Some similarities to : Small Nettle but Small Nettle is smaller, has much shorter catkins, and the leaves are more rounded. Small Nettle stings more strongly than does Stinging Nettle, and it is an annual with white roots (whereas Stinging Nettle a perennial with yellow roots).

Slight resemblance to : Fen Nettle, but Fen Nettle grows on the Fens and has narrower leaves. Fen Nettle also does not sting as much as does Stinging Nettle.

Distinguishing Feature : the pendulous catkins, the hairs and the stinging rash that results from brushing against the leaves or stems.

Not to be confused with : Mint / Dead-Nettle Family [Labiatea / Lamiaceae]

The trichomes of Stinging Nettles are made of fine hollow needles of silica, being the hairs that do the stinging. The trichomes are so sharp that just a gentle brush of the back of the hand is sufficient for the trichomes to penetrate skin and inject a cocktail of substances. It is commonly thought that the compound which caused the pain was formic acid (the same substance which stinging ants inject) but that is now known to be untrue. A concoction of up to six other substances which irritate the skin and cause inflammation, the effects of which can last a considerable time, is now thought to be involved. Although very painful, the sting of Small Nettle (Urtica urens) is said to be more painful, possibly because it has more stinging trichomes (but there could be secondary metabolite reasons too, such as differing more potent irritants, or more of one than another).

It is often claimed that if the plant is grasped purposely and with great conviction then the stings do not get a chance to penetrate the skin. It is also said that because the stinging hairs are angled upwards, if the plant is gently grabbed by the main stem whilst moving the hand upwards a sting will be avoided (which is not so if you move your hand downwards). If the unsuspecting person does get stung, then it is advised they should not touch that part of their skin for 10 mins, however painful. Untouched, the pain will dissipate fairly rapidly, otherwise it may throb for several days. Folk-lore remedies advocate the rubbing of the stinging area with large Dock leaves, but whether this just mechanically removes the stinging hairs (or applies some neutralising chemical to counteract the irritant substance) is not known. As the season progresses the stings gradually lose both their effectiveness and ability to sting as the trichomes drop off, and are said not to sting if there is an 'r' in the month (meaning September to April - although whether this holds strictly true is up to the reader to assess).

Stinging Nettle is dioecious with male and female flowers on separate plants whereas Small Nettle is monoecious. The male flowers are yellowish or purplish starting out as near-spherical green bobbles, strung out in drooping tassels or catkins that do not droop very much. When open they have four very narrow but longish (in relation to their minuscule size) stamens out-stretched like petals into a cross. The female flowers tassels or catkins tend to droop much more, dangle would be more appropriate, are slightly smaller but still roundish, and are greenish with fuzzy white stigmas (when opened) or green when not yet open.

The stems contain coarse fibres that have in the past 2000 years been used to make textiles and clothing. As recently as World War I the German Army made their uniforms out of the fibres when cotton became scarce.

The Romans introduced Roman Nettle (Urtica pilulifera) which is monoecious and an annual and which reportedly has a worse sting but it does not seem to have been spotted in the wild in the UK since the advent of the 21st century. The Romans used to keep themselves warm by beating their skin with this stinging plant. Flagellation beats everything. It has large green spheres covered in stinging hairs.

MONOAMINES Amongst the liquid concoction within the stinging hairs are three mammalian neuro-transmitters, serotonin, histamine and acetylcholine, but although all three are super-irritants, experimental injection under the skin still does not unleash the full stinging experience of nettles. Therefore other substance(s) must also be involved. Many research papers mention Formic Acid (H•COOH) as being a constituent of Nettle stings, and many other research papers omit mention of formic acid in the sting whilst citing histamine and acetylcholine as the constituents. Others mention the Leukotrienes detailed below. Without the means to chemically examining the stings himself, your Author can only report this discrepancy. It could be that everyone is right, Nettle is a growing plant responding to threat levels autonomously, as do a great many other plants. There is no point in the plant manufacturing all the defence chemicals if it is not under threat, as this takes energy that could be better spent in growing or flowering.

MOROIDIN It is claimed by some texts that the bicyclic octapeptide moroidin is also found in nettle stings, and that it is this compound that is responsible for most of the pain and redness of nettle rash. It was first discovered in the trichomes of Laportea moroides (hence the name), otherwise known as the Gympie Bush, with which contact is a far more terrifying ordeal than is Stinging Nettle, for the painful rash can last for months, or even forever, and there is no cure. Moroidin has anti-mitotic activity because it strongly inhibits the polymerization of tubulin, meaning it interferes with cell division. Moroidin is structurally related to a whole family of Celogentins, which are present in the seeds of the plant Celosia argentea which belongs to the (Amaranthaceae family). The three highly unusual bonds in Moroidin are shown in red. These substances are bicyclic peptides and tend to be highly resistant to digestion within the stomach and can persist in the digestive tract. Although not present in Nettle, there also exists a plethora of other bicyclic polypeptides such as α-Amanitin, the highly toxic principle responsible for many fatalities after consuming Death Cap (Amanita phalloides) mushrooms. Cyclosporin A, a synthetic mono-cyclic polypeptide is used as an immunosuppressant drug in organ transplants. Echinomycin is another bicyclic polypeptide produced within various bacteria and is used medicinally as an antibiotic. There are hundreds more.

