Nettle (Urtica) is a genus of flowering plants in the family Urticaceae, mostly perennial herbs but some are annual and a few are shrubby. The most prominent member of the genus is the Stinging nettle Urtica dioica, native to Europe, 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 recognised as synonyms of Urtica dioica. Some of these taxa are still recognised as subspecies.
All the species listed below share the property of having stinging hairs, and can be expected to have very similar medicinal uses to the stinging nettle. The sting of Urtica ferox, the ongaonga or tree nettle of New Zealand, have been known to kill horses, dogs and at least one human.
Species in the genus Urtica, and their primary natural ranges, include:
Urtica angustifolia. China, Japan, Korea.
Urtica cannabina. Western Asia from Siberia to Iran.
Urtica dioica (Stinging nettle or Bull nettle). Europe, Asia, North America.
Urtica dubia (Large-leaved nettle) Canada.
Urtica ferox (Ongaonga or tree nettle). New Zealand.
Urtica hyperborea. Himalaya from Pakistan to Bhutan, Mongolia and Tibet, high altitudes.
Urtica incisa (Scrub nettle). Australia.
Urtica laetivirens. Japan, Manchuria.
Urtica parviflora. Himalaya (lower altitudes).
Urtica pilulifera (Roman nettle). Europe
Urtica platyphylla. China, Japan.
Urtica thunbergiana. Japan.
Urtica urens (Dwarf 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.
Nettles are the exclusive larval food plant for several species of butterfly and are also eaten by the larvae of some moths including Dot Moth, The Flame, The Gothic, Grey Chi, Grey Pug, Lesser Broad-bordered Yellow Underwing, Mouse Moth, Setaceous Hebrew Character and Small Angle Shades. The roots are sometimes eaten by the larva of the Ghost Moth Hepialus humuli.
Nettle stems are a popular raw material used in small-scale papermaking.
The tops of growing nettles are a popular cooked green in many areas, and are exceptionally high in protein. Some cooks throw away a first water to get rid of the formic acid, while others retain the water and cook the nettles straight. Nettle tops are sold in some farmers' markets and natural food stores. Nettle is believed to be a galactagogue and a clinical trial has shown that the juice is diuretic in patients with congestive heart failure.
Urtication, or flogging with nettles, is the process of deliberately applying stinging nettles to the skin in order to provoke inflammation. An agent thus used is known as a rubefacient (i.e. something that causes redness). This is done as a folk remedy for rheumatism, as it provides temporary relief from pain.
Extracts can be used to treat arthritis; it is also believed to be diuretic and uses treating hay fever are being investigated.
Nettle root extracts have been extensively studied in human clinical trials as a treatment for symptoms of benign prostatic hyperplasia (BPH). These extracts have been shown to help relieve symptoms compared to placebo both by themselves and when combined with other herbal medicines.
The traditional remedy for nettle stings is rubbing with the leaf of the dock plant, Rumex obtusifolus, which often grows beside nettles in the wild. While there is no scientific evidence that this remedy works, searching for and using a dock leaf at least takes the mind off the stinging pain somewhat.
Though the fresh leaves can cause painful stings, these are rarely seriously harmful. Otherwise most species of nettles are extremely safe and some are even eaten as vegetables after being steamed to remove the stingers.