Echinochloa polystachya (Kunth) Hitchc., Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results: 

Australia:  Reject, score: 13 (Go to the risk assessment)
Risk assessment from the Government of Queensland, Australia (PDF format).

Other Latin names:  Oplismenus polystachyus Kunth.; Pseudechinolaena polystachya (H.B.K.) Stapf.

Common name(s): [more details]

English: aleman grass, carib grass, creeping rivergrass

Habit:  grass

Description:  "Culms coarse to 2 m high in flower, from a long creeping and rooting base, glabrous, except the nodes hispid with dense yellowish hairs; leaf-blades up to 2.5 cm broad, scabrid; racemes ascending, 3-6 cm long, densely hispid at the base; spikelets nearly sessile, plano-convex, about 5 mm long."  (Adams, 1972)An aquatic or semi-aquatic, perennial, stoloniferous grass.  Leaves flat, smooth, 20-60 cm long and 1-1.5 cm wide  (Csurhes and Edwards, 1998; pp. 156-157).

"Perennial grass with hygro habits, up to 3 m height, with decumbent culms, simple, cylindrical, with long internodes semi-glabrous, roots fasciculated, adventitious rooting may also be observed, leaves of somewhat red-purplish colour, limbs plains, long and acuminated" (Ecoport).

Description from GrassBase.

Habitat/ecology:  "Freshwater wetlands, riparian habitats.  A C₄ aquatic grass of floodplains and estuaries with a very high productivity.  The grass does not tolerate drought and frosts, and grows well in standing water.  It is adapted to wet and very wet soils, and to varying water levels.  The fast growing grass forms extensive monotypic stands on the lower levels of floodplains, crowding out native water plants and altering the vegetation structure.  It grows rapidly during floods and decays rapidly during water retreat, resulting in a high release of nutrients during the low water period.  This nutrient flush may affect water quality and reduce the oxygen content"  (Weber, 2003; p. 143).

"Spread vegetatively when pieces of stems and roots are distributed by floodwaters.  Seed production in Australia is generally thought to be poor." (Smith, 2002; p. 73).

Propagation:  "Spread vegetatively when pieces of stems and roots are distributed by floodwaters.  Seed production in Australia is generally thought to be poor." (Smith, 2002; p. 73).

Native range:  "A native of tropical and subtropical countries of America from southern USA to northern Argentina where it forms dense swards in seasonal swamps and on less wet ground" (Smith, 2002; p. 73).

Presence:

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	introduced cultivated	Csurhes, S./Edwards, R. (1998) (pp. 156-157)
Australia Australia (continental)	Northern Territory	introduced invasive cultivated	Smith, Nicholas M. (2002) (p. 73) Established as a weed on the Mary River.
Australia Australia (continental)	Queensland	introduced invasive cultivated	Csurhes, S./Edwards, R. (1998) (pp. 156-157)
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)
Honduras Honduras	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Nicaragua Nicaragua	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Panama Panama	Panama (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Perú Perú	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Comments:  A serious weed in Queensland, Australia (Smith, 2002; p. 73). Considered a high priority threat to northern Australia (Csurhes and Edwards, 1998; pp. 156-157).

Control:  "Scattered plants may be removed manually, larger stands treated with herbicide"  (Weber, 2003; p. 143).

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

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

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

References:

Adams, C. D. 1972. Flowering plants of Jamaica. University of the West Indies, Mona, Jamaica. 848 pp.

Csurhes, S./Edwards, R. 1998. Potential environmental weeds in Australia: Candidate species for preventative control. Canberra, Australia. Biodiversity Group, Environment Australia. 208 pp.

Smith, Nicholas M. 2002. Weeds of the wet/dry tropics of Australia - a field guide. Environment Centre NT, Inc. 112 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.