Juncus effusus L., Juncaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  yes

Common name(s): [more details]

Chinese: deng xin cao

English: Japanese mat rush, common rush, lamp rush, soft rush

French: jonc à lier, jonc épars, jonc diffus

Spanish: junco de esteras, junquera

Habit:  rush

Description:  "Perennial herbs, rhizomes stout, covered with overlapping scales, roots thick; stems crowded along rhizome, reddish brown to purple at base, striate, terete, 4-8 dm long, pith solid.  Leaves basal, scale-like, bladeless, sheaths dark reddish brown to purple at base, paler toward apex.  Flowers numerous in usually contracted or sometimes more open, cymose inflorescences up to 8 cm long, appearing lateral, lowest bract terete, appearing to be a continuation of the stem, bracteoles 3, colorless, ca. 1/4 as long as perianth; perianth parts pale, rigid, narrow, not obscuring the capsule, outer ones ca. 2.5 mm long, inner ones ca. 2 mm long, about as long as capsule, apex long-acuminate; stamens 3; anthers and filaments about equal.  Capsules pale to medium brown, in contrast to the pale perianth, shiny, 3-celled, ovoid, apex truncate.  Seeds pale brown, ca. 0.5 mm long, ca. 3 times longer than wide"  (Wagner et al., 1999; p. 1453).

Habitat/ecology:  "Freshwater wetlands, wet grassland.  Where native, this plant is found in wet ground, cypress swamps, shores of ponds, marshes, bogs, riparian habitats, and damp woods.  It grows mostly on acid soils.  The species is a troublesome weed of pastures and also invades native communities.  The plant forms dense patches that suppress native species by shading them out, and becomes dominant over large areas.  Single tussocks collate into a continuous cover over time"  (Weber, 2003; p. 225).  "Displaces natives in wet forests and bogs"  (Motooka et al., 2003).

 In Hawai‘i, "cultivated and naturalized along margins of ponds and streams, in open boggy sites, and wet areas along trails, 1,000-2000 m"  (Wagner et al., 1999; p. 1453).

Propagation:  Seed

Native range:  "Widely distributed in temperate regions of both hemispheres" (Wagner et al., 1999; p. 1453).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1453)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Frohlich, Danielle/Lau, Alex (2012) (p. 40) Voucher cited: T. Flynn 7395 (BISH)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1453)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1453)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Imada, Clyde (2007) (p. 37) Voucher cited: L.M Crago, C. Imada & C. McGuire 2005-238 (BISH)
Philippines Philippine Islands	Philippine Islands		Merrill, Elmer D. (1925) (p. 201) In open swampy places, altitude 1,400 to 2,300 m.

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)	New South Wales	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalised
Australia Australia (continental)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) South Australia, Tasmania, Western Australia Naturalised
British Columbia (province of Canada) Province of British Columbia	Canada (British Columbia)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	El Salvador (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
China China	China (People's Republic of)	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Forest margins, wet grasslands, pools, morasses, lake margins, river banks, fields, rice fields; 200-3400 m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Shandong, Sichuan, Xizang, Yunnan, Zhejiang.
China China	Hong Kong	native	Wu, Te-lin (2001) (p. 306) In wet places.
Indonesia Indonesia	Indonesia (Republic of)		Hafliger, E. (1092) (p. 76)
Japan Japan	Japan		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 200)
South Korea South Korea	South Korea (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 200)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Healy, A. J./Edgar, E. (1980) (p. 95) "In damp pasture and wet places".
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Taiwan Taiwan Island	Taiwan Island	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Forest margins, wet grasslands, pools, morasses, lake margins, river banks, fields, rice fields; 200-3400 m.
United States (west coast) United States (west coast states)	USA (Oregon)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (Washington)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island	native	U.S. Dept. Agr., Agr. Res. Serv. (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 Canada	Canada	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (continental except west coast) United States (other states)	United States (other states)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (continental except west coast) United States (other states)	USA (Florida)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Control: 

Physical:  "Cutting at ground level reduces the vigour but a follow-up programme is necessary to treat regrowth and seedlings.  Continuous grazing can eliminate the plant from pastures"  (Weber, 2003; p. 225).

Chemical: "Difficult because of thick rhizomes and roots.  Susceptible to glyphosate at 1-1.5% product applied to foliage (Hank Oppenheimer, Maui Pine"  (Motooka et al., 2003).