Nettles – What They Are And Why They Sting


Clumps of stinging nettles frequently grow in gardens and on wasteland, and most people will have had an unpleasant brush with them at some time. However, despite their vicious aspect, they are important weeds as they are nitrogen-rich and good for the soil.

There are over 2,600 species of nettles worldwide. Many are covered with hairs that sting. Each hair is filled with an irritant and when someone brushes up against it, the tip of the hair breaks, and the sting occurs.

Nettles are probably best known for their dense covering of stinging hairs, although individual plants may be completely devoid of these weapons. Each hair is a single, flask-shaped, hollow cell filled with an irritant fluid.

The tip of this cell is glass-like due to the presence of silica or lime compounds and is so brittle that it breaks easily. The jagged edges of the broken tip puncture the skin, and pressure on the softer base of the hair forces the fluid directly into the wound like a needle.

Clumps of nettles are common in the countryside, in hedges and ditches, in woods, or near buildings. They have a particular liking for rubble-strewn ground, and to grow well, they need nitrogen-rich soil. As a result, nettles are often found in farmyards and on wasteground such as building sites.

They are vigorous, invasive plants, and given ideal conditions, the tough, yellow roots branch repeatedly and spread through the surrounding soil. The lower parts of the stems may also sprawl and produce roots along their length, helping to establish the plants rapidly over a wide area.

Numerous tiny seeds are produced to colonize more distant habitats. Where conditions for growth are suitable, the plants are lush and may reach 150cm (5ft) in height. In poorer conditions, the plants are considerably smaller.

Stinging nettles

Stinging Nettles

There two most common nettle are the stinging or common nettle Urtica dioica, and the small nettle Urtica urens. They are very similar in appearance, but the small nettle is an annual, and is smaller than the perennial stinging nettle, reaching no more than 30cm (12in). Both species have heart-shaped, strongly-toothed leaves, usually dark, dusty green.

The small flowers are green and appear from May to September, forming long, slender, inconspicuous clusters which hang down from the base of each leaf stalk.

The male and female flowers of the stinging nettle do not come from the same plant, while those of the small nettle appear on the same plant. The nettle does not rely on insects to pollinate it, as pollen is dispersed by the stamens of the male flowers.

The male flowers remain bent over until maturity, when they suddenly straighten out and flick pollen into the air and onto nearby female flowers.

Barbed Leaves

Nettles are probably best known for their dense covering of stinging hairs, although individual plants may be completely devoid of these weapons. Each hair is a single, flask-shaped, hollow cell filled with an irritant fluid.

The tip of this cell is glass-like due to the presence of silica or lime compounds and is so brittle that it breaks easily. The jagged edges of the broken tip puncture the skin, and pressure on the softer base of the hair forces the fluid directly into the wound like a needle.

Different species of nettles produce different toxins. Some species produce formic acid and histamine, and the rash caused by the stings, with its accompanying itching or burning sensation, can last for an hour or two but also, in extreme cases, up to a day.

Stings and Remedies

Not surprisingly, most of the folklore of nettles concerns their power to sting and the cure for this. Roman soldiers were reported to have scourged themselves with nettles to combat the cold, wet conditions they encountered in Britain.

The tingling and burning sensation from the stings, and the resulting increased blood flow to the skin’s surface, drove away numbness. Belief in this remedy persisted for hundreds of years, and urtication, or thrashing the limbs with nettles, became an accepted treatment for arthritis and rheumatism.

There are several cures for nettle stings, but many still use a freshly picked dock leaf to wrap around the sting. This well-known treatment is certainly one of the most convenient since docks and nettles often grow alongside each other.

Docks are not the only plants to bring relief. Rosemary, mint, and sage are said to be equally efficacious. Some people also use the juice of the nettle to counteract the rash.

Caterpillar on nettle

Do Nettles Harm Wildlife?

Flies were believed to have an aversion to the plant, and bunches of nettles were sometimes hung around houses. Although flies are repelled by nettles, other insects are not. In summer, nettles attract large numbers of colorful butterflies. They do not feed on pollinated flowers but use the leaves to feed their larvae.

The caterpillars of the red admiral, peacock, and small tortoiseshell butterflies feed only on nettle leaves. The caterpillars of the painted lady and comma butterflies can feed on other plants, but nettles are their preferred food source.

Nettles are also important for birds as they feed on the butterfly’s larvae. Ladybirds also feed on the aphids that shelter among nettles.

However, while birds and insects don’t seem to get stung by nettles, other animals certainly do. Anyone with a dog knows the pain of seeing it suffer after brushing up against a stinging nettle, so be sure to keep them away.

Family Members

There are over 2,600 species of nettle, but not all of these sting. Pellitory-of-the-wall is a plant that is often found growing on walls or rocks. It has reddish stems and untoothed leaves and bears only a passing resemblance to other nettles.

It is widespread and grows on rocks, cliffs, and hedgerows. Although the plant flowers, it produces green blooms, like the stinging nettle.

Mind-your-own-business was introduced to Britain from the islands of the western Mediterranean as a garden plant and can now be found growing wild on banks and walls.

At first glance, it is difficult to imagine that this plant is a relative of the coarse, erect nettle. Its slender, creeping stems and tiny, rounded leaves form dense mats of delicate, bright, evergreen foliage. Neither this plant nor wall pellitory is armed with the stinging hairs of its relatives.

Several plants are frequently mistaken for nettles, even though they are not related in any way. There are the dead nettles, members of the mint family, Labiatae. They look very similar to true nettles until their large white or purple flowers appear. However, they lack stinging hairs, hence the general names of ‘dead’ or ‘blind’ nettles. It is thought that they evolved to look like nettles to keep away predators.

Uses of Nettles

Nettles have historically had many uses, some of which are not used anymore. The leaves and seeds were widely used in homeopathy and can still be found today.

They were mainly used as infusions in treating asthma, consumption, and other conditions. During WW2, nettles provided chlorophyll for the drug industry. They were also used in drinks like nettle tea or nettle beer, similar to ginger beer, and drunk to relieve rheumatic pains.

Nettles are still used as food for many animals. The whole plant is eaten in hay by cattle, as the wilted nettles do not sting. Nettle seeds fatten poultry, and boiled nettles can be fed to pigs. When treated like hemp or flax, nettle stems yield good fiber used mainly for coarse sailcloth.

The use of nettles dates back to prehistoric times. Bones from the Bronze Age have been found wrapped in nettle cloth. Tablecloths, bed linen, and a velvet-like material were also regularly made from nettles.

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