Urtica dioica L., Urticaceae

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Primarily a threat at high elevations?  no

Risk assessment results:  High risk; score: 16 (Hawaii-Pacific Weed Risk Assessment for Urtica dioica)

Other Latin names:  Urtica galeopsifolia Wierzb. ex Opiz; Urtica gracilis Aiton; Urtica holosericea Nutt.; Urtica lyallii S. Watson; Urtica tibetica W.T. Wang

Common name(s): [more details]

English: European nettle, common nettle, giant nettle, nettle, stinging nettle

Habit:  herb

Description:  "Herbs, perennial, rhizomatous, 5-30 dm. Stems simple or branched, erect or sprawling. Leaf blades elliptic, lanceolate, or narrowly to broadly ovate, 6-20 × 2-13 cm, base rounded to cordate, margins coarsely serrate, sometimes doubly serrate, apex acute or acuminate; cystoliths rounded. Inflorescences paniculate, pedunculate, elongate. Flowers unisexual, staminate and pistillate on same or different plants, staminate ascending, the pistillate lax or recurved. Pistillate flowers: outer tepals linear to narrowly spatulate or lanceolate, 0.8-1.2 mm, inner tepals ovate to broadly ovate, 1.4-1.8 × 1.1-1.3 mm. Achenes ovoid to broadly ovoid, 1-1.3(-1.4) × 0.7-0.9 mm." (JSTOR Global Plants)

"A perennial plant, it grows to a height of 2.5 m with a spread of 2 m. ¶The stem is erect, quadrangular and covered with stinging hairs; the leaves are opposite, heart shaped and acuminate, with deeply serrate margins; the flowers are green--the male flowers occurring in the leaf axils, and the female flowers occurring terminally--and appear in summer and autumn." (Encyclopaedia Botanica, pp. 1001-1002)

"Descriptions from some countries probably depend on the locally available subspecies, with U. dioica subsp. dioica being more common in Europe and U. dioica subsp. gracilis more prevalent in North America. The former subspecies is predominantly dioecious, has 'weak' stems, a sprawling, branching habit, and leaf blades and stems usually strongly hispid with stinging hairs on both leaf surfaces. The latter subspecies, by contrast, is mainly monoecious, with rigid, upright stems, and leaf blades and stems hairless but with stinging hairs only on the underside of the leaves (Bassett et al., 1977).
"All subspecies are erect with extensive, brightly yellow-coloured rhizome or stolon systems, stems to about 2 m tall, leaves in opposite pairs, broadly ovate to lanceolate with rounded or more or less cordate bases, leaf margins toothed, leaf tip acute or acuminate. Inflorescences are axillary, spike-like, many-flowered, flowers small, green and unisexual. In subsp. dioica, pistillate (female) and staminate (male) flowers are almost always on different plants, but in subsp. gracilis the two flower types are in separate clusters on the same plant. The fruits are achenes, and these are tiny and light and readily carried by the wind. For a detailed description of U. dioica, see Reaume (2010)." (CABI)

Habitat/ecology:  "A native of the temperate regions of Europe and Asia, it is adaptable to most soils and positions, and is drought and frost resistant." (Encyclopaedia Botanica, pp. 1001-1002)

"U. dioica occurs in a wide range of habitats, as a common understorey species of riparian communities, but also in or near marshes and meadows, including grazed pasture land (Carey, 1995; Popay et al., 1982). Bayer CropScience (2015) records the weed as present in pastures, nurseries, orchards, neglected yards, waste places, roadsides, flood plains, stream banks and ditches. It is also a common weed of disturbed areas, preferring to grow on deep rich, moist soils, being intolerant of poor fertility, dense shade and frequent disturbance. According to Olsen (1921), in Denmark it thrives in full light as well as in light shade, but does best in half-shade. The same author found that, in general, more vigorous plants grew in soils with higher nitrate content, supporting observations by others that the species commonly grows where soils are rich in nitrogen. In pastures it invades areas of bare, nutrient-rich ground caused by overgrazing, poaching, stock feeding, spoil deposition and bonfires (Natural England, 1999).
"The North American subspecies gracilis is reported by Bassett et al. (1974) as occurring in moist shady woodlands, thickets and mountain slopes, along streams and roadsides, and near fencerows, generally in deep rich soils, a description which matches the habitats of the European subspecies dioica well.
"Greig-Smith (1948) said that, at least in Britain, outside its native habitat of woodland, it is 'an almost universal follower of man, occurring on heaps of wood, metal, stones, earth and sand, along the foot of walls, around sheep and cattle yards and at the foot of stacks'. He adds that it occasionally appears as an epiphyte on willow (Salix spp.), ash (Fraxinus spp.), hornbeam (Carpinus spp.), oak (Quercus spp.) and poplar (Populus spp.). In Canada too, Bassett et al. (1977) note that subsp. gracilis is often associated with human habitation.
"In Britain, "U. dioica has been noted as favouring areas which have been cleared of other invasive weeds; Lockton and Godfrey (2015) reported "U. dioica invading areas which have been subjected to eradication programmes for Japanese knotweed (Fallopia japonica) and Himalayan balsam (Impatiensglandulifera), while Cadbury (1976) also reported it in areas from which bracken (Pteridiumaquilinum) had been cleared." (CABI)

