Cyperus difformis L., Cyperaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Cebuano: gilamhon

Chinese: yi xing suo cao

English: dirty-Dora, one-arm sedge, rice sedge, small-flower umbrella plant, smallflower umbrella sedge, variable flat sedge

Filipino: baki-baki

French: souchet difforme

Iloko: ballayang

Japanese: tamagayatsuri

Spanish: cortadera, juncia de agua, lleivun, tiña

Habit:  sedge

Description:  "A tufted, smooth, annual or infrequently perennial sedge, 10 to 75 cm high; stems rather weak or tender, triangular, slightly winged, smooth, 1 to 3 mm thick; roots numerous, fibrous, reddish; leaves linear, few, weak, rather abruptly acuminate, smooth or slightly rough at the top, usually shorter than the plant is high (often two-thirds of the height), 2 to 5 mm wide, sometimes reduced to sheaths; sheaths tubular united, the lower sheaths straw-colored to brown; inflorescence in dense, globose, umbellate heads, simple or compound, 8 to 15 mm across, with numerous (more than 40) stellately spreading spikelets, the inflorescence rather loose, simple or compound, subtended by one, two, three, or four, variable, leaf-like bracts which are contracted or spreading, one may be almost erect, up to 25 cm long; the umbel rays 1 to 5 cm long, some sessile, some long peduncled; spikelets linear to oblong-linear, compressed but slightly swollen, obtuse, 2.5 to 8 mm long, 1 to 1.25 mm wide, 10 to 30 flowered, remarkable for the numerous, very small (0.6 to 0.8 mm), almost orbicular, concave, very obtuse glumes which occur in two opposite rows, closely packed, at first a rich brown, dirty green, or blackish, but becoming variegated by their pale yellow or almost white margins, with a green keel; stamens one or two; style branches tree; achenes elliptic to slightly obovate, acutely subequally triangular, lightly pitted, shining, straw-colored, yellowish brown or pale brown, about 6 mm long.  This species may be distinguished by the dense, globose heads composed of many radiating spikelets and by the many small orbicular, obtuse glumes which are a rich brown at first but later become variegated by their pale yellow or almost white margins"  (Holm et al., 1977; p. 236).

"Annuals, tufted, glabrous; culms up to 50 cm tall, sharply trigonal; leaves shorter than culm; bracteal leaves (some of them) longer than inflorescence; inflorescence umbellate, of rays to 5 cm long; spikes subglobose, dense, about 1-1.3 cm in diameter; spikelets with reddish markings on light brown; glumes rounded at apex; achenes trigonal"  (Stone, 1970; p. 168).

Habitat/ecology:  Usually a weed of wet places (Stone, 1970; p. 168).  "The plant normally grows in flooded or in very moist soils.  It is primarily a weed of paddy or flooded rice.  It is frequently found in small pools, along rivers, canals, and streams, in open wet places, and in grassy swamps.  It grows best in rich, fertile soils, but can grow in poorer sandy or clay soils of unused lands or in fallow rice fields.  It...has been reported from sea level to 1,400 m in Indonesia" (Holm et al., 1977; pp. 236, 239).

In Hawai‘i, "naturalized in wet sites, beach parks, urban sites, cultivated fields, and along roadsides, 0-50 m"  (Wagner et al., 1999; pp. 1395-1396).  In Fiji, "a naturalized adventive, occurring near sea level in wet places in the open, in swamps and pastures, along roadsides, and often abundantly in rice fields" (Smith, 1979; pp. 251-252).

Propagation:  Seed.  "Having heavy seed production and massive seedling densities, the plant quickly covers the ground and becomes dominant.  In tropical areas the plant apparently can flower and produce seeds all year long provided sufficient soil moisture is present" (Holm et al., 1977; p. 239).

