Panicum repens L., Poaceae

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Present on Pacific Islands?  yes

Threat only at high elevations?  no

Risk assessment results:  More information needed; score: 9 (Go to the risk assessment)

Common name(s): [more details]

English: couch panicum, creeping panic, quack grass, torpedo grass, Victoria grass, wainaku grass

French: millet rampant, panic rampant

Manobo: kayana

Spanish: canota, grama del norte

Tagalog: luya-luyahan

Habit:  grass

Description:  "An erect, rather wiry, creeping, perennial grass, 30-90 cm tall, growing extensively but not densely, rhizomes strongly developed, often swollen or knotty, smooth with brownish or whitish scales, branched, sending out erect culms from the rather distant nodes; culms clothed at base with bladeless sheaths; leaf sheaths fringed with long hairs along the margin, ligule short, fringed with hairs; blades two-ranked, 15 to 25 cm long, 1.5 cm wide or less, acuminate, linear, flat or folded, with a rounded base, smooth or somewhat rough, sparsely long-hairy above, smooth below, covered with a whitish bloom, somewhat rigid, with long white hairs behind ligule, midrib prominent and keeled; panicles exserted, 7 to 18 cm long, somewhat loose and open, erect or ascending, sometimes nodding, elongated, scattered, one to three at each node, branches stiffly ascending, distant, 2 to 19 cm long, smooth or slightly rough; spikelets two-flowered, pale green or pale yellow, often tinged with purple, oblong-ovate, acute or slightly acuminate, 2.2 to 3 mm long; first glume truncate, about one-fifth as long as the spikelet, second glume as long as spikelet, seven- to nine-nerved; first lemma as long as spikelet, five- to nine-nerved; first palea nearly as long as spikelet; anthers yellowish orange; second lemma shorter than spikelet; stigmas purple; caryopsis lanceolate, straw-colored.  The sharp-pointed rhizome which is coarse, swollen, and shaped like a ginger rhizome and the blades which are often covered with whitish waxy bloom are the distinguishing characteristics of this species" (Holm et al., 1977; p. 353).

Description from World Grass Species.

Habitat/ecology:  "Primary a weed of moist, coastal, sandy soils, it can also grow on heavy upland soils and can tolerate drought.  It is found most frequently in sandy soils along seacoasts or in poorly drained heavy soils.  It cannot stand permanently flooded conditions, but can withstand occasional flooding and can encroach upon and invade ditches, drains, watercourses, fishponds, and floating mats of vegetation from banks and adjacent areas.  It is frequent in cultivated lands, grasslands, roadsides, and gardens.  It is usually found in low coastal areas and along rivers but it does spread to local inland areas to elevations of 1,500 to 2,000 m in the tropics.  It grows best in open sunny areas but can stand partial shade.  It is very drought-resistant, an the rhizomes may live through prolonged dry periods" (Holm et al., 1977; pp. 353, 356).  Grows up to elevations of 2,000 m in Indonesia.  Favors open sunny conditions, but can stand partial shade.  Rhizomes can stand prolong dry periods  (Waterhouse, 1994; pp. 172-177).  In Hawai‘i, "naturalized in usually moist, disturbed habitats, such as along ditches and roadsides in cane fields, 30-1,100 m"  (Wagner et al., 1999; pp. 1571, 1573); "infests coastal sites and mesic to high-rainfall environments; forms thick, dense stands that smother low plants"  (Motooka et al., 2003).

Propagation:  "The plant spreads mainly by course, extensively creeping rhizomes that may extend as far as 7 m from the parent plant. Seeds are produced in a few situations" (Holm et al., 1977; p. 353).

Native range:  Tropical and north Africa, Mediterranean; now widespread in the tropics.