LEUKOTRIENES Both Leukotriene C4 and Leukotriene B4, which are constituents of snake venoms, are also found in nettle stings. Both Histamine and the Leukotrienes (of which there are many) are naturally produced by the human body as part of the inflammatory response. The cysteinyl Leukotrienes (such as LTC4, but not LTB4) are responsible for the symptoms of asthma (especially the bronchial constriction) and for anaphylactic shock, both of which are life-threatening conditions. It is strange that the body could so over-react to foreign substances (producing the chemicals histamine and leukotrienes in response) that those produced chemicals could kill them when the foreign substance initiating the response in the first place was relatively benign! So much stranger then that stinging nettle produces histamines and leukotrienes as that foreign substance.

Dock leaves do not alleviate the symptoms of nettle rash for long, they merely temporarily cool the skin. The poisons injected by the trichomes are beneath the skin, untouched by the dock leaves. Why dock leaves then? Could it be that they are simply large, common and grow near Stinging Nettles?

The leaves and shoots of Stinging Nettle are edible, although not with the stings still intact! The stings are rendered impotent after heating or drying. The leaves can be used in soups. A Nettle Beer can be brewed from the plant. Stinging Nettle is rich in iron and minerals. The pendulant flowers are borne on separate sex plants. The stems are square.

Nettles like to grow in nitrogen-rich fertile pasture land where they can utilise the minerals. They are thus good for using as a compost, for - having absorbed the minerals - they will release them upon decay. In gardens nettles can be a rather persistent weed, returning season after season.

SILICON IN PLANTS It turns out that silicon seems to be an essential mineral for healthy growth of most plants, and yet the mineral silicon is, paradoxically, not included in commonly used fertiliser or nutrient solutions. Silicon seems to decrease the susceptibility of plants to fungal diseases. Although sandy soils are rich in non-soluble silicon, soluble silicon is usually very low. Usually present in plants at about 1%, some plants contain as much as 10% (by dried weight) of silicon. As a general rule of thumb, the monocotyledons like grasses and cereals are silicon accumulators, whereas most dicotyledons are non-accumulators. Silicon is abundant in soil as silicon dioxide, sand, but that is inert and insoluble and not available for direct uptake by the plant. And yet the plants are obtaining soluble silicon, usually as orthosilicate, somehow. Orthosilicates are created in the soil by chemical weathering of silicon-containing rocks (sandstone, granite, and quartz veins in limestone) and sandy soils (and not by wind or rain weathering which mostly produces smaller particles of sand). Some silicon may be released into the soil as monosilicic acid, Si(OH)4, Polysilicic Acids, and complexes with both organic and inorganic compounds. Monosilicic Acid is stable in neutral to weakly acidic soils, but rapidly polymerizes to polysilicic acids at higher pH when the concentrations of Monosilicic Acid are high, or in the presence of iron or aluminium oxides and hydroxides which are common in many soils. Although Monosilicic Acid is reactive, interacting with heavy metals, manganese iron and aluminium, Polysilicic Acid is chemically inert and just forms adsorbent colloidal particles in the soil. Available silicon in soil is poorly understood. Your author believes it is micro-organisms within the soil which is responsible for most of this chemical weathering of sand. There are millions of unknown microbes within soil which cannot be grown in culture; they have not been studied for this very reason. It only needs one of these microbes to chemically digest silicon dioxide to release it in soluble form. Some of these organisms must be responsible for most of the chemical weathering of grains of sand. If the reader doubts this, then ask yourself why lichen seems to only grow on rocks. As an instance, are lichens dissolving some nutrients held firmly in insoluble form within the rocks for use by themselves? The rock-dwelling lichens do actually dissolve and 'eat' the rocks they grow upon. As well as comprising the hollow needles of the stinging hairs in Stinging Nettles, silicon dioxide is also responsible for the sharp edges of some blades of grass: on those grasses that can cut like knives. Silicon dioxide is also used structurally within some plants, to help retain form. PHYTOLITHS and CYSTOLITHS Phytoliths, small distinctly-shaped particles of silicon dioxide, form in several plants. They are extremely resistant to change, being made of rocks. The shape of these phytoliths is unique to each plant species it grows in. The  phytoliths are often the only evidence left after the plant has long since decayed, and their shape is used to determine what, in the historical past, was being grown in any certain location. Older Nettle plants develop hard gritty deposits in the leaves called Cystoliths. In Nettles these contain silica (silicon dioxide) derived from the stinging hairs together with some magnesium-rich calcium carbonate. Your Author is uncertain whether researchers, when writing about phytoliths and cystoliths, actually mean the very same thing.

Some similarities to : Small Nettle, but that is about half as tall and has a much less hairier appearance. Also its flower catkins are much shorter, but the most important difference is that the male and female flowers on Stinging Nettles are on separate plants, whereas on Small Nettle they are on the same plant. The stems are square on both Nettles. There is another not as obvious difference: the roots of Small Nettle are white, whereas those of Stinging Nettle are a bright yellow/orange.

Stinging Nettle also produces the sterol β-Sitosterol).

Stinging Nettle plays host to the eggs of the Red Admiral Butterfly.