Annual Bluegrass can be identified as a bunch-forming type of grass that grows in dense patches. Its ligule is medium to long and slightly pointed, and its collar is narrow and smooth. This grassy weed has sheaths that are slightly compressed and smooth with short blades that have parallel edges terminating in a boat-shaped tip. The seeds germinate in late summer, early autumn and spring.
This plant is often sold as a species of turf grass—and sometimes isn't considered a lawn weed. Due to the fact that it's able to adapt to different climates and growing conditions, Poa annua can be found in a wide range of habitats throughout much of North America. These grassy weeds are annuals, meaning they live for only one season and are typically easy to control because they lack the complex underground structures needed to spread new plant growth through creeping roots. Still, annuals produce tons of seeds that can infest and dominate your yard under the right conditions.
Annual Bluegrass is a lawn weed that is difficult to control culturally. It has the ability to adapt to numerous lawn-mowing heights, which is a large reason why it is frequently used on golf course greens and fairways. For weed removal, professionally applied, pre-emergent herbicides are the best way to control Annual Bluegrass.