Pacific Island Ecosystems at Risk (PIER)

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Najas graminea
Delile, Hydrocharitaceae
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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Chinese: cao ci zao

English: ricefield waternymph

Japanese: hossumo

Habit:  aquatic herb

Description:  "Monoecious, very slender, much branched, rooted, submerged, herbaceous, grass-like, bright green, 10 to 60 cm long; roots may become long, creeping in soft mud; adventitious roots form at nodes of stems; roots are of uniform diameter full length, tawny-orange color; leaves flat, acicular, acute, often densely tufted on short lateral shoots giving a plumose habit, 1.8 to 3.5 cm long and 0.7 to 1.5 mm wide, minutely serrate with 40 to 60 inconspicuous, sharp, yellowish-brown teeth on each margin, leaf widens at base to broad sheath with 1 to 2 auricles half-clasping stem; sheath 0.3 to 5 mm long, 2 to 4 mm in width with 10 to 30 spines either side; auricles mostly long, triangular, about 1/2 the total sheath length, apex acute, rarely acuminate or obtuse, entire, rarely lobed, bearing up to 10 prominent spines; flowers often 3 together in different stages, spathes absent in all flowers; anthers 4-celled, elliptical, rarely ovate to oblong, 1 mm long, 0.4 to 0.7 mm wide, pollen pale yellow and produced in abundance; stigmas 2; fruit 2 to 4 in axils of leaves of small shoots, ellipsoidal; seeds ovate, raphe conspicuous, 2 mm long, testa with 20 to 30 lengthwise rows of angulate aereoles"  (Holm et al., 1997; pp. 494, 497).

Description from Flora of North America.

Habitat/ecology:  "In Southeast Asia, the weed is found most frequently in shallow, stagnant freshwater ponds and ditches"  (Holm et al., 1997; p. 499).

Propagation:  Seeds and rooting of fragments (Holm et al., 1997; p. 499).

Native range:  Africa, Asia and Australia; naturalized elsewhere (GRIN).

Presence:

Pacific
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Papua New Guinea
Bismarck Archipelago
Bismarck Archipelago   Peekel, P. G. [translated by E. E. Henty] (1984) (p. 44)
Papua New Guinea
Papua New Guinea (eastern New Guinea Island)
Papua New Guinea (eastern New Guinea Island) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Philippines
Philippine Islands
Philippine Islands native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
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) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Western Australia
Australia
Australia (continental)
Northern Territory native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Cambodia
Cambodia
Cambodia (Kingdom of) probably native
Waterhouse, D. F. (1993) (pp. 67, 78)
China
China
China (People's Republic of) native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Ponds, paddy fields, usually in still or slow-moving water; below 1800 m. Anhui, Fujian, Guangdong, Guangxi, Hainan, Hebei, Henan, Hubei, Jiangsu, Liaoning, Sichuan, Yunnan, Zhejiang
Indonesia
Indonesia
Indonesia (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Japan
Japan
Japan (country) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Honshu, Kyushu, Shikoku
South Korea
South Korea
South Korea (Republic of)   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
Malaysia
Malaysia
Malaysia (country of) native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Taiwan
Taiwan Island
Taiwan Island native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Ponds, paddy fields, usually in still or slow-moving water; below 1800 m.
Thailand
Thailand
Thailand (Kingdom of) native
Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
United States (west coast)
United States (west coast states)
USA (California) introduced
invasive
Flora of North America Editorial Committee, eds. (2013)
Rice fields; 200 m.
Vietnam
Vietnam
Vietnam (Socialist Republic of) probably native
Waterhouse, D. F. (1993) (pp. 67, 78)

Control:  Information on control from the Mississippi State University Extension Service.


Need more info? Have questions? Comments? Information to contribute? Contact PIER! (pier@hear.org)

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This page was created on 26 JAN 2007 and was last updated on 18 AUG 2013.