Nettles

Nettles

Nettles are between 30-45 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 names that will be encountered in this genus in the older literature (about 100 species have been described) 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.

Toxicity

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.

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 atrichocaulis Himalaya, southwestern China
• Urtica atrovirens western Mediterranean region
• 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 (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 (scrub nettle), Australia
• Urtica kioviensis Rogow. 1843, eastern Europe
• Urtica laetivirens Maxim. 1877, Japan, Manchuria
• Urtica linearifolia (creeping or swamp nettle), New Zealand
• Urtica mairei Himalaya, southwestern China, northeastern India,
• Myanmar
• Urtica membranacea Mediterranean region, Azores
• Urtica morifolia Canary Islands (endemic)
• Urtica parviflora Himalaya (lower altitudes)
• 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 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

Much historical evidence of use of nettles in medicine, folk remedies, cooking and fiber 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.

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.

Safety

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)

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)
• Nilgiri Nettle (Girardinia leschenaultiana)

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).
• Carolina horsenettle (Solanum carolinense) in the Solanaceae.
• Spurge-nettle (Cnidolscolus stimulosus) in the Euphorbiaceae.

See also

• Mopiko, a nettle rash cream
• Rumex, Dock leaves for sting easement and nullification of longer term effects
• Poison oak, Poison ivy, Poison sumac