Poa Annua or Annual Bluegrass is a pesky lawn weed which invades both warm and cool season lawns. In the winter, annual bluegrass forms bright green patches that goes dormant for warm-season lawns. In cool-season lawns, annual bluegrass blends well in the spring, but when warm weather comes around the weed will die leaving thin or bare areas which other weeds often invade.
Annual Bluegrass Characteristics
Annual Bluegrass prefers dark, shady areas to grow properly. With extreme heat and sunlight, the lawn weed will leave brown patches around your lawn. Typically, annual bluegrass has shallow roots; light color patches, and produces seeds. Since this lawn weed has short roots, you should mow your grass at approximately 3 to 4 inches. Tall grass will prevent less annual bluegrass problems.
Annual Bluegrass Growth & Prevention
Early fall, Annual Bluegrass poa seeds will start to germinate and begin its growth process. For preventative measures, you will need to use a pre-emergent in late August or early September. Pre-emergent products that can control crabgrass will also be effective on Annual Bluegrass. Some suggested products are prodiamine and dithiopyr. These products will help prevent the growth of Annual Bluegrass and the seeds from germinating in the fall.
If Annual Bluegrass or Poa Annua becomes a dominant lawn problem, please contact your local lawn care professional for further details and instructions to reseed your lawn, or other effective lawn programs available.