Urtica dioica angustifolia are known for their small stinging hairs that inject irritating chemicals and cause a skin rash upon contact. Urtica dioica angustifolia have traditionally been used as a cooked green as well as in teas and ale. The fibers have also traditionally been used to make textiles, nets, and paper.
I. Appearance and Characteristics
Urtica dioica, often known as common nettle, burn nettle, stinging nettle (although not all plants of this species sting) or nettle leaf, or just a nettle or stinger, is a herbaceous perennial flowering plant in the family Urticaceae. Originally native to Europe, much of temperate Asia and western North Africa, it is now found worldwide. The species is divided into six subspecies, five of which have many hollow stinging hairs called trichomes on the leaves and stems, which act like hypodermic needles, injecting histamine and other chemicals that produce a stinging sensation upon contact (“contact urticaria”, a form of contact dermatitis).
Urtica dioica is a dioecious, herbaceous, perennial plant, 3 to 7 feet (0.9 to 2 metres) tall in the summer and dying down to the ground in winter. It has widely spreading rhizomes and stolons, which are bright yellow, as are the roots. The soft, green leaves are 1 to 6 inches (30 to 200 mm) long and are borne oppositely on an erect, wiry, green stem. The leaves have a strongly serrated margin, a cordate base, and an acuminate tip with a terminal leaf tooth longer than adjacent laterals. It bears small, greenish or brownish, numerous flowers in dense axillary inflorescences.
The leaves and stems are very hairy with non-stinging hairs, and in most subspecies, also bear many stinging hairs (trichomes or spicules), whose tips come off when touched, transforming the hair into a needle that can inject several chemicals causing a painful sting or paresthesia, giving the species its common names: stinging nettle, burn-nettle, burn-weed, or burn-hazel.
Nettles are the larval food plant for several species of butterflies, such as the peacock butterfly, comma (Polygonia c-album), and the small tortoiseshell. It is also eaten by the larvae of some moths including angle shades, buff ermine, 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).
It is a known host to the pathogenic fungus Phoma herbarum.
Stinging nettle is particularly found as an understory plant in wetter environments, but it is also found in meadows. Although nutritious, it is not widely eaten by either wildlife or livestock, presumably because of the sting. It spreads by abundant seeds and also by rhizomes, and is often able to survive and re-establish quickly after fire.
II. How to Grow and Care
Sunlight
Stinging nettle thrives in full sun conditions but will tolerate some shade. Too much shade makes the plant grow too tall and leggy.
Temperature and Humidity
Stinging nettle does well in all climate conditions across its hardiness range, USDA zones 4 to 10. It is more at home in humid climates but will grow adequately in dry atmospheric conditions, provided it has adequate soil moisture.
Watering
Stinging nettle has average water needs but will be especially vigorous in climates with frequent rainfall. Mature plants have a good tolerance for short periods of drought, but this is not a plant that does well in arid climates. If your region has regular rainfall (every two weeks or so), additional watering is not necessary.
Soil
This plant does best in evenly moist, loamy soils rich in nitrogen and phosphorus. It often thrives in disturbed soil, which is why it is often found growing in abandoned lots and building sites, provided the underlying soil is rich. It tolerates a wide range of pH levels, from very acidic to very alkaline. It does not do well in very dry, barren soils.
Fertilizing
Nettles thrive on nitrogen-rich soil, so periodic feeding with compost or a nitrogen-heavy fertilizer will help plants that are growing in poor, barren soil. But in most typical garden soil, stinging nettle does quite well with no feeding at all.
Pruning
Deadheading spent flowers will stop stinging nettle from spreading uncontrollably through self-seeding. Other than this, no pruning is necessary, other than pre-winter removal of dead stalks.
Propagation
Three cultivation techniques can be used for the stinging nettle: 1) direct sowing, 2) growing seedlings in nurseries with subsequent transplantation and 3) vegetative propagation via stolons or head cuttings.
- Direct sowing
The seedbed should have a loose and fine structure, but should be reconsolidated using a packer roller imminently prior to sowing. Sowing time can be either in autumn or in spring. Seed density should be 6 kilograms/hectare with row spacing of 30 cm (12 in) and 42–50 cm in autumn and spring, respectively. The disadvantage of direct sowing is that it usually leads to incomplete plant coverage. This drawback can be mitigated by covering the seedbed with a transparent perforated foil in order to improve seed germination. Further, weed control can be problematic as the stinging nettle has a slow seedling development time.
- Growing seedlings
For this technique pre-germinated seeds are sown between mid-/end-February and beginning of April and grown in nurseries. Seedlings are grown in tuffs with 3–5 plants/tuff and a seed density of 1.2–1.6 kg/1000 tuffs. Faster germination is achieved by alternating high temperature during daytime (30 °C for 8 h) and lower temperature during nighttime (20 °C for 16 h). Before transplanting, the seedlings should be fertilized and acclimated to cold temperatures. Transplantation should start around Mid-April with row spacing of 42–50 cm (17–20 in) and plant spacing within rows of 25–30 cm.
