Last updated: 11th November 2002

NETTLE, STINGING

Family: Urticaceae

Genus: Urtica

Species: dioica

Source: CSL

Contents

General Background
Details of Quality Characteristics
Current Production and Yields
Constraints upon Production
Markets and Market Potential
Other Information
Research
Useful Websites
BioMat Net
Contacts
References

General Background

For information, see:
A Natural History of Nettles by Keith G R Wheeler

Nettle occurs as a perennial plant in Europe and in the temperate zones of Asia and America. It is a dioecious plant growing 30-150cm tall. The plant has simple, opposite, sharply toothed leaves (5-10cm long) with persistent stipules and stinging trichomes. The hairs covering the stems and leaves are filled with fluid and break off when touched, leaving a sharp point like a small hypodermic needle that allows the fluid to enter the skin and cause blistering. The unpleasant compounds are thought to be a histamine and acetyl-choline.

Flowers on the pant are greenish and are borne in drooping clusters at the stem nodes. Flowers are unisexual, staminate, or pistillate or borne in separate infloresences or sometimes intermixed. Plants flower in late spring or early summer and seeds form by late August or early September. The fruit is a tiny hard-coated achene. In addition to growing from seed the plants are able to spread rhizomatously. Roots of the plant are yellow and much branched. The stems root at the nodes and erect shoots initiate in the spring.

Nettle is commonly found growing in rich soils in forest clearings, stream banks, old fields and waste places. It is adapted to a wide range of climatic conditions in Europe, growing conditions are ideally 600-800 day degrees to over 3,250 day degrees above a base of 5.5ºC.

In Europe this plant is widely used for its medicinal properties in treatment of disease and disorders. The plant has been introduced to cultivation due to the growing demand for raw material (leaves and rhizomes). Considering that the plantation of nettle can be established from cuttings there is potential to cultivate both male and female forms.

There are currently three recognised subspecies, Urtica dioica ssp. Dioica being the most common. The other two recognised subspecies are Urtica dioica ssp. gracilis and holosericea.

Details of Quality Characteristics

The nettle plant contains high quality fibre, with properties similar to flax and hemp, consisting up to 17% by weight of the plant. The fibre has remarkable high tensile strength, fineness, low specific weight and average length of 4m, this allows production of fine fabrics and technical applications. Fibre from the nettle plants has a cellulose content of 86.5%. High protein content of the crop may also be utilised in industrial applications.

Male and female plants vary in quality and composition. The content of polyphenolic acids both in leaves and rhizomes is higher in male plants, however the chemical composition of female polyphenolic acid tends to be more complex.

Female plants generally have higher content of assimilation pigments whereas male plants have higher flavonol and polyphenol acid contents, particularly at the beginning of flowering.

Six compounds which are found in aerial parts of nettle plants are caffeic acid, rutin (rutoside), quercetin, hyperin, isoquercitrin, lignan and beta-sitosterol.

Nettle is nutritionally high in vitamins A, C and D, also minerals iron, manganese, potassium and calcium. It contains 21-23% crude protein and 9-21% crude fibre.

As a feed component the quality of nettle plants is valuable. At the vegetative stage plants contain 4% protein and fibre, 50 microg/g carotene, 4 microg/g riboflavin and 10 microg/g vitamin E. By incorporating nettle into poultry feed it is possible to increase protein intake by 15-20% and vitamin intake by 60-70%, also green feed requirements can be reduced by 30%.

Current Production and Yields

Urtica diocia is currently the subject of scientific interest and development in the following countries through Europe; Austria, Germany, Finland and UK. The plant is a promising candidate for sustainable production of natural fibre, particularly in Germany and central Europe.

Generally male plants appear to produce slightly greater mass than the female plants. Production appears to be limited in the first growing season but by the second year of production dry matter yields may be expected to be around 6-9t/ha (around 17% fibre). Once established the plants will remain under successful cultivation for around ten years.

Crop maturity affects fibre quality and to achieve optimum yield and quality the plantation may have to be harvested more than once per year. The cycle from germination to seed production can be as short as six weeks in ideal conditions.

Nettle could be the answer to current problems in agriculture relating to over-fertilised soils, this plant thrives in such conditions on nitrogenous soils.

Constraints upon Production

The crop grows well as a weed, once it is established the plant is very competitive and difficult to control with herbicides, weed control should not be a problem. A greater problem is likely to be associated with disposing of the plant at the end of the cropping period. The crop should be easy to establish and manage, but will require a high level of nitrogenous fertiliser application to achieve high yields. Establishment costs are currently high and an important factor to be considered when growing nettles.

Although vegetative propagation with cuttings is simple the process is very labour intensive, particularly in the case of large scale production. Although the plants produce good fibre commercial extraction of fibre fine enough for high quality fibre has not yet been achieved. Mechanical extraction methods are currently available in Germany, these however have not yet produced a fibre fine enough for spinning.

