Digitaria bicornis (Lam.) Roem. & Schult., Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Chinese: yi ma tang

English: Asian crab grass, crab grass, large crab grass, southern crabgrass

Habit:  grass

Description:  "Annual, at first tufted, culms later decumbent, rooting at the nodes, forming loose mats; flowering culms ascendingly erect, up to 60 cm high.  Cataphylls absent.  Sheaths moderately pilose to glabrous.  Ligule 1-3.5 mm high, truncate, erose.  Blades linear, 2.5-13.5 (-23) cm by 2-9 mm, patent to ascending, soft, usually scabrous on both sides, glabrous but for some in the throat, rarely sparsely pilose.  Peduncle up to 40 cm long, glabrous.  Racemes 2-5 (-10), longest 3.5-14.5 cm long, digitate or in up to 3 whorls along an up to 5 cm long common axis.  Rachis winged, serrate, spicules at least 0.05 mm long, rarely with some setae at base ('rachiseta').  Abscission of pedicels truncate, Spikelets binate, usually heteromorph, the sessile one glabrous to slightly pubescent, the pedicelled one pubescent, to both pectinate and pubescent, lanceolate, 2.75-3.5 mm long; hairs smooth, acute.  Lower glume very variable, 0.15-0.4 (-0.75) mm long, from nearly absent to a triangular scale, acute to bifid.  Upper glume 1-2.75 mm long, 0.35-0.8 times as long as the spikelet, nerves 3, pubescent, hairs overtopping.  Sterile lemma as long as the spikelet, that of the sessile spikelet usually glabrous and equidistantly 7-nerved, to slightly pubescent and inequidistantly nerved (the pedicelled spikelet then always pectinate!), to pubescent and pectinate (spikelets then homomorphous), those of the pedicelled spikelet usually pubescent and inequidistantly nerved, pubescence usually mixed with bristles, these indistinct and appressed in youth, patent and protruding from the pubescence in fruit, rarely and then only the basal spikelets homomorphous, glabrous and equidistantly nerved (the whole raceme should therefore be inspected!); nerves usually smooth, the second nerves sometimes minutely serrulate towards the apex.  Fertile lemma slightly shorter than the spikelet, yellowish in fruit.  Anthers 0.5-0.6 mm long, purple.  Stigma purple"  (Veldkamp, 1973; pp. 30-32).

"Small grass with awnless spikelets in digitately arranged panicle branches" (Whistler, 1988; p. 50).

Description from GrassBase.

Habitat/ecology:  "In American Samoa and Samoa, "uncommon in disturbed places" (Whistler, 1988; p. 50).  "Waste places, often on sand, also along the shore and in the dunes, up to 2000 m in New Guinea, but to 2450 m in Assam." (Veldkamp, 1973; pp. 30-32)

