Juncus tenuis Willd., Juncaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Chinese: jian bei deng xin cao

English: field rush, path rush, slender rush, slender rush, slender yard rush, soft rush, wiregrass

French: jonc grêle

Habit:  rush

Description:  "Perennial herbs; stems 1-6 dm long, 1-2 mm in diameter, loosely cespitose.  Leaves basal, numerous and crowded, blades variable in length, 7-30 cm long, 1-1.3 mm wide, sheaths loose with wide hyaline margins prolonged into white scarious auricles up to 5 mm long.  Flowers (3-) numerous, borne singly on 1 side of rachis, in relatively compact dichasial cymes 1-7 cm long, forming less than 1/3 of plant, bracts 2-3, foliaceous, usually far exceeding inflorescence, each flower subtended by 2 bracteoles, these hyaline, triangular-ovate; perianth parts greenish, lanceolate, 3-4.5 mm long, apex long-acuminate, outer ones slightly reflexed at apex, inner ones with wide hyaline margins below; stamens 6, 1/2 as long as perianth; anthers shorter than filaments.  Capsules reddish brown, 1-celled, broadly ovoid, thin-walled, slightly beaked, 2/3 to rarely scarcely shorter than perianth.  Seeds pale brown, oblong, 0.3-0.4 mm long, slightly apiculate at both ends"  (Wagner et al., 1999; p. 1454).

Habitat/ecology:  In Hawai‘i, "naturalized in usually wet sites along trails, disturbed places, and pastures, 700-2,000 m"  (Wagner et al., 1999; p. 1454).

Propagation:  Seed

Native range:  North and South America, Europe, Asia and Australia (Wagner et al., 1999; p. 1454).

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	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1454)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1454)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1454) East Maui
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1454)

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)		Hafliger, E. (1092) (p. 81)
Canada Province of British Columbia	Canada (British Columbia)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
China China	China (People's Republic of)		Hafliger, E. (1092) (p. 81)
Colombia Colombia	Colombia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Costa Rica Costa Rica	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Ecuador (Mainland) Ecuador	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Guatemala Guatemala	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Honduras Honduras	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 200)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 191) var. anthelatus Wiegand and var. nakaii Satake
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Healy, A. J./Edgar, E. (1980) (pp. 92-93) "Widely occurring, occasional to locally abundant in dry to damp sites, sea-level to over 1000 m".
Perú Perú	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
United States (west coast) United States (west coast states)	USA (Oregon)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
United States (west coast) United States (west coast states)	USA (Washington)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

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

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

Taxonomic information about Juncus tenuis 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.

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.

U. S. Government. 2011. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2011. 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).

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