|Stinging nettle (Urtica dioica)|
Nettles constitute between twenty-four and thirty-nine species of flowering plants of the genus Urtica in the family Urticaceae, with a cosmopolitan though mainly temperate distribution. They are mostly herbaceous perennial plants, but some are annual and a few are shrubby. Most of the species have stinging hairs on the stems and leaves.
The most prominent member of the genus is the stinging nettle, Urtica dioica, native to Europe, Africa, Asia, and North America. The genus also contains a number of other species with similar properties, listed below. However, a large number of species included within this genus in the older literature are now recognized as synonyms of Urtica dioica. Some of these taxa are still recognized as subspecies.
Urtica nettles are food for the caterpillars of numerous Lepidoptera (butterflies and moths), such as the tortrix moth Syricoris lacunana and several Nymphalidae, such as Vanessa atalanta, one of the Red Admiral butterflies.
Vegetative characteristics 
Nettle species grow as annuals or perennial herbaceous plants, rarely shrubs. They can reach, depending on the type, location and nutrient status, a height of 10–300 cm. The perennial species have underground rhizomes. The green parts have stinging hairs. Their often quadrangular stems are unbranched or branched, erect, ascending or spreading.
Most leaves and stalks are arranged across opposite sides of the stem . The leaf blades are elliptic, lanceolate, ovate or circular. The leaf blades usually have three to five, rarely up to seven veins. The leaf margin is usually serrate to more or less coarsely toothed. The often-lasting bracts are free or fused to each other. The Cystoliths are extended to more or less rounded.
The nature of the toxin secreted by nettles is not settled. The stinging hairs of most nettle species contain formic acid, serotonin and histamine; however recent studies of Urtica thunbergiana implicate oxalic acid and tartaric acid rather than any of those substances, at least in that species.
Species of nettle 
Species in the genus Urtica, and their primary natural ranges, include:
- Urtica angustifolia Fisch. ex Hornem. 1819, China, Japan, Korea
- Urtica ardens China
- Urtica aspera Petrie South Island, New Zealand
- Urtica atrichocaulis Himalaya, southwestern China
- Urtica atrovirens western Mediterranean region
- Urtica australis Hook.f. South Island, New Zealand and surrounding subantarctic islands
- Urtica cannabina L. 1753, Western Asia from Siberia to Iran
- Urtica chamaedryoides (heartleaf nettle), southeastern North America
- Urtica dioica L. 1753 (stinging nettle or bull nettle), Europe, Asia, North America
- Urtica dubia (large-leaved nettle), Canada
- Urtica ferox G.Forst. (ongaonga or tree nettle), New Zealand
- Urtica fissa China
- Urtica galeopsifolia Wierzb. ex Opiz, 1825, (fen nettle or stingless nettle). Europe. (Often considered a subspecies of Urtica dioica)
- Urtica gracilenta (mountain nettle), Arizona, New Mexico, west Texas, northern Mexico
- Urtica hyperborea Himalaya from Pakistan to Bhutan, Mongolia and Tibet, high altitudes
- Urtica incisa Poir (scrub nettle), Australia, New Zealand
- Urtica kioviensis Rogow. 1843, eastern Europe
- Urtica laetivirens Maxim. 1877, Japan, Northeast China
- Urtica linearifolia (Hook.f.) Cockayne (creeping or swamp nettle), New Zealand
- Urtica mairei Himalaya, southwestern China, northeastern India, Myanmar
- Urtica massaica Africa
- Urtica membranacea Mediterranean region, Azores
- Urtica morifolia Canary Islands (endemic)
- Urtica parviflora Himalaya (lower altitudes)
- Urtica peruviana D.Getltman, 1981, Perú
- Urtica pseudomagellanica D.Geltman, 1983, Bolivia
- Urtica pilulifera (Roman nettle), southern Europe
- Urtica platyphylla Wedd. 1856-1857, China, Japan
- Urtica procera Mühlenberg (tall nettle), North America
- Urtica pubescens Ledeb. 1833, Southwestern Russia east to central Asia
- Urtica rupestris Sicily (endemic)
- Urtica sinuata Bl. (Fever Nettle or Elephent nettle), subtropical Asia
- Urtica sondenii (Simmons) Avrorin ex Geltman, 1988, northeastern Europe, northern Asia
- Urtica taiwaniana Taiwan
- Urtica thunbergiana Japan, Taiwan
- Urtica triangularisa
- Urtica urens L. 1753 (small nettle or annual nettle), Europe, North America
The family Urticaceae also contains some other plants called nettles that are not members of the genus Urtica. These include the wood nettle Laportea canadensis, found in eastern North America from Nova Scotia to Florida, and the false nettle Boehmeria cylindrica, found in most of the United States east of the Rockies. As its name implies, the false nettle does not sting.