"U. dioica is often found in very large patches and forms pure stands under favourable conditions (Taylor, 2009). These patches are often the product of a single individual that has spread by rhizomes which can be 50 cm or more in length (Greig-Smith, 1948)." (CABI)

Propagation:  In cultivation (apparently): "Propagation is by seed." (Encyclopaedia Botanica, pp. 1001-1002)

"According to Bayer CropScience (2015), stands of U. dioica can persist for around 50 years, and Bassett et al. (1977) also suggest a conservative estimate of the age of some clones of at least 50 years.
"Taylor (2009) quotes Thompson and Grime (1979) in saying the seed bank of U. dioica is of the persistent type: few seeds germinate immediately after dispersal and the seed bank changes little in size during the season and is large in relation to the annual production of seeds. Wheeler (1981, cited by Taylor, 2009) found a seed bank which varied between 1754 to 9090 viable seeds m-2 in floodplain pasture. Roberts and Bodrell (1984) sowed seeds of U. dioica into sterilized soil in pots. The soil was periodically cultivated, and seedlings continued to emerge for 5 years, with peak seasonal emergence in April, and the greatest number emerging in the first year." (CABI)

"U. dioica is often found in very large patches and forms pure stands under favourable conditions (Taylor, 2009). These patches are often the product of a single individual that has spread by rhizomes which can be 50 cm or more in length (Greig-Smith, 1948)." (CABI)

Native range:  The native range of Urtica dioica L. (Urticaceae) includes northern Africa; parts of temperate and tropical Asia; Europe; Canada; Mexico; and the United States. (GRIN)

Impacts and invaded habitats:  Economic impact: "U. dioica is generally regarded as a weedy invasive species. Where it occurs in pastures and grasslands its monospecific clumps can take up considerable space and thus reduce hay yields and the amount of grass available to livestock. It is normally avoided by livestock, thus restricting their free movement. Although considered native to Canada, it is listed as a noxious weed in several provinces (Carey, 1995), including Nova Scotia and Quebec (Darbyshire, 2003) and Alberta and Manitoba (Bassett et al., 1977). In the USA, U. dioica is classed as weedy or invasive depending on state and authority (USDA-NRCS, 2015). According to Bayer CropScience (2015), it is a weed of cereal and other field crops, is difficult to eradicate and is an important alternative host of the economically damaging carrot fly (Psila rosae)." (CABI)

Impact on biodiversity: "The weediness of U. dioica is attributed to its spread by rhizomes, allowing it to form dense colonies that exclude other plant species (Bayer CropScience, 2015). Where U. dioica occurs in dense patches in pasture or woodland it could be a problem if it interferes with the growth or occurrence of endangered species." (CABI)

Social impact: "Generations of children and adults have suffered the stinging hairs of U. dioica subsp. dioica. A number of toxins are present in the stinging hairs, including serotonin and acetylcholine (Connor, 1977). A report in 1982 (Anon., 1982), cited by CBIF (2015), noted that hunting dogs in the USA were poisoned after massive exposure to stinging nettles. Symptoms included trembling, pain, slobbering, dyspnoea and vomiting. Without treatment some dogs died 2-3 days after exposure. The action of the stinging hairs is neutralized by heat or by drying, so leaves can be used for edible purposes quite safely (PFAF, 2015).
"The copious wind-blown pollen of U. dioica is a major contributor to summer hay fever (Hyde, 1959; Bassett et al., 1977)." (CABI)

"Although Urtica dioica is distributed widely in many parts of the world, it is considered invasive because of its nuisance value even within its native range, particularly in waste places, especially since its stinging hairs can cause painful welts on human and possibly animal skin. In some circumstances it can be very hard to eradicate because of its large root mass which allows it to spread vegetatively once it has established. In some countries it invades and takes up space in grassland, where it can form very large, often monospecific patches, and it can also be a nuisance in urban areas, especially in nitrogen-rich habitats." (CABI)

If you know of other invaded habitats or impacts of Urtica dioica, please let us know.

