Poa annua is a winter annual that germinates in the late summer/early fall once soil temperatures fall below 70 degrees. Seedlings mature in the fall, are in a vegetative state in the winter, and flower and produce seed in late spring and early summer. You may be able to control poa annua with Green-Up with Crabgrass Preventer if applied in the early fall. This will keep the poa annua seeds from sprouting. But keep in mind that poa annua seeds are tough and can survive many seasons without germinating. This method will work towards reducing poa annua in the lawn over time. You will need to treat your lawn for many seasons in order to rid it completely of this weed. There are some herbicides that will selectively kill poa annua in lawns, but they can only be applied by certified professionals. Round-Up will also kill poa annua, but it will also kill any other plants that it comes in contact with. Avenger, non-selective organic spray will also kill poa annua, but it will also kill any other plants that it comes in contact with.
Tips for preventing poa annua:
- Avoid overwatering
- Poa annua prefers shady and damp areas. If you water deeply and infrequently, its shallow roots won’t be able to reach down to where the moisture is.
- Set your mower high (3 – 4 inches)
- Poa annua is short. When you mow your grass high, between 3-4 inches, you make it hard for annual bluegrass to survive.