Poa compressa
(Canada bluegrass)

Pictures

Picture	Title	Caption	Copyright
Title Flowering habit Caption Poa compressa (Canada bluegrass); flowering habit. Commanster, High Ardennes, Belgium. June 2006. Copyright ©James K. Lindsey-Ecology of Commanster/via wikipedia - CC BY-SA 2.5	Flowering habit	Poa compressa (Canada bluegrass); flowering habit. Commanster, High Ardennes, Belgium. June 2006.	©James K. Lindsey-Ecology of Commanster/via wikipedia - CC BY-SA 2.5
Title Habit Caption Poa compressa (Canada bluegrass); habit. The rhizomatous habit is evinced by the separate stems arising from ground level (no basal leaf bunch in this species). The narrow panicle is also characteristic. Nr Bozeman, Montana, USA. July 2007. Copyright ©Prof Matt Lavin-2009/Bozeman, Montana, USA - CC BY-SA 2.0	Habit	Poa compressa (Canada bluegrass); habit. The rhizomatous habit is evinced by the separate stems arising from ground level (no basal leaf bunch in this species). The narrow panicle is also characteristic. Nr Bozeman, Montana, USA. July 2007.	©Prof Matt Lavin-2009/Bozeman, Montana, USA - CC BY-SA 2.0

Identity

Preferred Scientific Name

• Poa compressa L.

Preferred Common Name

• Canada bluegrass

Other Scientific Names

• Paneion compressum (L.) Lunell
• Poa compressa f. depauperata Millsp.
• Poa compressa var. sylvestris Torr.
• Poa langeana Rchb.
• Poa pallens Poir.
• Poa planicularis F.H.Wiggers
• Poa planiculmis Weber
• Poa polynoda Parn.
• Poa subcompressa Parn.
• Poa thurmanniana Montandon

International Common Names

• English: Canadian bluegrass; flattened meadow grass
• Spanish: poa comprimada
• French: pâturin comprimé; pâturin du Canada
• Chinese: jia na da zao shu he
• Portuguese: poa-chata

Local Common Names

• : English bluegrass; wire grass
• Canada: creeping Poa; smaller blue grass; Virginia blue grass
• Germany: Rispengras, Flaches; Rispengras, Platthalm-; Rispengras, Zusammengedrücktes
• Italy: gramigna compressa; ruba lana; strappa lana
• Japan: koichigotsunagi
• Korea, Republic of: jompoapul
• Netherlands: beemdgras, plat
• Russian Federation: mjatlik spljusnutyj
• Sweden: groee, berg-
• USA: flat-stem bluegrass

EPPO code

• POACO (Poa compressa)

Summary of Invasiveness

P. compressa (Canada Bluegrass) is a rhizomatous perennial grass species native to Europe and parts of Asia, which was introduced into the USA in the early 1800’s as the grass grew very well on poor soils. It is now widely spread throughout North America from Newfoundland to Alaska and all the continental United States except Florida and is present in all states of New England. It is also present in New Zealand where it is fully naturalised. Some consider it an invasive weed: it is present on a number of invasive plant lists in North America, and is banned in Connecticut (St John et al., 2012) and listed as invasive and “potentially of national concern” in Canada (Native Plant Database, 2015). It can reproduce by both seeds and rhizomes, can be spread long distances by cattle and deer carrying seeds, and establishes well in disturbed areas (St John et al., 2012). However, it is still sometimes planted in pastures, and used for erosion control on disturbed sites. P. compressa does not appear to outcompete other grasses unless on poor soil, but once established is difficult to eradicate due to proximity to native species.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Poa
•                                 Species: Poa compressa

Notes on Taxonomy and Nomenclature

Poa compressa is a member of the family Poaceae. It was one of the many species described in Species Plantarum by Carl Linnaeus in 1753. Poa is Greek for fodder and compressa is Latin for flattened, named for the flattened stems which are only present in this one species in the genus Poa. One of the common names for this species is Canada (or Canadian) bluegrass, reflecting its early introduction to Canada. 

