| Nettle | |
|---|---|
| Stinging nettle (Urtica dioica) | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Rosales |
| Family: | Urticaceae |
| Genus: | Urtica L., 1753 |
| Species | |
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Nettles constitute between 24 and 39 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.
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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.
Most of the species listed below share the property of having stinging hairs, and might be expected to have similar medicinal uses to the stinging nettle. The stings of Urtica ferox, the ongaonga or tree nettle of New Zealand, have been known to kill horses, dogs and at least one human.[1]
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.[2]
Species in the genus Urtica, and their primary natural ranges, include:
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.
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. 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,[3] 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.[4] In terms of allergies, nettle contains properties of an antihistamine to be used for treating reactions associated with the respiratory system.[5]
Fabric woven of nettle fiber has been found in burial sites dating back to the Bronze Age.[6]
Nettles have many folklore traditions associated with them. The folklore mainly relates to the stinging nettle (Urtica dioica), but confusion with the similar non-stinging Lamium was common.
Nettles in a pocket will keep a person safe from lightning and bestow courage.
Nettles kept in a room will protect anyone inside. (This may have arisen from common knowledge of the tremendous amount of nutrients nettles offer, making them a powerful plant in that sense.)
Arthritic joints were sometimes 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. A controlled study in the year 2000 supports the effectiveness of this treatment.[7]
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.
Turkey and other poultry (as well as cows and pigs) are said to thrive on nettles, and ground dried nettle in chicken feed will increase egg production.[8]
A distillation of the flowers of the White Archangel, or white dead-nettle (Lamium album) is reputed "to make the heart merry, to make a good colour in the face, and to make the vital spirits more fresh and lively." [9]
In 1926, the Royal Horticultural Society's recommendation for getting rid of nettles was to cut them down three times in three consecutive years, after which they will disappear.
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. [10]
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.[11]
An old Scots rhyme about the nettle:
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.[12] 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:
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.
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[13] and moths.[14] The insects, in turn, provide food for small birds, such as tits.[15]
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.[16]
Other members of other genera in the Urticaceae, with powerful stings:
There are also plants which can produce stinging sensations but which are unrelated to the Urticaceae:[17]
Plants with common names include the word "nettle" but which do not sting nor are they part of Urticacea':