Native range:  "Widespread in Eurasia from southern Europe through India and China to Japan and Malesia, and also in Australia and the Pacific Islands" (Smith, 1979; pp. 251-252).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Northern Mariana Islands		Swarbrick, John T. (1997) (p. 90)
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island	introduced	Raulerson, L. (2006) (p. 13)
Cook Islands Northern Cook Islands	Manihiki Atoll		McCormack, Gerald (2013) ?
Cook Islands Northern Cook Islands	Nassau Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1985) (voucher ID: PTBG 41600) Taxon name on voucher: Cyperus difformis
Cook Islands Northern Cook Islands	Pukapuka Atoll		McCormack, Gerald (2013) ?
Cook Islands Northern Cook Islands	Rakahanga Atoll		McCormack, Gerald (2013) ?
Cook Islands Northern Cook Islands	Suwarrow (Taka) Atoll		McCormack, Gerald (2013) ?
Cook Islands Southern Cook Islands	Mangaia Island		McCormack, Gerald (2013)
Cook Islands Southern Cook Islands	Ma‘uke Island		McCormack, Gerald (2013)
Cook Islands Southern Cook Islands	Palmerston (Avarau) Island		McCormack, Gerald (2013) ?
Cook Islands Southern Cook Islands	Rarotonga Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1982) (voucher ID: PTBG 41599) Taxon name on voucher: Cyperus difformis
Federated States of Micronesia Chuuk Islands	Weno (Moen) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 66)
Federated States of Micronesia Kosrae Island	Kosrae Island	introduced invasive	Space, James C./Waterhouse, Barbara/Denslow, Julie S./Nelson, Duane/Waguk, Erick E. (2000) (p. Voucher specimen) Voucher: BMW 5747 (BISH, BRI, GUAM)
Federated States of Micronesia Kosrae Island	Kosrae Island	native	Lorence, David H./Flynn, Timothy (2010) (p. 7) Roadsides and wet areas.
Federated States of Micronesia Kosrae Island	Kosrae Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1997) (voucher ID: PTBG 24666) Taxon name on voucher: Cyperus difformis L.
Federated States of Micronesia Kosrae Island	Kosrae Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1997) (voucher ID: PTBG 24879) Taxon name on voucher: Cyperus difformis
Federated States of Micronesia Kosrae Island	Kosrae Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (2005) (voucher ID: PTBG 42636) Taxon name on voucher: Cyperus difformis
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 66)
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	native	Herrera, Katherine/Lorence, David H./Flynn, Timothy/Balick, Michael J. (2010) (p. 41) Voucher cited: L. Stemmermann 2918A (BISH)
Federated States of Micronesia Yap Islands	Yap (Waqab) Island		Swarbrick, John T. (1997) (p. 90)
Fiji Fiji Islands	Rambi Island	introduced invasive	Smith, Albert C. (1979) (pp. 251-252) Voucher cited: DA 5763
Fiji Fiji Islands	Vanua Levu Island	introduced invasive	Smith, Albert C. (1979) (pp. 251-252) Vouchers cited: Greenwood 479, DA 12045, Degener & Ordonez 14223
Fiji Fiji Islands	Viti Levu Island	introduced invasive	Smith, Albert C. (1979) (pp. 251-252) Vouchers cited: DA 94, DA 10557, DA 11873, DA 3831, DA 7527, DA 5663, DA 10573
French Polynesia Society Islands	Tahiti Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Voucher cited: J. Florence & W.R. Sykes 11437 (PAP) Adventice
Guam Guam Island	Guam Island	introduced invasive	Stone, Benjamin C. (1970) (p. 168) Vouchers cited: Stone 4447 (GUAM), G.E.S. 45, G.E.S. 236, Moore 144, Fosberg 35566, Rodin 764
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 66)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 1395-1396)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Starr, Forest/Martz, Kim/Loope, Lloyd L. (2002) (pp. 19-20) West Maui. Voucher cited: Starr & Martz 990724-1 (BISH) Common
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 35) East Maui. Voucher cited: Starr & Starr 030807-3 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 1395-1396) Voucher cited: Heller 2003 (BISH)
Japan (offshore islands) Ogasawara (Bonin) Islands	Bonin (Ogasawara) Islands		Kato, Hidetoshi (2007)
Marshall Islands Ralik Chain	Kili (Kõle) Atoll	introduced invasive	Vander Velde, Nancy/Vander Velde, Brian (2006) (p. 2) "Rare; small patch alongside ocean road, just north of town".
Marshall Islands Ratak Chain	Majuro (Mãjro) Atoll	introduced	Vander Velde, Nancy (2003) (p. 37) Rare
Palau Palau (Belau ) (main island group)	Babeldaob Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 66)
Palau Palau (Belau ) (main island group)	Babeldaob Island		Beleu National Museum (Republic of Palau. Koror.) (1976) (voucher ID: BNM 1157) Taxon name on voucher: Cyperus difformis L.
Palau Palau (Belau ) (main island group)	Malakal (Ngemelachel) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 66)
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. (2013)
Philippines Philippine Islands	Philippine Islands	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
Philippines Philippine Islands	Philippine Islands		Merrill, Elmer D. (1925) (p. 104) In open wet places, ascending to 2,000 m; a characteristic rice-paddy weed.
Solomon Islands Solomon Islands	Solomon Islands		Swarbrick, John T. (1997) (p. 90)
Solomon Islands Solomon Islands	Solomon Islands	native	Hancock, I. R./Henderson, C. P. (1988) (p. 62)

