3 Occurrence
4 Uses
5 Influence on language and culture
6 References and external links

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Taxonomy

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 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

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Form

The stinging nettle is a herbaceous perennial, growing to 1-2 m tall in the summer and dying down to the ground in winter. It has very distinctively yellow, widely spreading roots. The soft green leaves are 3-15 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 thought to contain formic acid as a defence against grazing animals; but recent research has revealed the cause of the sting to be from three chemicals - a histamine to irritate the skin, acetylcholine to bring on a burning sensation and hydroxytryptamine to encourage the other two chemicals (Elliott 1997). Bare skin brushing up against a stinging nettle plant will break the delicate defensive hairs and release the trio of chemicals, usually resulting in a temporary and painful skin rash. One folk remedy for the sting is to treat the affected part with juice from the crushed leaf of a dock (Rumex obtusifolia), which commonly grows in association with nettles; it is not a very effective remedy.

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Occurrence

It is abundant in northern Europe and much of Asia, found widely in the countryside. It is less frequent 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, Arkansas, and South Carolina, and also occurs locally south into northernmost Mexico. However, in North America, the stinging nettle is markedly less common than in northern Europe. The European subspecies has also been introduced into North America. Away from its native area, the species has also been introduced to South America.

In the UK it has a strong association with human habitation and buildings. Sites of long abandoned buidings can often be deduced from the presence of nettles. This is believed to relate to elevated levels of phosphate in soils from human and animal waste. This is particularly evident in Scotland where the sites of crofts razed to the ground during the Highland Clearances can still be identified.

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Uses

Despite its sting, it has many uses. It is recommended by the herbalists of many different cultures for a wide variety of purposes in herbal medicine. Cooking, crushing or chopping disables the stinging hairs, and the leaves are not only tasty, but high in nutrients. The young leaves are edible and make a very good pot-herb. A simple recipe is to gather the upper stalks including 3-4 pairs of leaves before the plants flower (using gloves), until one has enough to entirely fill a small saucepan. Fill the pan with cold water, and then put on a lid and drain off the water until all that remains is what is clinging to the leaves. Then put the pan on high heat and steam the leaves, shaking the pan occasionally, until all the leaves are wilted. The leaves can also be dried and used to make a tisane.

In the maintenance of buildings there is a historic practical use of the drained off water as it is acid in nature and was used as an effective way of neutralising the alkaline salts evident on the walls of older damp houses. The salt contaminated patches on the walls continue to 'look' damp even after effective damp resistant course has been inserted. This is due the fact that the crystals have hygroscopic properies i.e. moisture attracting.

Nettle stems contain a bast fibre which has been traditionally used for the same purposes as linen, and is produced by a similar retting process. Nettles can also be used as cattle fodder; cows appear to find harvested nettles a delicacy.

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Influence on language and culture

Image:Illustration Urtica dioica0.jpg In England the stinging nettle is the only common stinging plant, and has found a place in several figures of speech in the English language. To "nettle" someone is to annoy them. Shakespeare's Hotspur urges that "out of this nettle, danger, we grasp this flower, safety" (Henry IV, part 1, Act II Scene 3). The common figure of speech "to grasp the nettle" probably originated as a condensation of this quotation. It means to face up to or take on a problem that has been ignored or deferred. The metaphor refers to the fact that if a nettle leaf is grasped firmly rather than brushed against, it does not sting so readily, because the hairs are crushed down flat and do not penetrate the skin so easily. However the sting of nettles has been recommended to relieve the pain of rheumatism as the effects of the sting can last up to twelve hours. The stinging feeling becomes a warm feeling on the area treated so helping the pain of the rheumatism to subside.

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