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	Saipan Island	native	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 52)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Saipan Island		Bishop Museum (Honolulu) (1984) (voucher ID: BISH 573466) Taxon name on voucher: Panicum repens L.
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 1571, 1573)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 1571, 1573)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Starr, Forest/Martz, Kim/Loope, Lloyd L. (2002) (p. 23) East Maui. Voucher cited: Starr & Martz 980927-1 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 1571, 1573)
Palau Palau (main island group)	Koror Island	native	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 52)
Palau Palau (main island group)	Koror Island	introduced invasive	Space, James C./Waterhouse, Barbara/Miles, Joel E./Tiobech, Joseph/Rengulbai, Kashgar (2003) (p. 81)
Palau Palau (main island group)	Palau Islands (main island group)		Bishop Museum (Honolulu) (1977) (voucher ID: BISH 428554) Taxon name on voucher: Panicum repens L.
Philippines Philippine Islands	Philippine Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)

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		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (p. 355)
Cambodia Cambodia	Cambodia (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Indonesia Indonesia	Indonesia (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Japan Japan	Japan (country)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Mexico Mexico	Mexico (United Mexican States)		Hafliger, Ernst/Scholz, Hildemar (1980) (p. 86)
Negara Brunei Darussalam Brunei	Brunei (Negara Brunei Darussalam)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)
Singapore Singapore	Singapore (Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)
Taiwan Taiwan	Taiwan Island	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Thailand Thailand	Thailand (Kingdom of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Vietnam Vietnam	Vietnam (Socialist Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Indian Ocean offshore islands) Cocos (Keeling) Islands	Cocos (Keeling) Islands	native	Orchard, Anthony E., ed. (1993) (p. 38)
Seychelles Seychelles Islands	Seychelles Islands	introduced	Weber, Ewald (2003) (p. 298)

Control: 

Physical: "Difficult because of extensive rhizomes beneath soil surface. Tillage only encourages its growth"  (Motooka et al., 2003).

Chemical:  "Sensitive to glyphosate and imazapyr but will require repeat treatments" (Motooka et al., 2003).

Additional information:  Information from the book "Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide" (Motooka et al., 2003). (PDF format).
Photos and additional information at University of Florida, Center for Aquatic and Invasive Plants (see thumbnails above).

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

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

References:

Bishop Museum (Honolulu). 1977. Voucher specimen #BISH 428554 (Otobed, D.O. PW-10007).

Bishop Museum (Honolulu). 1984. Voucher specimen #BISH 573466 (Raulerson, L. 6861).

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

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

Haselwood, E. L./Motter, G. G. 1983. Handbook of Hawaiian Weeds. Second edition, revised and expanded by Robert T. Hirano. University of Hawaii Press. 491 pp.

Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. 1977. The world’s worst weeds: distribution and biology. East-West Center/University Press of Hawaii. 609 pp.

Motooka, Philip/Castro, Luisa/Nelson, Duane/ Nagai, Guy/Ching, Lincoln. 2003. Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. 184 pp.

Motooka, Philip/Ching, Lincoln/Nagai, Guy. 2002. Herbicidal Weed Control Methods for Pasture and Natural Areas of Hawaii. Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai‘i. CTAHR free publication WC-8.

Orchard, Anthony E., ed. 1993. Flora of Australia. Vol. 50, Oceanic islands 2. Australian Government Publishing Service, Canberra.

Space, James C./Waterhouse, Barbara/Miles, Joel E./Tiobech, Joseph/Rengulbai, Kashgar. 2003. Report to the Republic of Palau on invasive plant species of environmental concern. USDA Forest Service, Honolulu. 174 pp.

Starr, Forest/Martz, Kim/Loope, Lloyd L. 2002. New plant records from the Hawaiian archipelago. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2000. Part 2: Notes. Bishop Museum Occasional Papers. 69:16-27.

U. S. Government. 2006. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2007. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Waterhouse, D. F. 1993. The major invertebrate pests and weeds of agriculture in Southeast Asia. The Australian Centre for International Agricultural Research, Canberra. 141 pp.

Waterhouse, D. F. 1994. Biological control of weeds: Southeast Asian prospects. Australian Centre for International Agricultural Research, Canberra. 302 pp.

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