Uses and medical properties of nettles 
||This section needs additional citations for verification. (November 2011)|
Much historical evidence of use of nettles in medicine, folk remedies, cooking and fibre production relate to one species - Urtica dioica, but a fair amount also refers to the use of Urtica urens, the small nettle, which is preferred because it has more stinging hairs per leaf area than the more common species. It may be inappropriate and probably inaccurate to assume that all nettles exhibit similar properties in all cases, but where an action can be attributed to principles found in the species, such as histamine, choline, formic acid and silica, a rational basis for their use is still available. However, the fact that a medical action can be attributed to a single constituent does not imply that the entire plant will have the same action.
Arthritic joints were traditionally treated by whipping the joint with a branch of stinging nettles. The theory was that it stimulated the adrenals and thus reduced swelling and pain in the joint. Various studies support the effectiveness of this treatment.
Various types of Nettle have been studied for their effects on prostate hypertrophy, diabetes mellitus, rheumatic disease, hypertension, gastrointestinal symptoms, osteoarthritis, diarrhea, rheumatoid arthritis, inflammation, pain, constipation, gastrointestinal disease, headache, nausea, common cold, arthritis, asthma, bleeding, respiratory tract disease, allergic rhinitis, kidney disease, prostate cancer, skin disease and urinary tract disease. In terms of allergies, nettle contains properties of an antihistamine to be used for treating reactions associated with the respiratory system. Nettles can also be used to make a tisane known as "nettle tea".
Prehistoric use 
In folklore 
Myths about health and wealth 
- Nettles in a pocket will keep a person safe from lightning and bestow courage.
- Nettles kept in a room will protect anyone inside.
- Nettles are reputed to enhance fertility in men, and fever could be dispelled by plucking a nettle up by its roots while reciting the names of the sick man and his family.
Milarepa, the great Tibetan ascetic and saint, was reputed to have survived his decades of solitary meditation by subsisting on nothing but nettles; his hair and skin turned green and he lived to the age of 83. 
An old Scots rhyme about the nettle:
- "Gin ye be for lang kail coo the nettle, stoo the nettle
- Gin ye be for lang kail coo the nettle early
- Coo it laich, coo it sune, coo it in the month o' June
- Stoo it ere it's in the bloom, coo the nettle early
- Coo it by the auld wa's, coo it where the sun ne'er fa's
- Stoo it when the day daws, coo the nettle early."
- (Old Wives Lore for Gardeners, M & B Boland)
Coo, cow, and stoo are all Scottish for cut back or crop (although, curiously, another meaning of "stoo" is to throb or ache), while "laich" means short or low to the ground. Given the repetition of "early," presumably this is advice to harvest nettles first thing in the morning and to cut them back hard [which seems to contradict the advice of the Royal Horticultural Society].
A well-known English rhyme about the stinging nettle is:
- Tender-handed, stroke a nettle,
- And it stings you for your pains.
- Grasp it like a man of mettle,
- And it soft as silk remains.
Role in the environment 
Thanks to the stinging hairs, nettles are rarely eaten by herbivores, so they provide long-term shelter for insects, such as aphids or caterpillars of many butterflies and moths. The insects, in turn, provide food for small birds, such as tits.
Though the fresh leaves can cause painful stings and acute urticaria, these are rarely seriously harmful. A possible exception is the Urtica ferox, the ongaonga or tree nettle of New Zealand. Otherwise most species of nettles are extremely safe and some are even eaten as vegetables after being steamed.
Similar stinging plants 
Other members of other genera in the Urticaceae, with powerful stings:
- Giant stinging tree (Dendrocnide excelsa)
- Gympie (Dendrocnide moroides)
- Wood Nettle (Laportea canadensis)
- Nettle Tree (Urera baccifera)
- Nilgiri Nettle, Himalayan Giant Nettle (Girardinia diversifolia, synonym: G. leschenaultiana), source of Allo fiber
There are also plants which can produce stinging sensations but which are unrelated to the Urticaceae:
- Dumb cane (Dieffenbachia spp., Araceae)
- Cowhage (Mucuna pruriens, Fabaceae)
- Bull Nettle or Spurge Nettle (Cnidoscolus stimulosus, Euphorbiaceae)
- Ciega-vista (Croton ciliato-glandulosus, Euphorbiaceae)
- Stinging Spurge (Jatropha urens L., Euphorbiaceae)
- Noseburn (Tragia spp., Euphorbiaceae)
Similarly named plants 
Plants with common names include the word "nettle" but which do not sting nor are they part of Urticacea':
- Dead-nettle (Lamium spp.) and woundwort or hedge-nettle (Stachys spp.) which are in the Lamiaceae or mint family.
