Andropogon gayanus Kunth, Poaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Risk assessment results: 

Australia: Reject, score: 8 (Go to the risk assessment)
Risk assessment from the Government of Queensland, Australia (PDF format).

Common name(s): [more details]

English: gamba grass, tambuki grass

Habit:  grass

Description:  "Tufted perennial; culms 150-250 cm high.  Leaf-blades linear, 20-60 cm x 4-20 mm, acuminate.  Racemes paired, terminal and axillary, 4-9 cm long; pedicels and internodes cuneate, clavate, ciliate.  Sessile spikelet 5-8 mm long; lower glume flat on the back with a median groove; awn geniculate, 10-30 mm long.  Pedicelled spikelet 5-8 mm long, with a short, straight awn"  (Renvoize, 1984; p. 281).

"Habit: Perennial; caespitose. Culms 150-250 cm long. Ligule an eciliate membrane. Collar without external ligule, or with external ligule. Leaf-blade base tapering to the midrib; without a false petiole, or with a false petiole. Leaf-blades 30-60 cm long; 4-20 mm wide. Inflorescence:  Synflorescence compound; paniculate; lax. Inflorescence composed of racemes; terminal and axillary; subtended by a spatheole. Spatheole lanceolate; 6-8 cm long; herbaceous. Racemes 2; paired; 4-9 cm long. Rhachis fragile at the nodes; glabrous on surface; ciliate on margins. Rhachis internodes cuneate. Rhachis internode tip transverse; crateriform; with simple rim. Spikelets appressed; in pairs. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster. Pedicels cuneate; 4-5 mm long; ciliate; tip lobed. Sterile spikelets: Companion sterile spikelets well-developed; male; elliptic; dorsally compressed; 5-8 mm long; as long as fertile. Companion sterile spikelet glumes chartaceous; glabrous, or pubescent, or villous; acute; awned; one glume awned, or both glumes awned; with 1-10 mm long awn. Companion sterile spikelet lemmas 2; enclosed by glumes. Fertile spikelets: Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets oblong; dorsally compressed; 5-8 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus oblong; 1 mm long; pilose; base obtuse; inserted. Glumes: Glumes dissimilar; exceeding apex of florets; firmer than fertile lemma. Lower glume oblong; 1 times length of spikelet; coriaceous; 2-keeled; keeled laterally. Lower glume intercarinal veins distinct. Lower glume surface flat and with a longitudinal median groove; glabrous. Upper glume lanceolate; chartaceous; 1-keeled. Upper glume muticous, or mucronate. Florets: Basal sterile florets barren; without significant palea. Lemma of lower sterile floret lanceolate; hyaline; 2 -veined. Fertile lemma oblong; hyaline; without keel. Lemma apex lobed; 2 -fid; awned; 1 -awned. Principal lemma awn from a sinus; geniculate; 10-30 mm long overall; with twisted column. Column of lemma awn glabrous" (GrassBase).

Habitat/ecology:  Favors monsoonal climates. Forms dense stands, excluding native species. Acts to modify fire regimes. In the Northern Territory, Australia, "it has invaded riparian vegetation (creek banks and flood-plain fringes), degraded areas, roadsides, pastures and Eucalyptus savanna, in areas where annual rainfall exceeds 600 mm" (Smith, 1995, cited in Csurhes & Edwards, 1998; p. 139). "A vigorous, robust grass which can form dense stands.  A highly productive grass that increases fuel loads, cures later than the native annual grasses and produces intense, late dry season fires which seriously damage native woody species." (Smith, 2002; p. 69).

Propagation:  "Intentionally spread as a pasture species.  Seeds also blown short distances and spread along roadsides by vehicles, e.g. in mud and on radiators, slashers and graders." (Smith, 2002; p. 69).

Native range:  Tropical Africa, introduced elsewhere.

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 invasive	Csurhes, S./Edwards, R. (1998) (p. 139)
Australia Australia (continental)	Queensland	introduced invasive	Smith, Nicholas M. (2002) (p. 69)

Comments:  Reported to be invasive in Venezuela (Csurhes & Edwards, 1998; p. 139).

Control: 

Physical:  Small patches may be dug out.

Chemical:  Spray with grass-selective herbicides (Weber, 2003; p. 45).

Additional information:
Information from the Purdue University NewCROP web site.
Fact sheet from the Government of Queensland, Australia. (PDF format)

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

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

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

References:

Clayton, W. D./Harman, K. T./Williamson, H. 2002. World Grass Species: Descriptions, Identification, and Information Retrieval (online resource).

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

Renvoize, S. A. 1984. The grasses of Bahia. Royal Botanic Gardens, Kew.

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

Snow, Neil/Lau, Alex. 2010. Notes on grasses (Poaceae) in Hawai‘i. In: Evenhuis, Neal L. and Eldredge, Lucias G., eds. Records of the Hawaii Biological Survey for 2008. Bishop Museum Occasional Papers 107:46-60.

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.