Description

The following description comes from the Flora of China Editorial Committee (2015): Perennials, strongly rhizomatous, shoots extravaginal. Culms wiry, compressed, erect, often geniculate at base, simple or sparsely tufted, 15–50(–60) cm tall, 1.5–2 mm wide, nodes compressed, 3–6, 2–5 exserted. Leaf sheaths compressed to keeled, smooth, uppermost closed for 1/10–1/5 of length; blades flat, 5–12 cm × 1.4–4 mm, surfaces smooth or adaxially scabrid; ligule 1–3 mm, abaxially scabrid, truncate to obtuse. Panicle contracted or slightly open, erect, narrow, 4–11 × 0.5–1(–3) cm; branches erect or steeply ascending, or eventually spreading, 1–3 per node, densely scabrid angled from base, longest 2–4 cm with spikelets moderately crowded from the base or in distal 2/3. Spikelets ovate-lanceolate, 3.5–5 mm, florets 2–4; glumes lanceolate, nearly equal, 2–3 mm, 3-veined, apex acute or thinly mucronate, keel scabrid, rachilla smooth or minutely bumpy; lemmas oblong, 2.3–3.5 mm, apex obtuse, keel shortly villous for 2/3 of length, marginal veins to 1/3, intermediate veins faint, areas between veins glabrous; callus sparsely webbed or glabrous; palea keels scabrid. Anthers 1.3–1.8 mm. Caryopses 1.5 mm long.

Plant Type

Distribution

P. compressa is native to Europe and southwestern Asia (Clark and Malte, 1913), but has now spread worldwide as an introduced species. It is widely spread throughout North America from Newfoundland to Alaska and all the continental United States except Florida (USDA-NRCS, 2015). It is also present and naturalized in eastern Australia and New Zealand (USDA-ARS, 2015). It is infrequent in China, and perhaps present only as an introduction here (Flora of China Editorial Committee, 2015). USDA-ARS (2015) includes North Africa (Algeria and Morocco) in the native range.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

P. compressa was introduced into Canada in the late 1700’s (St John et al., 2012) and into much of North America in the early 1800s (Clark and Malte, 1913). It was found along the Saskatchewan River in Canada in 1823 and at other isolated locations unfrequented by European explorers by the early 1800s (Oakley, 1910). It has since spread throughout almost all the continental USA and Canada. The spread in North America is thought to have been as a contaminant of Kentucky bluegrass (P. pratensis) seed (St John et al., 2012). It has been cultivated for pastures in poor soils (Hitchcock, 1951). It was introduced into New Zealand and is now fully naturalized (Edgar, 1986).

Introductions

Risk of Introduction

The species is already very widely spread, but may be introduced to new sites for erosion control and low maintenance landscaping. Once introduced, it has the potential to spread into adjoining plant communities under ideal climatic and environmental conditions (St John et al., 2012). It is expected to appear in Heilongjiang because it is common on the Russian side of the border with China (Flora of China Editorial Committee, 2015).

Habitat

P. compressa is unable to compete with other grasses on good soils and generally develops best on soils of low fertility or poor drainage. It has moderate drought and salinity tolerances but is not shade tolerant (US Forest Service, 2016). In the UK, Hubbard (1959) records it as occurring in poor, thin grassland, on dry banks, on waste ground, mostly on shallow, well-drained soils; also on old walls and ruins.

Habitat List

Biology and Ecology

Genetics

Chromosome number is 2n=42 (St John et al., 2012).

Reproductive Biology.

P. compressa is apomictic (St John et al., 2012). Seeds germinate between 20 and 30°C and prechilling temperatures of 10^°C increase germination rates. The US Forest Service (2016) indicates that it also needs light for germination. The species is reported as flowering in May to June in Canada (Native Plants Database, 2015) and June to August in China (Flora of China Editorial Committee, 2015). P. compressa also spreads by rhizomes (St John et al., 2012).

Physiology

P. compressa has C₃ physiology.

Environmental Requirements

Canada Bluegrass is adapted to wet sites but thrives on moderately acidic and droughty soils with poor fertility, including rocky outcrops and mountain tops (St John et al., 2012; Invasive Plant Atlas of New England, 2015). In Canada, it grows best on clay or clay loam soil (Oakley, 1910; Clark and Malter, 1913). It is not very competitive on fertile soils. Seeds require direct light for germination (Invasive Plant Atlas of New England, 2015).

