Dwarf Nettle

Urtica urens L.

Family: Urticaceae.

Names:

Urtica is Latin for nettle.
Dwarf Nettle because it is smaller than most other nettles.

Other names:

English Stinging Nettle
Lesser Nettle
Lesser Stinging Nettle
Nettle
Small Nettle
Stinging Nettle

Summary:

Dwarf Nettle is an annual herb with square stems to 800 mm high with harsh stinging hairs. The leaves are opposite, with an egg-shaped blade 2-7 cm long and 1.5-5 cm wide, and clearly toothed. The separate male and female flowers are greenish and loosely clustered in the leaf axils. Each flower has 4 sepals (unequal in size in female flowers) but no petals, the male flowers have 4 stamens. The fruit is a tiny nut.
Native to Europe, it is now a weed of waste and cultivated land particularly in shady and fertile places. The hairs can produce redness of the skin and an intense itchiness. It flowers from July to December.

Description:

Cotyledons:

Two. Round to heart shaped. Tip indented. Edges rounded. Base tapered. Surface smooth and hairy. Petiole about the same length as the blade. Hairs on petiole.

First leaves:

Oval, lobed, paired, with scattered, stinging hairs emerging from "warts" on the leaf surface. Prominent veins.

Leaves:

Opposite and paired. 5-7 veined at the base. With rigid stinging hairs.
Stipules - Free from petiole, triangular, 1-2 mm long, 4 at each node between the petioles.
Petiole - 10-35 mm long. Hairy.
Blade - Egg shaped to oval, 20-70 mm long x 15-50 mm wide, deeply and regularly toothed. Tip pointed. Base tapered.

Stems:

Erect or upward bending, up to 800 mm long, covered in rigid stinging hairs. Four angled. Green and often with reddish purple stripes.

Flower head:

Clusters (racemes) in leaf axils, loose. Clusters shorter than the petioles. Male and female flowers in the same cluster.

Flowers:

Green, small, male and female flowers separate.
Ovary - Stigma almost stalkless, brush like.
Sepals - Female flower, 4, less than 1 mm long, 2 outer sepals smaller with a long stinging hair on their back. 2 inner sepals egg shaped, hairy on the outside edges, usually with a single outside stinging hair, or with sparse still hairs, enlarged to 2 mm long in fruit.
Male flower, 1-1.5 mm diameter, 4 equal sepals, concave, joined at the base.
Petals - None.
Stamens - of male flowers, 4, opposite the sepals.
Anthers -

Fruit:

Nut enclosed in persistent sepals. Flattened. Egg shaped 2 x 1.5 mm.

Seeds:

Small nut. Yellow to grey green. Shiny. Somewhat triangular pyramid in shape. About 2 mm long. Tip pointed. Edges smooth, flattish. Base flat to indented. Surface shiny.

Roots:

Key Characters:

Annual herb.
Leaves opposite, thin, regularly toothed, broad-ovate, 3-7 nerved from base with stinging hairs.
Stipules 1-2 mm long.
Flowers with sepals only.
Flowers in clustered axillary spikes.
Sepals 4.
Stamens 4
Adapted from J.M. Black, N.T. Burbidge and B.L. Rye.

Biology:

Life cycle:

Annual. Germinates from autumn to spring. Flowers from July to December.

Physiology:

Reproduction:

By seed.

Flowering times:

Spring to early summer in western NSW.
July to December in SA.
July to October in Perth.
Winter to spring in WA.

Seed Biology and Germination:

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

North Africa. Eurasia. Almost cosmopolitan.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Shaded areas or heavily grazed pastures.

Climate:

Tolerant of a wide range of environments.

Soil:

Tolerant of a wide range soil types. Prefers highly fertile areas.

Plant Associations:

Significance:

Beneficial:

A highly acclaimed boiled vegetable or soup.

Detrimental:

Weed of gardens, vegetables, pasture, stock yards, orchards, plantations, woodlands and disturbed areas.
Unpalatable and usually avoided by all animals.

Toxicity:

Contact causes a reddening of the area with itching, followed by swelling then an intense burning sensation on the skin in people. In most it soon passes but it may last up to 36 hours or longer.
Not recorded as toxic to stock. Cattle occasionally eat them with no apparent effect.

Treatment:

Rub an acidic solution on the contact area. Dock leaves are useful for this in the field.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Prevent seed set for several years.
Manual removal is difficult because the leaves and stems have stinging hairs. Isolated plants can be dug up with a fork or cultivator. Mowing is only effective if repeated regularly and is low enough to remove all flowers from July to December.
Grazing is not very effective.
For spot spraying use a mixture of 100 mL glyphosate(450g/L) plus 1 mL Hammer® in 10 L water. Apply in autumn or winter before flowering. A repeat application may be required to control plants that germinate after spraying.
4 L/ha of 2,4-DB with wetting agent can be used in bushland for more selective control. Apply annually in June and repeat in September.

Herbicide resistance:

Biological Control:

Related plants:

Stinging Nettle (Urtica dioica) is only in NSW.
Scrub Nettle (Urtica incisa) is a darker green perennial plant with larger, darker green leaves, 50-120 mm long which are more broadly toothed. It has more conspicuous flower sprays with male and female flowers usually on separate plants.

Plants of similar appearance:

Fat Hen (Chenopodium album) differs in its alternate leaves and absence of stinging hairs.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P233-234. Photos.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P261. Diagrams.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P143.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P210-211. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P734-745.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P228-229. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1251.3.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P72.

Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P119. Diagrams. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.