Poa annua grass can be controlled with a pre-emergent herbicide applied in the early fall and early spring. However, care must be taken when applying this herbicide as it can kill other types of plants as well as the poa annua grass. Poa annua grass cannot grow in a dense, thick lawn, so keeping a thick lawn is another method of controlling this annoying weed.
Left to grow, poa annua grass can quickly take over a lawn. The plant produces several hundred seeds each season and the seeds may lie dormant for many years before sprouting. Poa annua grass, often referred to as annual bluegrass, is identifiable by its tall seed stalk. In hot weather, poa dies, leaving ugly yellow spots in the lawn. Because it germinates in the early spring and fall, it is important to treat the yard during these times.
Treating the poa annua grass with a pre-emergent herbicide may help to control this weed, when applied at the right time. This herbicide will prevent the poa from germinating, effectively keeping the seeds from sprouting. Because the poa seeds are strong and lie dormant for many years, multiple applications of an herbicide may be necessary.
Another option may be to allow the lawn to grow longer than usual. This makes the poa annua easier to see, allowing the homeowner to pull it out by with roots.