Presence:

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Asia Asia	Asia (temperate)	native	U.S. National Plant Germplasm System (year unknown) see ref for country details
Asia Asia	Asia (tropical)	native	U.S. National Plant Germplasm System (year unknown) see ref for country details
Asia Asia	Iran		Randall, R. P. (2017)
Asia Asia	Pakistan		Randall, R. P. (2017)
Asia Asia	Russia		Randall, R. P. (2017)
Australia Australia	Australia	invasive cultivated	Randall, R. P. (2017)
Japan Japan	Japan		Randall, R. P. (2017)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. National Plant Germplasm System (year unknown) see ref for regional details
Mexico Mexico	Mexico (United Mexican States)	invasive	Randall, R. P. (2017)
New Zealand New Zealand	New Zealand (country)	invasive	Randall, R. P. (2017)
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	invasive	Randall, R. P. (2017)
South America (Pacific rim) South America (Pacific rim)	Colombia		Randall, R. P. (2017)
South America (Pacific rim) South America (Pacific rim)	Ecuador		Randall, R. P. (2017)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Africa Africa	Africa (northern)	native	U.S. National Plant Germplasm System (year unknown) see ref for country details
Africa Africa	Egypt		Randall, R. P. (2017)
Africa Africa	Lesotho		Randall, R. P. (2017)
Arctic Sea Arctic Sea	Svalbard		Randall, R. P. (2017)
Canada Canada	Canada	native	U.S. National Plant Germplasm System (year unknown) see ref for regional details
Canada Canada	Canada	invasive cultivated	Randall, R. P. (2017)
Eurasia Eurasia	Georgia		Randall, R. P. (2017)
Eurasia Eurasia	Turkey		Randall, R. P. (2017)
Europe Europe	Austria		Randall, R. P. (2017)
Europe Europe	Belgium		Randall, R. P. (2017)
Europe Europe	Bosnia and Herzegovina		Randall, R. P. (2017)
Europe Europe	Croatia		Randall, R. P. (2017)
Europe Europe	Europe	native	U.S. National Plant Germplasm System (year unknown) see ref for country details
Europe Europe	Europe		Randall, R. P. (2017)
Europe Europe	Finland		Randall, R. P. (2017)
Europe Europe	France		Randall, R. P. (2017)
Europe Europe	Germany		Randall, R. P. (2017)
Europe Europe	Greece		Randall, R. P. (2017)
Europe Europe	Italy		Randall, R. P. (2017)
Europe Europe	Kosovo		Randall, R. P. (2017)
Europe Europe	Montenegro		Randall, R. P. (2017)
Europe Europe	Netherlands		Randall, R. P. (2017)
Europe Europe	Norway		Randall, R. P. (2017)
Europe Europe	Poland	cultivated	Randall, R. P. (2017)
Europe Europe	Romania		Randall, R. P. (2017)
Europe Europe	Serbia		Randall, R. P. (2017)
Europe Europe	Slovenia		Randall, R. P. (2017)
Europe Europe	Spain		Randall, R. P. (2017)
Europe Europe	Switzerland		Randall, R. P. (2017)
Europe Europe	United Kingdom		Randall, R. P. (2017)
Falkland Islands Falkland Islands	Falkland Islands		Randall, R. P. (2017)
Iceland Iceland	Iceland		Randall, R. P. (2017)
India India	India (Republic of)	invasive	Randall, R. P. (2017)
North America North America	Greenland		Randall, R. P. (2017)
North America North America	North America	invasive	Randall, R. P. (2017)
Northern Atlantic Region Northern Atlantic Region	Faroe Islands		Randall, R. P. (2017)
South Africa South Africa	South Africa (Republic of)		Randall, R. P. (2017)
South America South America	Argentina		Randall, R. P. (2017)
South America (non-Pacific rim) South America (non-Pacific rim)	Brazil		Randall, R. P. (2017)
South America (non-Pacific rim) South America (non-Pacific rim)	Uruguay		Randall, R. P. (2017)
United States of America United States	United States	native	U.S. National Plant Germplasm System (year unknown) see ref for regional details
United States of America United States	United States	invasive	Randall, R. P. (2017)
World World	Worldwide	introduced	U.S. National Plant Germplasm System (year unknown) "Naturalized (natzd. elsewhere)" (other than native areas [see this ref]; no other details provided)
World World	Worldwide	cultivated	Randall, R. P. (2017)
World World	Worldwide		CABI (year unknown) see CABI datasheet for more details about countries in which this species is native and to which it has been introduced, along with a brief "History of introduction and spread"