- Devil's nettle, or yarrow (Achillea).
See also 
- Kopriva, a surname meaning nettle
- Mopiko, a nettle rash cream
- Poison ivy, Poison oak, Poison sumac
- Rumex, Dock leaves for sting easement and nullification of longer term effects
- Fu, H. Y.; Chen, S. J.; Chen, R. F.; Ding, W. H.; Kuo-Huang, L. L.; Huang, R. N. (2006). "Identification of oxalic acid and tartaric acid as major persistent pain-inducing toxins in the stinging hairs of the nettle, Urtica thunbergiana". Annals of Botany (London) 98 (1): 57–65. doi:10.1093/aob/mcl089.
- Randall C, Randall H, Dobbs F, Hutton C, Sanders H (2000 Jun), "Randomized controlled trial of nettle sting for treatment of base-of-thumb pain", Journal of the Royal Society of Medicine 93 (6): 305–309, PMC 1298033, PMID 10911825
- Chrubasik S, Enderlein W, Bauer R, Grabner W. (1997). Evidence for the antirheumatic effectiveness of herba urticae dioicae in acute arthritis: A pilot study. Phytomedicine 4: 105-108.
- Marrassini, C.; Acevedo, C.; Miño, J.; Ferraro, G.; Gorzalczany, S. (2010). "Evaluation of antinociceptive, antinflammatory activities and phytochemical analysis of aerial parts of Urtica urens L.". Phytother Res 24 (12): 1807–1812. doi:10.1002/ptr.3188.
- Gulsel M. Kavalali (2003), Gulsel M. Kavalali, ed., Urtica: Therapeutic and Nutritional Aspects of Stinging Nettles, Taylor and Francis, p. 13, ISBN 0-415-30833-X
- Gtsaṅ-smyon He-ru-ka, Heruka Tsangnyon, Andrew Quintman, Donald S. Lopez, Jr. (2003), The Life of Milarepa, Penguin, p. 139, ISBN 0-14-310622-8
- Caribbean folktales
- Dictionary of the Scots Language (online)
- Butterflies of the nettle patch
- Moths of the nettle patch
- Nettles and Wildlife by Prof. Chris Baines
- Rohde, M. (1988-2006). "Guide to Contact-Poisonous Plants". mic-ro.com. Retrieved 2010-02-12.
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (February 2010)|
- Anderberg, Kirsten (2005). Folk uses and history of medicinal uses of nettles. Nettles, Nettles, Everywhere
- Dathe G, Schmid H. (1987). Phytotherapy for benign prostatic hyperplasia (BPH): Double-blind study with extract of root of urtica (ERU). Urologe B 27: 223-226 [in German].
- Holden, Margaret (1948), "An alkali-producing mechanism in macerated leaves", Biochemical Journal 42 (3): 332–336, PMC 1258718, PMID 16748291.
- Kirchhoff HW. (1983). Brennesselsaft als Diuretikum. Z. Phytother. 4: 621-626 [in German].
- Krzeski T, Kazón M, Borkowski A, et al. (1993). Combined extracts of Urtica dioica and Pygeum africanum in the treatment of benign prostatic hyperplasia: double-blind comparison of two doses. Clinical Therapy 15 (6): 1011-1020.
- Mittman, P. (1990). Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. Planta Med 56: 44-47.
- Randall C, Randall H, Dobbs F, et al. (2000). Randomized controlled trial of nettle sting for treatment of base-of-thumb pain. J. Roy. Soc. Med. 93: 305-309. reported online in British Medical Journal
- Weigend M, Luebert F. (2009). Weeding the nettles I: Clarifying species limits in perennial, rhizomatous Urtica (Urticaceae) from southern and central Chile and Argentina. Phytotaxa 2: 1-12.
- Yarnell E. (1998). Stinging nettle: A modern view of an ancient healing plant. Alt. Compl. Therapy 4: 180-186 (review).
- Healthy Life Magazine, Inc. (June 2007) p. 78
- Nettles and Wildlife
- Flora Europaea: Urtica from the Royal Botanic Garden Edinburgh website
- Flora of North America: Urtica from efloras.org
- Flora of China: Urtica from efloras.org
- Database search for Nettle from Plants for a Future