Urtica

Urtica is a genus of flowering plants in the family Urticaceae. Many species have stinging hairs and may be called nettles or stinging nettles (the latter name applying particularly to U. dioica). The generic name Urtica derives from the Latin for 'sting'.

Due to the stinging hairs, Urtica are rarely eaten by herbivores, but provide shelter for insects. The fiber has historically been used by humans, and cooking preparations exist.

Description
Urtica 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 –. 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.

In 1874, while in Collioure (south of France), French botanist Charles Naudin discovered that a strong wind lasting 24 hours rendered the stinging hairs of nettles harmless for an entire week.

Phylogeny
The last common ancestor of the genus originated in Eurasia, with fossils being known from the Miocene of Germany and Russia, subsequently dispersing worldwide. Several species of the genus have undergone long distance oceanic dispersal, such as Hesperocnide sandwicensis (native to Hawaii) and Urtica ferox (native to New Zealand).

Species
A large number of species included within the genus in the older literature are now recognized as synonyms of Urtica dioica. Some of these taxa are still recognized as subspecies. Genetic evidence indicates that the two species of Hesperocnide are part of this genus.

Species in the genus Urtica, and their primary natural ranges, include:
 * Urtica andicola Webb
 * Urtica angustifolia Fisch. ex Hornem. China, Japan, Korea
 * Urtica ardens Link China
 * Urtica aspera Petrie South Island, New Zealand
 * Urtica atrichocaulis (Hand.-Mazz.) C.J.Chen Himalaya, southwestern China
 * Urtica atrovirens Req. ex Loisel. western Mediterranean region
 * Urtica australis Hook.f. South Island, New Zealand and surrounding subantarctic islands
 * Urtica cannabina L., Western Asia from Siberia to Iran
 * Urtica chamaedryoides Pursh (heartleaf nettle), southeastern North America
 * Urtica dioica L. (stinging nettle or bull nettle), Europe, Asia, North America
 * Urtica dioica subsp. afghanica Chrtek, from southwestern and central Asia, sometimes has stinging hairs or is sometimes hairless.
 * Urtica dioica subsp. dioica (European stinging nettle), from Europe, Asia, and northern Africa, has stinging hairs.
 * Urtica dioica subsp. gansuensis C.J.Chen, from eastern Asia (China), has stinging hairs.
 * Urtica dioica var. glabrata (Clem.) Asch. & Graebn.
 * Urtica dioica var. hispida (Lam. ex DC.) Tausch ex Ott
 * Urtica dioica var. holosericea Fr.
 * Urtica dioica subsp. kurdistanica Chrtek
 * Urtica dioica subsp. pubescens Ledeb. Domin, in many sources as U. dioica subsp. galeopsifolia (fen nettle or stingless nettle). Europe, Southwestern Russia east to Central Asia.
 * Urtica dioica subsp. sondenii (Simmons) Avrorin ex Geltman northeastern Europe, northern Asia
 * Urtica dioica var. sarmatica Zapał.
 * Urtica dioica subsp. subinermis (R.Uechtr.) Weigend
 * Urtica dubia – illegitimate synonym of U. membranacea
 * Urtica ferox G.Forst. (ongaonga or tree nettle), New Zealand
 * Urtica fissa E.Pritz. China
 * Urtica gracilenta Greene (mountain nettle), Arizona, New Mexico, west Texas, northern Mexico
 * Urtica gracilis Aiton (slender nettle), North America and parts of South America
 * Urtica hyperborea Jacquem. ex Wedd. Himalaya from Pakistan to Bhutan, Mongolia and Tibet, high altitudes
 * Urtica incisa Poir. (scrub nettle), Australia, New Zealand
 * Urtica kioviensis Rogow. eastern Europe
 * Urtica laetivirens Maxim. Japan, Northeast China
 * Urtica lalibertadensis Weigend
 * Urtica linearifolia (Hook.f.) Cockayne (creeping or swamp nettle), or Urtica perconfusa, an at risk endemic climber, New Zealand
 * Urtica mairei H.Lév. Himalaya, southwestern China, northeastern India, Myanmar
 * Urtica massaica Mildbr. Africa
 * Urtica membranacea Poir. ex Savigny Mediterranean region, Azores and Madeira
 * Urtica morifolia Poir. Macaronesia
 * Urtica minutifolia Griseb. Bolivia
 * Urtica parviflora Himalaya (lower altitudes)
 * Urtica peruviana D.Getltman Perú
 * Urtica pseudomagellanica D.Geltman Bolivia
 * Urtica pilulifera L. (Roman nettle), southern Europe
 * Urtica platyphylla Wedd. Kamchatka, Sakhalin, Japan
 * Urtica procera Mühlenberg (tall nettle), North America
 * Urtica rupestris Guss. Sicily (endemic)
 * Urtica taiwaniana S.S.Ying Taiwan
 * Urtica thunbergiana Siebold & Zucc. Japan, Taiwan
 * Urtica triangularis Hand.-Mazz.
 * Urtica urens L. (small nettle or annual nettle), Europe, North America
 * Urtica urentivelutina Weigend

Etymology
The generic name Urtica derives from the Latin for 'sting'.

Ecology
Due to the stinging hairs, Urtica species are rarely eaten by herbivores, but provide shelter for insects such as aphids, butterfly larvae, and moths. They are also consumed by caterpillars of numerous Lepidoptera (butterflies and moths), such as the tortrix moth Syricoris lacunana and several Nymphalidae, e.g. Vanessa atalanta, a red admiral butterfly.

Toxicity
Besides the stinging hairs in general, in New Zealand U. ferox is classified as a poisonous plant, most commonly upon skin contact.

Uses
Fabric woven of nettle fiber was found in burial sites in Denmark dating to the Bronze Age, and in clothing fabric, sailcloth, fishing nets, and paper via the process called retting (microbial enzymatic degradation, similar to linen processing). Other processing methods include mechanical and chemical.

Culinary
Urtica is an ingredient in soups, omelettes, banitsa, purée, and other dishes. In Mazandaran, northern Iran, a soup (Āsh) is made using this plant. Nettles were used in traditional practices to make nettle tea, juice, and ale, and to preserve cheeses, such as in Cornish Yarg.

Asian
Milarepa, the 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.

Caribbean
The Caribbean trickster figure Anansi appears in a story about nettles, in which he has to chop down a huge nettle patch in order to win the hand of the king's daughter.

European
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.

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). Alternatively, it may be recommending harvesting early in the year before the plants grow tall, as they become tough and stringy later.

The English figure of speech "grasp the nettle", meaning to nerve oneself to tackle a difficult task, stems from a belief that nettles actually sting less if gripped tightly. This belief gave rise to a well-known poem by Aaron Hill:
 * 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.
 * 'Tis the same, with common natures,
 * Use ’em kindly, they rebel:
 * But, be rough as Nutmeg-graters,
 * And the rogues obey you well.
 * And the rogues obey you well.

In Hans Christian Andersen's fairy-tale "The Wild Swans," the princess had to weave coats of nettles to break the spell on her brothers.

In the Brothers Grimm's fairy-tale "Maid Maleen", the princess and her maid must subsist on raw nettles while fleeing their war-ravaged kingdom. While standing in for the false bride during the wedding procession, she speaks to a nettle plant (which later proves her identity):
 * Oh, nettle-plant,
 * Little nettle-plant,
 * What dost thou here alone?
 * I have known the time
 * When I ate thee unboiled,
 * When I ate thee unroasted.