The Biology of Canadian Weeds: 160. Poa pratensis L.

Kentucky bluegrass ( Poa pratensis L.) is a perennial, cool-season grass that is widespread across all provinces and territories and first mentioned as an invasive species in 1879. It is represented in Canada by six subspecies, three of which are native, two introduced, and one native and introduced. As a group, the subspecies are found across a wide range of habitat types, including prairie grasslands, woodlands, tundra, and disturbed sites. The introduced subspecies have been intensively used in forage and turf breeding and production. The most invasive subspecies, Poa pratensis ssp. angustifolia, is native to temperate Eurasia and was introduced to North America as a forage and cover crop. Invasions by Kentucky bluegrass result in fewer and less abundant native grass and forb species, reducing plant diversity in native prairie grasslands, and creating cascading negative effects on the ecosystem goods and services provided by these systems. Rhizomatous growth and its ability to reproduce asexually through aposporous apomixis likely enhance Kentucky bluegrass invasiveness. It is effectively controlled using glyphosate herbicide. Early-season prescribed burns are also emerging as a potential management strategy. Despite its detrimental impacts on grassland diversity, Kentucky bluegrass remains a valuable turf and forage grass in all Canadian provinces and territories.