Urochloa decumbens (Stapf) R.D. Webster, Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 10 (Go to the risk assessment)

Other Latin names:  Brachiaria decumbens Stapf

Common name(s): [more details]

English: basalisk signal grass, Basilisk signal grass, common signalgrass, signal grass, Surinam grass

Spanish: braquiaria, pasto alambre, zacate Surinam

Habit:  grass

Description:  "Perennial to 1-1.5-(2) m tall; sometimes with short rhizomes; culms geniculate and rooting at the lower nodes, those internodes relatively short and bearing short blades, branching from the lower and middle nodes, the internodes flattened, solid or the lower becoming hollow, glabrous, often pilose just below the nodes, the nodes glabrous. Sheaths compressed, shorter than the internodes on flowering culms, papillose-hirsute, ciliate, the collar glabrous or sparsely pubescent; ligule 0.8-2.0 mm long, the membrane 0.3-0.7 mm long, the cilia 0.5-1.3 mm long; blades 5-19 cm long, 1.0-1.89 cm wide, linear to linear-lanceolate, papillose-hirsute, acuminate, the base asymmetrical, rounded, the margin wrinkled, strongly serrate with uneven teeth, cartilaginous. Panicle 6-14 cm long; common rhachis 2-9 cm long, hirsute, ending in a rudimentary branch; racemes 2-4, 3-8 cm long, somewhat curved, the rhachis winged, c. 1.5 mm wide, often curved, prominently nerved, glabrous on the back or pubescent at the pedicels inconspicuous to 0.5 mm long. Spikelets 4.6-5.2 mm long, imbricate, strongly secund, solitary, 2-rowed, sparsely pilose, green or purplish, acute and short-apiculate; lower glume 1.8-2.4 mm long, the lower portion adnate to the pedicel for up to 0.2 mm, ovate, broadly acute, glabrous, 9-11-nerved, the nerves anastomosing, rhachilla between the glumes elongated; upper glume as long as the floret, broadly elliptic-ovate, 7-9-nerved, sparsely pilose toward the tip; lower floret staminate, the lemma as long as the upper floret, broadly elliptic-ovate, 5-nerved, the nerves connected with cross-veinlets at the tip, very sparsely pilose at the tip, the palea as long as the upper floret; upper floret 4.1-4.3 mm long, 1.9-2.0 mm wide, elliptic, acute, minutely pitted; anthers 2.5-3.0 mm long; stigmas purple" (Dassanayake, 1994; p. 86).

"Closely related to [U.] brizantha and often confused with that species outside its native range. [Urochloa] decumbens differs from [U.] brizantha primarily in its more broadly winged raceme rhachises and in its decumbent habitat with generally shorter leaf blades. Some of the selections that have been widely introduced as forage grasses could be of hybrid origin and identification is not always easy" (Dassanayake, 1994; p. 86).

Description from GrassBase.

Habitat/ecology:  (no habitat/ecology info known by PIER)

Propagation:  Seed

Native range:  Tropical Africa.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Galápagos Islands) Isabela Group	Isabela Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Isabela Group	Volcán Sierra Negra, Isabela Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) San Cristóbal Group	San Cristóbal Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Santa Cruz Group	Santa Cruz Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Fiji Fiji Islands	Vanua Levu Island	introduced cultivated	Smith, Albert C. (1979) (p. 328) See comment below. Voucher cited: DA L.13387
Fiji Fiji Islands	Viti Levu Island	introduced cultivated	Smith, Albert C. (1979) (p. 328) See comment below.
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 49) Voucher cited: L.W. Pratt 3341 (BISH)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 39) Misidentified as Brachiaria brizantha per Snow & Lau, 2010; p. 49. Voucher cited: Starr & Starr 040607-4 (BISH)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 49) Voucher cited: F. Starr & K. Starr 040607-4 (BISH)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 49) Vouchers cited: C. Trauernicht 208 & M. Clark (BISH), T. Flynn 7371 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced cultivated	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 39) Misidentified as Brachiaria brizantha per Snow & Lau, 2010; p. 49. Voucher cited: Joy HA-5222 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced cultivated	Snow, Neil/Lau, Alex (2010) (p. 49) Voucher cited: R. Joy s.n. (BISH 634161)
Solomon Islands Solomon Islands	Solomon Islands	introduced cultivated	Hancock, I. R./Henderson, C. P. (1988) (p. 52)

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)	Queensland	introduced invasive	Queensland Herbarium (2002) (p. 2) As Brachiaria decumbens

Comments:  Pasture trials in Fiji (Smith, 1979, p. 328). Present status not known.

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

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

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

References:

Charles Darwin Foundation. 2008. Database inventory of introduced plant species in the rural and urban zones of Galapagos. Charles Darwin Foundation, Galapagos, Ecuador.

Charles Darwin Research Station. 2005. CDRS Herbarium records.

Dassanayake, M. D., gen. ed. 1994. A revised handbook to the flora of Ceylon. Vol VIII. Amerind Pub. Co., New Delhi. 458 pp.

Hafliger, Ernst/Scholz, Hildemar. 1980. Grass weeds, vol. 1. CIBA-GEIGY Ltd., Basle, Switzerland. 142 pp. + plates.

Hancock, I. R./Henderson, C. P. 1988. Flora of the Solomon Islands. Research Bulletin No. 7. Ministry of Agriculture and Lands, Honiara. 203 pp.

Queensland Herbarium. 2002. Invasive Naturalised Plants in Southeast Queensland, alphabetical by genus. Modified from: Batianoff, George N. and Butler, Don W. (2002). Assessment of Invasive naturalized plants in south-east Queensland. Appendix. Plant Protection Quarterly 17, 27-34. 11 pp.

Smith, Albert C. 1979. Flora Vitiensis nova: a new flora of Fiji. National Tropical Botanical Garden, Lawai, Kauai, Hawaii. Volume 1. 494 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.

Starr, Forest/Starr, Kim/Loope, Lloyd L. 2006. New plant records from the Hawaiian Archipelago. In: Evenhuis, Neal L. and Eldredge, Lucias G., eds. Records of the Hawaii Biological Survey for 2004-2005. Part 1: Articles. Bishop Museum Occasional Papers 87:31-43.

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