Comments:  As of 2014, not known from Hawaii. (CABI)

Risk of introduction: "U. dioica may easily be transported to countries where it is not yet present because it has long been used as a source of fibre, food and herbal medicines. It is also seen as a useful food source for many kinds of caterpillar and is sometimes deliberately planted for that purpose (for example, see the Monarch Butterfly New Zealand Trust (2015))." (CABI)

For more detailed information about Urtica dioica as a weed/invasive species, see the CABI datasheet on this species.

Control:  Prevention: "To prevent nettle infestations of grasslands, Natural England (1999) recommend avoiding the creation of bare ground and avoiding nutrient enrichment." (CABI)

Eradication: "According to Bayer CropScience (2015), eradicating an established stinging nettle colony is difficult because the extensive root system expands annually and cannot be suppressed by mowing, although cutting when the new shoots reach a height of 15-30 cm tall was recommended as a means of eradication by the UK Ministry of Agriculture and Fisheries in 1939." (CABI)

Control: "Non-chemical control measures for U. dioica are summarized by Bond et al. (2007)." (CABI)

Cultural control and sanitary measures: "Bayer CropScience (2015) claims that some control of nettles may be obtained through repeated tillage and cultivation over several years. Bassett et al. (1977), quoting Muenscher (1955), indicate that American stinging nettle will not survive repeated ploughing and mechanical cultivation; several years of such practices will effectively reduce infestations by destroying the extensive root systems." (CABI)

Physical/mechanical control: "Carey (1995) reported that U. dioica regenerates from its buried rhizomes and seeds relatively quickly after a fire, although its top growth is presumably severely damaged. Greig-Smith (1948) reported that the species will not withstand repeated cutting. Machines for pulling out grassland weeds have been developed and are seen as environmentally friendly alternatives to herbicide use. One such, developed in the late 1990s, is the Eco-Puller, a tractor-trailed and PTO-driven machine that pulls weeds from the ground in a way that mimics hand pulling. This is achieved by feeding tall plants between a pair of gripping rollers which then provide a good firm vertical pull which is necessary to get the root out of the ground. The weed gripping height is adjustable, but weeds should be at least 30 cm tall to be pulled effectively. Stinging nettle should be pulled early in the season as soon as the stems are robust (Natural England, 1999)." (CABI)

Biological control: "No biological control agents have been identified for this species and, since it is considered native to several continents, a search for such agents would probably not be practical." (CABI)

Chemical control: "Bassett et al. (1977) suggest that, in Canada, since there are no specifically recommended chemical control measures for the species, general control recommendations for perennial weeds in non-crop land will probably eradicate this plant. However, Popay et al. (1982) tested a number of herbicides commonly used for weed control and found that few gave complete control after a single application. Only 2,4-D + picloram or picloram granules were effective and, after a single application, nettle clumps were either completely killed or very few shoots emerged later and were killed by a repeat application a year after the first. Natural England (1999) also recommends clopyralid + triclopyr, 2,4-D + dicamba + mecoprop, fluroxypyr, mecoprop and triclopyr for effective nettle control." (CABI)

IPM: "In their evaluation of cutting as a control measure for U. dioica in a field used to corral cattle in Slovakia, Vozár et al. (2009) found that cutting every 5 weeks with or without removal of plant biomass reduced the dominance of nettles over the study period (2004-08). However, cutting every 5 weeks together with reseeding with the strongly competitive species Dactylis glomerata and Trifolium repens gave the best control." (CABI)

If you know of other control methods for Urtica dioica, please let us know.