Pacific Island Ecosystems at Risk (PIER)

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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 (2013)
Australia (Pacific offshore islands)
Norfolk Islands
Norfolk Island introduced
invasive
Australian Biological Resources Study (2013)
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 (2013)
All states except Northern Territories.
Australia
Australia (continental)
New South Wales introduced
invasive
National Herbarium of New South Wales (2013)
"Widespread weed".
Australia
Australia (continental)
Queensland introduced
invasive
Australian Biological Resources Study (2013)
Canada (British Colombia)
Province of British Columbia
Canada (British Columbia) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
Chile (continental)
Chile
Chile (Republic of) introduced
invasive
Belov, Michail (2013)
China
China
China (People's Republic of) introduced
invasive
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
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. (2013)
United States (west coast)
United States (west coast states)
USA (California) introduced
invasive
Flora of North America Editorial Committee, eds. (2013)
United States (west coast)
United States (west coast states)
USA (Washington) introduced
invasive
Flora of North America Editorial Committee, eds. (2013)
Also reported from
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Canada (except British Colombia)
Canada
Canada (country) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (continental except west coast)
United States (other states)
United States (other states) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (continental except west coast)
United States (other states)
USA (Florida) introduced
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)


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This page was created on 17 DEC 2010 and was last updated on 10 JAN 2011.