Introduction:
Canada bluegrass (Poa pratensis)
A rhizomatous grass that is regarded as a crop in some systems, but as a weed in others. It is highly valued as a pasture and turf grass, particularly in golf courses. However, it is considered an invasive weed in natural grassland ecosystems where it outcompetes native species and reduces biodiversity and alters nitrogen cycling and ecosystem function.
Description:
Poa pratensis is a perennial, cool season mat-forming grass. The wide, creeping rootstock produces underground runners and leafy shoots. Runners creep under the surface of the ground and produce upright leafy stems from their ends. The stems are from 15cm to 1m in height, and eventually develop into flower-bearing stems. Seedhead panicles have an open-pyramid shape and produce numerous small seeds. Each branch of the panicle carries several spikelets which are bluish green to purple. Each spikelet has four to five flowers enclosed within two glumes of equal size. Leaves are smooth, soft and measure 1/8 to ¼ inch wide and 6 to 12 inches long with keeled tips. Canada bluegrass (Poa pratensis) can be distinguished from other grasses by its narrow leaf blade which is V-shaped in cross section and boat-shaped tip.
Occurs in:
Agricultural areas, range/grasslands, ruderal/disturbed, scrub/shrublands.
Habitat description:
Canada bluegrass (Poa pratensis) can grow in many habitat types including meadows, roadsides, forest edges, dry hills, marshes and along seashores.
General impacts:
Canada bluegrass (Poa pratensis) Distribution in North America shown in green.
Sod forming grasses such as Poa pratensis are known to have negative effects on native prairie species in the northern Great Plains of the United States. It outcompetes native plant species and reduces biodiversity in invaded areas. For example the vital rates and population growth rate of a native grass, Anemone patens was greatly reduced when growing among P. pratensis and other invasive grasses.
Litter produced by Canada bluegrass (Poa pratensis) forms thick mats of “slicks” on the soil surface. Litter from Kentucky bluegrass is known to inhibit seedling establishment of other plant species.
Canada bluegrass (Poa pratensis) has been found to disrupt ecosystem function by altering nitrogen cycling and carbon storage, lowering plant diversity and shifting seasonal forage production. These impacts affect livestock production, wildlife habitat and ecosystem services.
Uses:
Canada bluegrass (Poa pratensis) has value as a pasture grass and hay. It is palatable and is of high fattening value, and provides excellent forage for early livestock grazing. It is also used for beautification of parks and home lawns, and as a turf that is useful for heavy use areas such as campgrounds, golf fairways, picnic areas and ball fields. It is also used in erosion control due to its dense, vigorous turf forming habit. This plant also provides food for elk, deer, rabbits and turkey. Its seeds are eaten by birds and rodent.
Despite being a non-native grass species, Poa pratensis provides important habitat and oviposition sites for the rare grass skipper Polites mardon in the United States.
Geographical range:
Native Range: Europe, northern Africa, Siberia and North America, Australia, southern parts of South America.
Introduced Range: Antarctica, Canada, Falkland Islands, French Southern Territories, Mexico, New Zealand, Saint Helena, South Africa, South Georgia and South Sandwich Islands, United States.
Management information:
Controlled areas should be closely monitored because seeds of Kentucky bluegrass can remain viable for two years and the plant can continue to
Canada bluegrass (Poa pratensis) Close up.
spread by tillers and rhizomes.
Physical: Mowing and raking are generally ineffective against Canada bluegrass (Poa pratensis), and can actually stimulate rhizome and tiller production. Therefore mowing is not recommended.
Burning: Burning of Canada bluegrass (Poa pratensis) can have variable results. Some studies have found Canada bluegrass (Poa pratensis) to be negatively affected by fire. Timing of the prescribed burn, moisture and site conditions are important factors that may influence the response of the plant to burning. It is also important to consider native species composition of the area and what species will replace Canada bluegrass (Poa pratensis). Burning usually needs to be repeated annually for several years.
Chemical: Glycophosphate is effective in reducing infestations of Poa pratensis. Imazapyr and sulfometuron methyl can also provide control. However chemical control may not be the preferred method of control in some regions due to the effect on native species.
In field experiments performed in the UK, found Poa pratensis to be moderately resistant to resistant to all graminicide herbicides tested. It was only moderately susceptible to susceptible to the broad-acting Glycophosphate in spring and autumn. Resistance was greater with autumn-applied herbicides than with spring applications. Established plants were more resistant than young plants.
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