- Vegetative propagation
Stolons (with several buds) of 10 cm should be planted from mid-April in a depth of 5–7 cm (2–2+3⁄4 in). Head cuttings are grown in nurseries starting between mid-May and mid-June. Growing tips with two leaf pairs are cut from the mother plant and treated with root-growth inducing hormones. Transplantation can be delayed in comparison to the growing seedling technique.
Overwintering
No overwinter protection is needed for this hardy plant. Most gardeners will want to cut back dead stalks in late fall to prevent self-seeding in the garden.
III. Uses and Benefits
- Gardening uses
Nettles have a number of uses in the vegetable garden, including the potential for encouraging beneficial insects. Since nettles prefer to grow in phosphorus-rich and nitrogen rich soils that have recently been disturbed (and thus aerated), the growth of nettles is an indicator that an area has high fertility (especially phosphate and nitrate), and thus is an indicator to gardeners as to the quality of the soil.
Nettles contain nitrogenous compounds, so are used as a compost activator or can be used to make a liquid fertilizer, which although low in phosphate, is useful in supplying magnesium, sulphur, and iron. They are also one of the few plants that can tolerate, and flourish in, soils rich in poultry droppings.
The stinging nettle is the red admiral caterpillar’s primary host plant and can attract migrating red admiral butterflies to a garden. U. dioica can be a troubling weed, and mowing can increase plant density. Regular and persistent tilling will greatly reduce its numbers, and the use of herbicides such as 2,4-D and glyphosate are effective control measures.
- Medicinal uses
As Old English stiðe, nettle is one of the nine plants invoked in the pagan Anglo-Saxon Nine Herbs Charm, recorded in 10th-century traditional medicine. Nettle was believed to be a galactagogue – a substance that promotes lactation. Urtication, or flogging with nettles, is the process of deliberately applying stinging nettles to the skin to provoke inflammation. An agent thus used was considered to be a rubefacient (something that causes redness), used as a folk remedy for treating rheumatism. A study undertaken in 2000 showed that nettles were an effective therapy in relieving the pain of arthritis.
- Culinary uses
- dioica has a flavour similar to spinach when cooked. Young plants are harvested by many Native American communities and are cooked and eaten in spring when other food plants are scarce. Soaking stinging nettles in water or cooking removes the stinging chemicals from the plant, which allows them to be handled and eaten without injury. After the stinging nettle enters its flowering and seed-setting stages, the leaves develop gritty particles called cystoliths. Many sources claim consumption of these can irritate the kidneys and urinary tract; however, there is no medical evidence to support this claim. Cystoliths are made of calcium carbonate, and will not dissolve when boiled. Leaves harvested post-flowering must have their cystoliths broken down by acid, as in the fermentation process. In its peak season, nettle contains up to 25% protein, dry weight, which is high for a leafy green vegetable. The leaves are also dried and may then be used to make a herbal tea, as can also be done with the nettle’s flowers.
Nettles can be used in a variety of recipes, such as polenta, pesto, and purée. Nettle soup is a common use of the plant, particularly in Northern and Eastern Europe.
Nettles are sometimes used in cheesemaking, such as for Cornish Yarg and as a flavouring in varieties of Gouda.
Nettles are used in Montenegro, Serbia, North Macedonia and Bosnia and Herzegovina as part of the dough filling for the börek pastry. The top baby leaves are selected and simmered, and then mixed with other ingredients such as herbs and rice, before being used as a filling between dough layers. Similarly, in Greece the tender leaves are often used, after simmering, as a filling for hortopita, which is similar to spanakopita, but with wild greens rather than spinach for filling.
Young nettles can also be used to make an alcoholic drink.
- Other uses
Nettle fibre, stem, yarn, textile, jewellery with glass and nettle yarn
Nettle stems contain a bast fibre that has been traditionally used for the same purposes as linen and is produced by a similar retting process. Unlike cotton, nettles grow easily without pesticides. The fibres are coarser, however.
Historically, nettles have been used to make clothing for almost 3,000 years, as ancient nettle textiles from the Bronze Age have been found in Denmark. It is widely believed that German Army uniforms were almost all made from nettle during World War I due to a shortage of cotton, although there is little evidence to support this. More recently, companies in Austria, Germany, and Italy have started to produce commercial nettle textiles.
The fibre content in nettle shows a high variability and reaches from below 1% to 17%. Under middle-European conditions, stems yield typically between 45 and 55 dt / ha (decitons per hectare), which is comparable to flax stem yield. Due to the variable fibre content, the fibre yields vary between 0.2 and 7 dt / ha, but the yields are normally in the range between 2 and 4 dt / ha. Fibre varieties are normally cloning varieties and therefore planted from vegetative propagated plantlets. Direct seeding is possible, but leads to great heterogeneity in maturity.
Nettles may be used as a dye-stuff, producing yellow from the roots, or yellowish green from the leaves.