Climate

Air Temperature

Rainfall

Soil Tolerances

Soil drainage

• free
• impeded

Soil reaction

• acid
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• infertile

Means of Movement and Dispersal

P. compressa has been deliberately introduced by man into new countries for use as a forage grass on poor soils, for controlling erosion on disturbed sites, and for low maintenance landscaping. It has also been spread by contamination of P. pratensis seed. Once introduced, it is spread effectively locally by rhizomes, and over longer distances through the numerous tiny seeds, dispersed by both wind and animals (Invasive Plant Atlas of New England, 2015). Cattle and deer can carry P. compressa seeds long distances (Klein, 2008).

Pathway Causes

Impact Summary

Environmental Impact

P. compressa may become weedy or spread from its intended growing area (for erosion control or landscaping) to adjoining plant communities and displace more desirable vegetation if not properly managed (St John et al., 2012). In Alaska, it is reported to have little impact on native plant communities or successional processes (Klein et al., 2008). In New England, it does not pose a large threat to undisturbed natural areas, but has potential to be a nuisance in areas recovering from disturbance, and could crowd out native species when it grows in dense clumps (Invasive Plant Atlas of New England, 2015). Together with P. pratensis, it can out-compete native species for light and water in British Columbia (Garry Oak Ecosystems Recovery Team, 2015).

In trying to reestablish the Lakeside Daisy (Hymenoxys acaulis var. glabra) at the upland habitats of Lockport and Romeoville Prairies, Illinois, proliferation of herbaceous plants, including P. compressa, has shaded and/or outcompeted the daisy, making control of P. compressa and other introduced plants vital to this endangered species (US Fish and Wildlife Service, 1990).

Threatened Species

Risk and Impact Factors

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Is a habitat generalist
• Pioneering in disturbed areas
• Tolerant of shade
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Competition - monopolizing resources
• Competition - shading

• Highly likely to be transported internationally accidentally
• Difficult to identify/detect as a commodity contaminant

Uses

Clark and Malte (1913) reported that on poor clay soils, P. compressa grew better than the related pasture grass P. pratensis (Kentucky Blue Grass). Its’ early use was as a permanent pasture grass which thrived under close grazing. More recently, St John et al. (2012) state that the primary use is for controlling erosion on disturbed sites such as roadsides and mined land, heavily used recreational areas, and for low maintenance landscaping. The grass provides food for deer, small mammals and birds, which utilize both the seeds and leaves (St John et al., 2015; Illinois Wild Flowers, 2015; Native Plant Database, 2015).

Uses List

Animal feed, fodder, forage

• Fodder/animal feed

Environmental

• Erosion control or dune stabilization

General

• Ornamental

Similarities to Other Species/Conditions

P. compressa is very similar in appearance to P. pratensis (Kentucky Bluegrass) but is distinguishable by its flattened stems, which are found in no other cultivated species of the genus Poa (Clark and Malte, 1913). The leaves on P. compressa are not as broad and numerous as those on P. pratensis. Flowers in P. pratensis are in a panicle which is more pyramidal in shape, the lower branches being numerous at each joint. In P. compressa, the panicle is generally oblong, or narrowly egg-shaped (Clark and Malter, 1913).

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

In Canada, where P. compressa is an invasive plant of potential national concern, the recommended control method is cutting (Native Plant Database, 2015). While as a weed in agricultural settings it can be controlled by herbicides including tebuthiuron (Stroud et al., 1977), chemical control is not typically recommended in natural settings as the grass generally occurs in mixed stands together with native species (Garry Oak Ecosystems Recovery Team, 2015). Burning of young plants in late spring can be effective, but should only be undertaken with expert advice as the effects vary with timing and species composition (Garry Oak Ecosystems Recovery Team, 2015). Klein (2008) suggests a combination of mechanical and chemical methods, but warns that eradication efforts are likely to also damage coexisting species as P. compressa is often in close proximity to other plants.

References

Atlas of Living Australia, 2015. Atlas of Living Australia. http://bie.ala.org.au/

Clark GH; Malte MO, 1913. Fodder and Pasture Plants. Ottawa, Canada: Dominion of Canada Department of Agriculture, 143 pp.

