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]

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

French: jonc à lier, jonc diffus, jonc épars

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:  "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	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		Hafliger, E. (1092) (p. 76)

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	U.S. Dept. Agr., Agr. Res. Serv. (2009)
Chile (continental) Chile	Chile (Republic of)		Hafliger, E. (1092) (p. 76)
China China	China (People's Republic of)		Hafliger, E. (1092) (p. 76)
Indonesia Indonesia	Indonesia (Republic of)		Hafliger, E. (1092) (p. 76)
Japan Japan	Japan (country)		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)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2009)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Healy, A. J./Edgar, E. (1980) (p. 95) "In damp pasture and wet places".

Control: 

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).

Additional information:
Information from the book "Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide" (Motooka et al., 2003). (PDF format).

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

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

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

References:

Hafliger, E. 1092. Monocot Weeds 3. CIBA-GEIGY Ltd., Basle, Switzerland. 132 pp. plus plates.

Healy, A. J./Edgar, E. 1980. Flora of New Zealand, Volume III: Adventive cyperaceous, petalous & spathaceous monocotyledons. Government Printer, Wellington, New Zealand. 220 pp.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

Imada, Clyde. 2007. New Hawaiian plant records for 2005-2006. In: Evenhuis, Neal L. and Eldredge, Lucias G., eds. Records of the Hawaii Biological Survey for 2006. Part 2: Notes. Bishop Museum Occasional Papers 96:34-41.

Motooka, Philip/Castro, Luisa/Nelson, Duane/Nagai, Guy/Ching, Lincoln. 2003. Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. 184 pp.

U. S. Government. 2009. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2009. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

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).