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 (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. (2011)
Philippines Philippine Islands	Philippine Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

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)	Northern Territory	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Australia Australia (continental)	Queensland	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Cambodia Cambodia	Cambodia (Kingdom of)	probably native	Waterhouse, D. F. (1993) (pp. 67, 78)
China China	China (People's Republic of)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
Ecuador (Mainland) Ecuador	Ecuador (Republic of) (continental)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
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)	probably native	Waterhouse, D. F. (1993) (pp. 67, 78)
Malaysia Malaysia	Malaysia (country of)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
Taiwan Taiwan	Taiwan Island		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
Thailand Thailand	Thailand (Kingdom of)	probably native	Waterhouse, D. F. (1993) (pp. 67, 78)
Thailand Thailand	Thailand (Kingdom of)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 498)
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.

Additional information:
Information and photos at the University of California Statewide Integrated Pest Management Project

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

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

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

References:

Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James. 1997. World weeds: natural histories and distribution. John Wiley & Sons. 1129 pp.

Peekel, P. G. [translated by E. E. Henty]. 1984. Flora of the Bismarck Archipelago for naturalists. Office of Forests, Division of Botany, Lae, Papua New Guinea. 638 pp. ISBN 9980-66-000-7.

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.

Waterhouse, D. F. 1993. The major arthropod pests and weeds of agriculture in Southeast Asia. The Australian Centre for International Agricultural Research, Canberra. 141 pp.

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