Urtica urens L., Urticaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Chinese: ou qian ma

English: burning nettle, dog nettle, dwarf nettle, small nettle

French: ortie

Spanish: ortiga

Habit:  herb

Description:  "Taprooted annual herbs; stems erect or ascending, unbranched or branched from base, 10-60 (-80) cm long, glabrous or sparsely pubescent and with scattered, coarse, stinging hairs, hispidulous at nodes.  Leaves thin, elliptic to ovate, (2.5-) 4-13 cm long, (0.7-) 1.5-5.2 cm wide, often larger toward apex of stem, 3-5-nerved, glabrous except with scattered stinging hairs, margins coarsely laciniate-serrate, petioles 0.5-4.2 cm long, stipules oblong, 1-4 mm long.  Flowers in mixed clusters but predominantly pistillate, 0.5-2 (-2.5) cm long; pistillate calyx 1.5-2.5 mm long in fruit, ± sparsely hispid, margins hispid-ciliate.  Achenes deltoid, 1.5-2.5 mm long, smooth to slightly roughened with punctate dots"  (Wagner et al., 1999; p. 1314).

Description from Flora of North America online.
Description from Flora of China online.
Description from Flora of New Zealand online.

Habitat/ecology:  In Hawai‘i, "naturalized in pastures and subalpine forest, 790-2,290 m"  (Wagner et al., 1999; p. 1314).  In the continental U.S., "waste places, roadsides, pastures, barnyards, cultivated fields, rich woodlands; 0-700 m"  (Flora of North America online).  "Forest margins, roadsides, near villages; 500-1000 m in N China, 2800-2900 m in SW China"  (Flora of China online).  In New Zealand, "gardens, waste places, sheep camps and under trees, especially on farms, riverbeds, coastal cliffs and rough grassland"  (Webb et al., 1988; p. 1267).  "In Chile this species grows in the following environmental conditions:  Low altitude, interior valleys; coastal mountains, 500-2000 m; coastal areas, 0-500 m.  Watering conditions: Coastal fog/camanchaca: The plants obtain water mainly from condensation; extremely dry areas with very rare rainfall, the dry season lasts 8-12 months and in some years it is possible to have no rainfall at all, rainfall less than 100 mm/year; dry, arid areas, with long drought periods of 6-10 months, precipitations of 100 mm-300 mm. are concentrated in winter; somewhat dry areas where the drought may last 3-5 months, precipitations of 400-800 mm. are concentrated in winter; humid areas, with almost constant rainfall, short dry periods are possible (generally not longer than 1 month).  Light conditions: Fully exposed to the sun, level areas or slopes facing north; some shadow, some protection against direct sunlight, some shadow from vegetation, filtering about 20-40% of light; In shadow, steep slopes facing south or a vegetation cover which filters 40-80% of light; in deep shadow, deep ravines facing south with additional shadow from trees, or where there is a very dense vegetation cover which gives 80-100% shadow (for instance, the Valdivian forests); exposed, but with protection from direct sun through coastal fog (camanchaca)"  (Chileflora).

Propagation:  Seed

Native range:  "Eurasia, now a nearly cosmopolitan weed"  (Wagner et al., 1999; p. 1314).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Pacific offshore islands) Lord Howe Island	Lord Howe Island	introduced invasive	Australian Biological Resources Study (2011)
Australia (Pacific offshore islands) Norfolk Islands	Norfolk Island	introduced invasive	Australian Biological Resources Study (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 558)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 558)
Ecuador (Galápagos Islands) Santa Cruz Group	Santa Cruz Island	introduced	Charles Darwin Foundation (2008)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1314) Voucher cited: Rock 3169 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Herbarium Pacificum Staff (1996) (p. 7) Voucher cited: M. Hong s.n. (BISH)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Australia (continental)	introduced invasive	Australian Biological Resources Study (2011) All states except Northern Territories.
Australia Australia (continental)	New South Wales	introduced invasive	National Herbarium of New South Wales (2011) "Widespread weed".
Australia Australia (continental)	Queensland	introduced invasive	Australian Biological Resources Study (2011)
Canada Province of British Columbia	Canada (British Columbia)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)
Canada Canada	Canada (country)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)
Chile (continental) Chile	Chile (Republic of)	introduced invasive	Belov, Michail (2011)
China China	China (People's Republic of)	introduced invasive	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2011)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 181)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 1267)
United States (west coast) United States (west coast states)	USA (Oregon)	introduced invasive	Flora of North America Editorial Committee, eds. (2011)
United States (west coast) United States (west coast states)	USA (California)	introduced invasive	Flora of North America Editorial Committee, eds. (2011)
United States (west coast) United States (west coast states)	USA (Washington)	introduced invasive	Flora of North America Editorial Committee, eds. (2011)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)
United States (continental except west coast) United States (other states)	USA (Florida)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)

Additional information:
Photos and other information from Chileflora.

Additional online information about Urtica urens is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Urtica urens as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Urtica urens may be available from the Germplasm Resources Information Network (GRIN).

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Australian Biological Resources Study. 2011. Flora of Australia Online. Australian Biological Resources Study, Canberra.

Belov, Michail. 2011. Chileflora (online resource).

Charles Darwin Foundation. 2008. Database inventory of introduced plant species in the rural and urban zones of Galapagos. Charles Darwin Foundation, Galapagos, Ecuador.

Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido. 2006. Nouveau catalogue de la flore vaculaire de l'archipel Juan Fernández (Chile) [Nuevo catálogo de la flora vacular del Archipélago Juan Fernández (Chile)]. Acta Bot. Gallica 153(4):399-587.

Flora of North America Editorial Committee, eds. 2011. Flora of North America North of Mexico (online edition).

Herbarium Pacificum Staff. 1996. New Hawaiian pest plant records for 1995. In: Evenhuis, Neal L. and Miller, Scott, E., eds. Records of the Hawaii Biological Survey for 1995. Part 2: Notes. Bishop Museum Occasional Papers. 46:3-8.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

National Herbarium of New South Wales. 2011. PlantNet: New South Wales Flora online. The Plant Information Network System of the Botanic Gardens Trust Version 2.0. Online resource.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.

Zhengyi, Wu/Raven, Peter H./Deyuan, Hong. 2011. Flora of China (online resource).