Retting is the other major constraint to increased production of nettle plants, enzyme retting has been attempted but much care needs to be taken. Used in too high concentrations or for too long the cellulose begins to dissolve and the fibre strength is lowered. Important factors to be considered in this process are enzyme concentration, temperature, pH value and duration of treatment, all may have an effect on the fibre quality if not used correctly. Retting in water has been proven to be successful but is not always practical.

Markets and Market Potential

Nettle has a vast number of potential applications, most are similar to those of hemp and flax. Potential uses include fibre, protein, culinary, medicinal, culinary, biomass, oil, repellent and waterproofing. It was suggested in 2000 that stinging nettle is one of the most undervalued of economic plants with potential applications in a wide range of uses. If technical problems are solved the nettle has greatest potential for long fibre pulping and textile markets.

As a fibre source nettle is a useful alternative or complementary product to other natural fibres such as hemp, linen and cotton, they will play an increasing role in the next 5-7 years. It is thought that nettle fibre has was used to make thread and fabric as far back as 2000 years. Nettles are currently used in the production of a silky fabric known as ramie. The nettle fabric is currently available in some Italian fashion houses. Other applications for the fibre from the nettle plants include rope, cloth and paper.

Nettle has several medicinal properties; astringent, tonic, anti-asthmatic and diuretic. Across Europe it is also used for the treatment of gout, dropsy, rheumatism and for weight loss. Nettle roots are commonly used in hair products to treat eczema and dandruff along with helping to stimulate hair growth.

It is thought that along with the vast number of applications mentioned above the water extracts of nettle can also be used successfully to control angular leaf-spot of cucumber by 32-66%.

Other Information

Propagation of nettle can either take place by seed or vegetatively by divisions. Vegetative propagation is simple but labour intensive, it can be done using conventional cabbage planting machinery. Stocks should be grown in rich potting medium with regular fertilisation to ensure healthy nursery stock is produced. Alternatively seeds can be planted in late fall to allow for germination to take place the following spring or summer. Germination occurs at alternating temperatures of 25 and 15ºC following warm stratification and in the presence of light on seeds that were dry stored for 3 months. Harvest is currently more difficult for nettle plants than for hemp.

Information on cultivation of nettle crops is limited although it is thought that the plant prefers loose soil, preferably with a layer of organic matter to encourage growth. The plant is thought to be responsive to nitrogen and will require high phosphate levels for rapid growth rates. Once established the plant is very competitive and difficult to control with herbicides, so weed control should not be a problem.

Certain varieties, particularly the taller ones, are thought to be resistant in the most part to weeds and pests, thus lowering the use of chemicals during the growth period.

It is as yet unknown how potentially damaging pests and diseases are to the crop, it is currently the only host to 28 insect species and an important host to a further 18 species. There are also 14 reported diseases of the crop although the current threat is unknown.

Research

Attempts to improve agronomic aspects of the nettle crop are currently being undertaken, main areas include establishing a good crop, nutrition requirements, maintenance work and harvesting techniques. Processing techniques also need to be reviewed to become more effective, extraction, spinning and weaving are the key areas. Further information needs to be gathered relating to wear resistance, fineness of the fibre and also effects on the skin before products become more widely available.

Once production potential of nettle crops has been reviewed establishment from seed should form the primary basis for further research. Also weed control should be investigated to reduce growing and establishment costs of the crop.

Useful Websites
http://www.dmu.ac.uk/faculties/art_and_design/research/team/sting/index.jsp - STING (Sustainable Technology In Nettle Growing) Project

http://www.defra.gov.uk/farm/acu/fibres/fibres.htm - Industrial Crops: Fibres; includes regular updates on recent developments and the future. Also provides access
to useful related reports.

http://www.nettletex.com - Produce fibre nettle cuttings (Urtica dioica L.). Useful literature list.

BioMat Net

Nettle (Urtica dioica)

FAIR-CT98-9615 – Nettle – reintroduction of stinging nettle cultivation as a sustainable raw material for the production of fibres and cellulose

Crops for Textiles/Fabrics/Cordage

Crops for Paper/Pulp

National Activities - Hungary – Where does Biomass fit in Hungary?

FAIR-PL97-3784 – Optimisation of the production chain for high performance “light natural sandwich materials” (LNS) as a basis for scaling-up

Contacts

Peter Ruckenbauer, Hermann Bürstmayr, Anita Stürtz
Institute of Agrobiotechnology (IFA-Tulln)
Tulln, Austria
Tel: +43 2272 66 280-205
Email: pruck@ifa-tulln.ac.at or buerst@ifa-tulln.ac.at

Tara Luna
PO Box 447
East Glacier, MT 59434
tluna@3rivers.net

References