Despite its reputation as a garden menace, the stinging nettle provides a home for wildlife as well as having a host of beneficial properties
In neglected corners of gardens and fields thrive dense patches of one of nature’s best survivors, the stinging nettle. Growing tall and luxuriant, it can be the bane of the gardener, yet this verdant herbaceous perennial is one of the single most important native plants for sustaining wildlife in the British Isles.
Its armoured stems and leaves provide a safe home for the larvae of numerous butterflies and moths, and a hotel for a wide range of insects, including aphids. These, in turn, are food for other predators, from ladybird larvae to birds.
Nettles also have a myriad of applications in cookery and for health purposes. In addition, the tough fibres have been used to create yarn, rope and fabric for centuries.
There are more than 80 species of nettle worldwide, but only two are found in Britain. These are the perennial Urtica dioica, and the annual Urtica urens. U. dioica has male and female flowers on separate plants, while U. urens has flowers of both genders on one plant.
The wind-pollinated, greenish-white tasselled flowers with a cluster of four petals appear in May. Eventually they fade to amber or brown in September.
The leaves and stems of both varieties are a rich green, sometimes with the faintest hint of plum. They have serrated margins that grow like canines, becoming more prominent as the plant ages. Each leaf has a twin on the opposite side of the central stem, arranged in a spiral staircase formation so that all light below is blocked out. This is an evolutionary trick, called phenoplasticity. It ensures the plants, which can reach up to 6½ft (2m) high, shade out all the competition below.
Nettles grow in multiple conditions and locations, from cracks in paving slabs to hillsides 2,700ft (823m) high. However, flowering can be inhibited if the soil is poor or they are confined to deep shade. For these reasons, their ideal site has nitrogen-rich, moist soil on the edge of a pasture or stream.
The tough yellow nettle roots spread rapidly, attaching themselves to the soil at the nodes. These are buds which grow into aerial shoots just under the soil surface. New rhizomes are formed in later summer and autumn, and while frost and drought can restrict their growth, they will overwinter. The stems turn to a whitish-grey in winter and can decompose completely before emerging in spring. Both varieties spread in this way, and new plants will grow from the smallest root.
Nettles also reproduce via tiny green seeds, produced from September onwards.
U. urens puts out more seeds as it only lasts for one year. These germinate on bare soil warmed by sunlight, where they stay viable for up to five years. They will float on water for up to a week without being damaged. As well as being windblown, the seeds have bristly outer cases which can hook into the fur of passing animals. They can also be ingested by worms and extracted in worm casts.
New nettles appear from March, growing more quickly and strongly than surrounding weeds in order to stay above other vegetation.
It is the wild nettle’s name that highlights its most notable characteristic. Urtica comes from the Latin verb urere, meaning to burn, while the word nettle originates from the Anglo Saxon for needle. The plant has also been known as burn nettle or burn weed.
The sting is produced by hairs on the leaves. These are long glassy trichomes, single cells that are elongated to razor- sharp points. These trichomes are filled with silica, the material glass is made from. When under pressure, a swollen sac of liquid at the base is pushed up into the skin, like a syringe.
As brittle as fine glass, these hairs can break off into the skin, injecting concoctions of chemicals that cause a rash. This potion contains a combination of chemicals that include formic acid, histamine, which can trigger inflammation, serotonin and a neurotransmitter acetylcholine. There is
a fifth ingredient that is yet to be identified. How the cocktail works is currently unknown.
This jagged armour forms the perfect protection against grazing animals that might otherwise eat the plant. Research has shown that nettles in heavily grazed areas have more of the stinging spines.
A sheltered home
The spines do not just protect the plant, they provide one of the most undisturbed habitats on the planet for insects.
According to the Natural History Museum, more than 100 species of insect have been recorded feeding on nettles. These range from nettle weevils to aphids. Their small size means the insects are able to move between the spines without activating the sting.
The leaves are the primary food source for peacock, small tortoiseshell and red admiral caterpillars, which feed on nettles in large numbers. These larvae hide in silk webs at the top of the stems. Moths, such as the snout, the spectacle, the nettle tap and the mother of pearl, also lay their eggs on nettles.
With so many insects living on them, nettles provide a valuable food source for a host of predators, including damselflies and birds. These feed on the aphids, seeds and fresh spring growth. Blue tits can often be seen darting around the stems in summer. When the seeds are ripe, chiffchaffs, bullfinches and goldfinches
all feast on the plants.
Nettle leaves offer an arsenal of natural remedies for the garden. Rich in nitrogen, they are the perfect fuel for compost heaps. Here, if mixed thoroughly, they work as a natural activator, helping break down other plant materials. They are also useful as a sacrificial companion plant to vegetables crops, luring aphids away from other specimens.
Brewed up into a compost tea with water, they can be used as an organic plant food. To make the mixture, the leaves and stems, but not the seeds, are chopped up finely in a bucket. Rainwater is added and the bucket covered and left for two weeks.
The resulting brew is filtered through a sieve and diluted to one part to 10 parts water for use. It can be used as a plant spray for fungal infections as it contains natural anti-fungal properties, namely a compound called lectin agglutinin. Fruit packers have been known to add nettles to apple boxes to stop them going mouldy.
Far from being a pest to be destroyed at the earliest opportunity, the stinging nettle is a plant with a wide range of benefits, for both wildlife and people. A true survivor, it has earned its place in a quiet corner of garden or field.
Food and medicine
Over the centuries, all parts of the nutrient-rich nettle have been used for food and medicine. The root can be dried and used in tinctures, the stem and leaves made into soups or teas, and the seeds used for medicines. Nettles have astringent, expectorant, anti-inflammatory, haemostatic and diuretic properties.
Hippocrates and his followers found 61 remedies using nettles. Galen, a Greek physician in the Roman empire, recommended the plant for bites and wounds, bleeding, pneumonia, asthma and much more. In ancient Egypt, nettles were used for the relief of arthritis and rheumatism, with patients flogging themselves with the plants to stimulate circulation. This is a practice that continued into the Roman era. There are stories that Caesar’s troops whipped themselves with nettle leaves to keep warm.
In the 17th century, Samuel Pepys included a “very good” nettle porridge in his diary. Nettles featured regularly in the rural diet in the 19th century, with the tender, young tops used in soups, puddings, beer and wine. Today, nettle leaves make a tasty substitute for spinach, with the added benefit of more iron and vitamin C.
The nettles are used to wrap around Cornish Yarg cheese, giving it its unique white bloom and edible mushroom-flavoured rind. The leaves, which attract naturally occurring moulds, are brushed onto the cheese in concentric circles.
Leaves should always be harvested before the plants flower, as older leaves are thought to upset the urinary tract and may form bladder stones. The sting is lost once the nettles are cooked, frozen, or dried and rubbed through a sieve.