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)	New South Wales	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Australia Australia (continental)	Australia (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) South Australia, Victoria, Western Australia
Australia Australia (continental)	Northern Territory	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Australia Australia (continental)	Queensland	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Cambodia Cambodia	Cambodia (Kingdom of)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
Central America Central America (Pacific rim)	Costa Rica (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Central America Central America (Pacific rim)	Nicaragua (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Central America Central America (Pacific rim)	Panama (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
China China	China (People's Republic of)	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Grasslands at mountain slopes, shallow water, water margins, lake margins, wet places in grasslands, along trails, paddy fields; below 100-2000 m. Anhui, Chongqing, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Yunnan, Zhejiang.
China China	Hong Kong	native	Wu, Te-lin (2001) (p. 309) In wet grassland and along streams.
Indonesia Indonesia	Indonesia (Republic of)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
Japan Japan	Japan	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Japan Ryukyu Islands	Ryukyu Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
North Korea North Korea	North Korea (Democratic People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South Korea South Korea	South Korea (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Malaysia Malaysia	Malaysia (country of)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
Mexico Mexico	Mexico (United Mexican States)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Negara Brunei Darussalam Brunei	Brunei (Negara Brunei Darussalam)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
Singapore Singapore	Singapore (Republic of)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
Singapore Singapore	Singapore (Republic of)	uncertain if introduced invasive	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 31) Weed of uncertain origin
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	introduced invasive	Belov, Michail (2013)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Taiwan Taiwan Island	Taiwan Island	native	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Grasslands at mountain slopes, shallow water, water margins, lake margins, wet places in grasslands, along trails, paddy fields; below 100-2000 m.
Thailand Thailand	Thailand (Kingdom of)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)
United States (west coast) United States (west coast states)	USA (Oregon)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (California)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Vietnam Vietnam	Vietnam (Socialist Republic of)	probably native	Waterhouse, D. F. (1993) (pp. 64, 77)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
British Indian Ocean Territory Chagos Archipelago	Diego Garcia Island		Topp, J. M. W. (1988) (p. 18)
British Indian Ocean Territory Chagos Archipelago	Diego Garcia Island	introduced invasive	Whistler, W. Arthur (1996) (p. 23)
British Indian Ocean Territory Chagos Archipelago	Diego Garcia Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1995) (voucher ID: PTBG 23870) Taxon name on voucher: Cyperus difformis
Comoros Comoro Islands	Comoro Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
La Réunion (France) La Réunion Island	La Réunion Island	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 114)
Seychelles Seychelles Islands	Seychelles Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (continental except west coast) United States (other states)	USA (Florida)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized

Control:  If you know of control methods for Cyperus difformis, please let us know.