Czarapata EJ, 2005. Invasive plants of the upper Midwest: an illustrated guide to their identification and control [ed. by Czarapata, E. J.]. Madison, USA: University of Wisconsin Press, xx + 215 pp.

EDDMapS, 2013. Early Detection & Distribution Mapping System. USA: The University of Georgia - Center for Invasive Species and Ecosystem Health. http://www.eddmaps.org/

Edgar E, 1986. Poa L. in New Zealand. New Zealand Journal of Botany, 24(3):425-503.

Flora of China Editorial Committee, 2015. Flora of China. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=2

Garry Oak Ecosystems Recovery Team, 2015. Poa compressa and pratensis. Canada and Kentucky bluegrass. http://www.goert.ca/documents/P.compressa+pratensis.pdf

Gray A, 1908. Grey's New Manual of Botany: A Handbook of the Flowering Plants and Ferns of the Central and Northeastern United States and Adjacent Canada, Seventh edition [ed. by Robinson BL, Fernald ML]. Chicago, USA: American Book Company, 926 pp.

Hitchcock AS, 1951. Manual of Grasses of the United States. USDA Miscellaneous Publication No. 200. Washington DC, USA: USDA.

Hoffman R; Kearns K, 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin manual of control recommendations for ecologically invasive plants, Publ. ER-090 97. Madison, WI, USA: Bur. Endangered Resources, Dept. Natural Resources, 103 pp.

Hubbard CE, 1959. Grasses. London, UK: Penguin Books.

Hulten E, 1968. Flora of Alaska and neighboring territories, a manual of the vascular plants. Stanford, USA: Stanford University Press.

Hulten E, 1968. Flora of Alaska and neighboring territories. Stanford, California, USA: Stanford University Press.

Illinois Wildflowers, 2015. Canada bluegrass, Poa compressa. http://www.illinoiswildflowers.info/grasses/plants/cn_bluegrass.htm

Invasive Plant Atlas of New England, 2015. Canada bluegrass datasheet. https://www.eddmaps.org/ipane/ipanespecies/grass/Poa_compressa.htm

Invasiveorg, 2015. Canada bluegrass, Poa compressa L. http://www.invasive.org/browse/subinfo.cfm?sub=6214

Jung MingJer; Soreng RJ; Kuoh ChangSheng, 2006. Notes on grasses (Poaceae) for the flora of Taiwan (II). Taiwania, 51(3):240-248. http://tai2.ntu.edu.tw/taiwania

Kentucky Exotic Pest Plant Council, 2015. Kentucky Exotic Pest Plant Council Species List. http://www.se-eppc.org/ky/list.htm

Klein H, 2008. Canada Bluegrass (Poa compressa)., USA: Alaska Natural Heritage Program, University of Alaska. http://accs.uaa.alaska.edu/invasive-species/non-native-plant-species-list/

Native Plant Database, 2015. Poa compressa, Canada bluegrass. https://nativeplants.evergreen.ca/search/view-plant.php?ID=04546

New Zealand Plants, 2015. Nga Tipo o Aotearoa - New Zealand Plants. Manaaki Whenua - Landcare Research databases. http://nzflora.landcareresearch.co.nz/

Oakley R, 1910. Canada bluegrass: its culture and uses. Farmers Bulletin, 402:19 pp.

Pacific Northwest Invasive Plant Council, 2015. Pacific Northwest Noxious Weed List. http://depts.washington.edu/waipc/pnwnoxiousweedlist.shtml

Rose F; Stokoe WJ; Jackson AB, 1974. The observer's book of grasses, sedges and rushes (Observer's pocket series No. 7). London, UK: Frederick Warne and Co. Ltd.

Royal Botanic Garden Edinburgh, 2015. Flora Europaea. Edinburgh, UK: Royal Botanic Garden Edinburgh. http://rbg-web2.rbge.org.uk/FE/fe.html

Royal Botanic Gardens Kew, 2015. The Herbarium Catalogue. Richmond, Surrey, UK: Royal Botanic Gardens Kew. www.kew.org/herbcat

St John L; Tilley D; Winslow S, 2012. Plant guide for Canada bluegrass (Poa compressa). USDA-Natural Resources Conservation Service.