Propagation:  Seed

Native range:  Tropics and subtropics, rare in Africa, throughout Malesia (Veldkamp, 1973; pp. 30-32).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
American Samoa Tutuila Islands	Tutuila Island		Whistler, W. A. (1988) (p. 50)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Agrigan (Agrihan) Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Voucher cited: Fosberg 31606 (US, BISH, POM, NY, L)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Guguan Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Guguan Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Voucher cited: Falanruw 1801 (US)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Pagan Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Pagan Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Voucher cited: Fosberg 31366 (US, BISH, POM)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Rota Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Saipan Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Tinian Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Tinian Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Vouchers cited: Hosaka 2836 (US, BISH, POM), Fosberg 24813 (US, BISH, POM)
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37) ?
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced invasive	Herrera, Katherine/Lorence, David H./Flynn, Timothy/Balick, Michael J. (2010) (p. 56) Naturalized
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Voucher cited: Hatusima 10922 (FU)
Federated States of Micronesia Yap Islands	Yap (Waqab) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Federated States of Micronesia Yap Islands	Yap (Waqab) Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Voucher cited: Hosaka 3297 (US, BISH, POM, NY)
Guam Guam Island	Guam Island	introduced	Raulerson, L. (2006) (p. 8)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 50) West Maui. Voucher cited: H. Oppenheimer H20816 (BISH)
Nauru Nauru Island	Nauru Island	introduced invasive	Thaman, R. R./Fosberg, F. R./Manner, H. I./Hassall, D. C. (1994) (p. 69) Voucher cited: Scully 152N (US?)
New Guinea (Indonesia and Papua New Guinea) New Guinea Island	New Guinea Island	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2011)
Palau Palau (main island group)	Babeldaob Island		Raulerson, L./Rinehart, A. F./Falanruw, M. C. (1996) (p. 21)
Palau Palau (main island group)	Ngerkebesang Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
Palau Palau (main island group)	Ngerkebesang Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Voucher cited: Takamatsu 1867a (BISH)
Philippines Philippine Islands	Philippine Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Samoa Western Samoa Islands	Upolu Island		Whistler, W. A. (1988) (p. 50)
United States (other Pacific offshore islands) Wake Islands	Wake Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 37)
United States (other Pacific offshore islands) Wake Islands	Wake Island	introduced	Fosberg, F. R./Falanruw, M. V. C. (1980) (pp. 201-202) Vouchers cited: Fosberg 34936 (US), Brankamp in 1936 (BISH), Lyons 10 (BISH)

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)
China China	China (People's Republic of)	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2011) Waste ground, often on sand, including seashore sand; below 2000 m. Fujian, Hainan, Yunnan.
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Singapore Singapore	Singapore (Republic of)	native	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 34) Common
Thailand Thailand	Thailand (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Vietnam Vietnam	Vietnam (Socialist Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Seychelles Seychelles Islands	Agalega Island	native	Fosberg, F. R./Sachet, Marie-Hélène/Stoddart, D. R. (1983) (p. 132)

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

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

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

References:

Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. 2009. A checklist of the total vascular plant flora of Singapore: native, naturalised and cultivated species. Raffles Museum of Biodiversity Research, National University of Singapore. 273 pp.

Fosberg, F. R./Falanruw, M. V. C. 1980. Noteworthy Micronesian plants 4. Micronesica 16(2):201-210.

Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce. 1987. A geographical checklist of the Micronesian monocotyledonae. Micronesica 20:1-126.

Fosberg, F. R./Sachet, Marie-Hélène/Stoddart, D. R. 1983. List of the recorded vascular flora of Agalega. In: Sachet, M. H., D. R. Stoddart, and F. R. Fosberg. Floristics and ecology of Western Indian Ocean islands. Atoll Research Bulletin No. 273. Smithsonian Institution, Washington. 253 pp.

Herrera, Katherine/Lorence, David H./Flynn, Timothy/Balick, Michael J. 2010. Checklist of the vascular plants of Pohnpei with local names and uses. Allertonia, in press. National Tropical Botanical Garden, Lawai, Hawai‘i. 146 pp.

Raulerson, L. 2006. Checklist of Plants of the Mariana Islands. University of Guam Herbarium Contribution 37:1-69. .

Raulerson, L./Rinehart, A. F./Falanruw, M. C. 1996. A botanical reconnaissance of the proposed Compact-impact road alignment on Babeldaob Island, Republic of Palau. U. of Guam Herbarium Cont. No. 32. 78 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.

Thaman, R. R./Fosberg, F. R./Manner, H. I./Hassall, D. C. 1994. The flora of Nauru. Smithsonian Institution, Washington. Atoll Research Bulletin 392:1-223.

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

Veldkamp, J. F. 1973. A revision of Digitaria Haller (Gramineae) in Malesia. Blumea 21(1).

Whistler, W. A. 1988. Checklist of the weed flora of western Polynesia. Technical Paper No. 194, South Pacific Commission, Noumea, New Caledonia. 69 pp.

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