Annual bluegrass, scientifically named Poa annua, is an annual plant belonging to Poaceae, or grass, family. The word poa is Greek for fodder, although this particular grass is not regarded as a particularly useful livestock fodder. Also known under the names annual meadow grass, common meadowgrass, and walkgrass, it grows up to a maximum height of about 1 foot (0.3 m). This low-growing grass is found throughout most of the world, especially in places with temperate climates. The flowers of annual bluegrass bloom in yellow or pale green throughout the year, except during severe winters.
Having both male and female organs, the flowers can self-pollinate, though the grass also benefits from wind pollination. This grass has light to dark green foliage, and the short leaves have a smooth texture, are blunt at the tips and tend to droop. Annual bluegrass produces brown seeds that typically ripen during the months of April to November.
This plant is considered easy to grow as it can survive in fine to coarse soils that are well-drained but moist. Annual bluegrass can also grow in very acidic and nutritionally poor soils. It prefers sunny locations, as it does not do well in the shade. The plant can withstand cool temperatures down to 47 degree Fahrenheit (about 8.3 degrees Celsius). It attracts the caterpillars of many butterfly species, of which it acts as a food source.
The natural habitats of the annual bluegrass include wastelands, cultivated land, and grasslands. This grass is also found on lawns where it acts as a lawn cover or lawn grass. Patches of this grass may turn brown during the summer, as it has a tendency to die out in very hot weather. It is propagated by seed, and aside from being found on lawns, it is also utilized on golf putting greens.
In most cases, cultivation is not required as the seeds readily drop from the plant, resulting in a rapid seed spread rate. Some regions of the United States, such as Nebraska, Illinois, and Wyoming, have included this grass on their list of invasive weeds. In these areas of the world, the concern involves controlling its spread rather than encouraging it. Other than the rapid rate of seed spread, the seeds also lay dormant for years before sprouting, making the grass difficult to control and eradicate. Control is still possible with the use of pre-emergent herbicides, which prevent the seeds from germinating.