Stroud DJ; Johnson GB; Perkins AT, 1977. The effects of application timing on the control of Canadian bluegrass (Poa compressa) using tebuthiuron, a soil residual herbicide. In: Proceedings North Central Weed Control Conference, 1977, Vol. 32. 127.

Swearingen JM, 2009. Survey of Invasive Plants Impacting National Parks in the United States. Washington, DC, USA: National Park Service. http://www.invasiveplantatlas.org/parksurvey.pdf

US Fish and Wildlife Service, 1990. Recovery plan for the Lakeside Daisy (Hymenoxys acaulis var. glabra). Twin Cities, Minnesota, USA: US Fish and Wildlife Service, 80 pp.

US Forest Service, 2016. Poa compressa. http://www.fs.fed.us/database/feis/plants/graminoid/poacom/all.html

USDA-ARS, 2015. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

USDA-NRCS, 2015. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/

Virginia Department of Conservation and Recreation, 2015. Virginia Invasive Plant Species List 2014. http://www.dcr.virginia.gov/natural-heritage/document/nh-invasive-plant-list-2014.pdf

Distribution References

Anon, 1997. Wisconsin manual of control recommendations for ecologically invasive plants. In: Wisconsin manual of control recommendations for ecologically invasive plants, [ed. by Hoffman R, Kearns K]. Madison, Wisconsin, USA: Bur. Endangered Resources, Dept. Natural Resources. 103 pp.

Atlas of Living Australia, 2015. Atlas of Living Australia., http://bie.ala.org.au/

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI

CABI, Undated b. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Edgar E, 1986. Poa L. in New Zealand. New Zealand Journal of Botany. 24 (3), 425-503.

Flora of China Editorial Committee, 2015. Flora of China., St. Louis, Missouri; Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=2

Garry Oak Ecosystems Recovery Team, 2015. Poa compressa and pratensis. Canada and Kentucky bluegrass., http://www.goert.ca/documents/P.compressa+pratensis.pdf

Hitchcock A S, 1951. Manual of Grasses of the United States. In: USDA Miscellaneous Publication. Washington DC, USA: USDA.

Illinois Wildflowers, 2015. (Canada bluegrass, Poa compressa)., http://www.illinoiswildflowers.info/grasses/plants/cn_bluegrass.htm

Invasive Plant Atlas of New England, 2015. Canada bluegrass datasheet., https://www.eddmaps.org/ipane/ipanespecies/grass/Poa_compressa.htm

Invasiveorg, 2015. Canada bluegrass, Poa compressa L., http://www.invasive.org/browse/subinfo.cfm?sub=6214

Jung MingJer, Soreng R J, Kuoh ChangSheng, 2006. Notes on grasses (Poaceae) for the flora of Taiwan (II). Taiwania. 51 (3), 240-248. http://tai2.ntu.edu.tw/taiwania

Klein H, 2008. Canada Bluegrass (Poa compressa)., USA: Alaska Natural Heritage Program, University of Alaska. http://accs.uaa.alaska.edu/invasive-species/non-native-plant-species-list/

Native Plant Database, 2015. Poa compressa, Canada bluegrass., https://nativeplants.evergreen.ca/search/view-plant.php?ID=04546

New Zealand Plants, 2015. Nga Tipo o Aotearoa - New Zealand Plants. Manaaki Whenua - Landcare Research databases., http://nzflora.landcareresearch.co.nz/

Royal Botanic Garden, 2015. Flora Europaea., Edinburgh, UK: Royal Botanic Garden Edinburgh. http://rbg-web2.rbge.org.uk/FE/fe.html

Royal Botanic Gardens Kew, 2015. The Herbarium Catalogue., Richmond, Surrey, UK: Royal Botanic Gardens Kew. http://www.kew.org/herbcat

Swearingen JM, 2009. Survey of Invasive Plants Impacting National Parks in the United States., Washington, DC, USA: National Park Service. http://www.invasiveplantatlas.org/parksurvey.pdf

USDA-ARS, 2015. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysimple.aspx

USDA-NRCS, 2015. The PLANTS Database. Greensboro, North Carolina, USA: National Plant Data Team. https://plants.sc.egov.usda.gov

Links to Websites

Contributors

15/12/2015 Original text by:

Belinda Luke, CABI, UK

Distribution Maps