Poa pratensis L., Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  yes

Risk assessment results: 

High risk, score: 14 (Go to the risk assessment (Pacific)).
High risk:  (Go to the risk assessment (United States)) (PDF format).

Other Latin names:  Poa angustifolia L.

Common name(s): [more details]

Chinese: cao di zao shu he

English: Kentucky bluegrass, smooth meadow grass, smooth-stalked meadowgrass

French: pâturin des prés

Spanish: grama de prados, poa común, poa de los prados, zacate poa

Habit:  grass

Description:  "Perennials with extensive rhizomes forming a dense sod; culms slightly compressed, erect, (2-) 3-6.5 (-10) dm tall.  Sheaths smooth, but occasionally somewhat scabrous, closed to ca. 1/2 their length; ligule 0.5-1.7 (-3) mm long, margins usually entire, apex truncate; blades numerous, soft, usually green but occasionally glaucescent, flat or usually folded, 1-3 (-4.5) mm wide, margins usually scabrous, sometimes slightly pubescent and purple-tinged near collar, apex strongly boat-shaped.  Panicles open, often pyramidal, (2-) 4-5 (-9) per node; spikelets green or purple-tinged, 2-4-flowered, crowded, ovate, (3-) 4-5 (-6) mm long, strongly compressed; glumes scabrous on keel, first glume 1.8-2.5 (-3) mm long, 1-nerved, second glume 2.2-3.3 mm long, 3-nerved; lemmas 2.5-4 mm long, 3-5-nerved, lateral nerves weak, base with copious cobwebby hairs, keel and marginal nerves sericeous, glabrous between the nerves, apex obtuse or acute; palea nearly as log as lemma.  Caryopsis reddish brown, ellipsoid, ca. 1.5 mm long"  (Wagner et al., 1999; p. 1584).

Description from GrassBase.

Habitat/ecology:  "Grassland, riparian habitats, freshwater wetlands.  Where native, this grass is commonly found in meadows, pastures and disturbed sites.  It is invasive because it spreads rapidly and forms dense swards that crowd out native vegetation.  Populations reach high shoot densities and the large size makes it highly competitive to native grasses and forbs"  (Weber, 2003; p. 336).

In Hawai‘i, "naturalized in disturbed mesic to subalpine forest and alpine sites, 1,220-4,025 m"  (Wagner et al., 1999; p. 1584).

Propagation:  Seed

Native range:  "Europe, widely naturalized in temperate and montane tropical regions" (Wagner et al., 1999; p. 1584).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Pacific offshore islands) Lord Howe Island	Lord Howe Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 23) "Introduced...as a pasture grass". Vouchers cited: A.C. Beauglehole 5421 (CANB, MEL), A.C. Beauglehole 5422 (CANB, MEL)
Australia (Pacific offshore islands) Norfolk Islands	Norfolk Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 12) "Introduced...as a pasture grass". Voucher cited: F.C. Allen 179 (CHR)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 556)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced	Skottsberg, Carl (1953) (p. 215) In several places on the south side, large tufts on the shore.
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 556)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1584) Voucher cited: Forbes 263.H (BISH)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1584)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1584)

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)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Canada Province of British Columbia	Canada (British Columbia)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Chile (continental) Chile	Chile (Republic of)		Hafliger, Ernst/Scholz, Hildemar (1980) (p. 121)
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 285)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 192) var. pratensis, var. angustifolia Smith and var. hirsuta Asch. & Graebn.
New Zealand New Zealand	New Zealand (country)	introduced invasive	Edgar, E./Connor, H. (2000) (p. 176) "Lowland to alpine in grassland and pasture, cultivated or waste ground".
United States (west coast) United States (west coast states)	USA (Oregon)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
United States (west coast) United States (west coast states)	USA (Washington)	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
Mascarene Islands Mascarene Islands (Mauritius, La Reunion, Rodrigues)	Mascarene Islands	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Control:  Control information from the Bugwood Wiki.

Physical:  Dig out single plants, making sure to remove all pieces and rhizomes.

Chemical:  Treat with herbicide (Weber, 2003; p. 336).

Additional information:
Information from the Fire Effects Information System.
Information from the Bugwood Wiki.

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

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

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

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido. 2006. Nouveau catalogue de la flore vaculaire de l'archipel Juan Fernández (Chile) [Nuevo catálogo de la flora vacular del Archipélago Juan Fernández (Chile)]. Acta Bot. Gallica 153(4):399-587.

Edgar, E./Connor, H. 2000. Flora of New Zealand, vol. V: Gramineae. Manaaki Whenua Press. .

Hafliger, Ernst/Scholz, Hildemar. 1980. Grass weeds, vol. 2. CIBA-GEIGY Ltd., Basle, Switzerland. 137 pp. + plates.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

Orchard, Anthony E., ed. 1994. Flora of Australia. Vol. 49, Oceanic islands 1. Australian Government Publishing Service, Canberra.

Skottsberg, Carl. 1953. The natural history of Juan Fernandez and Easter Island. Vol. II, Botany. Almqvist &l; Wiksells, Uppsala. 960 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. 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).

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

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