The grass is dormant, the lawnmower is in the shed, and the sprinkler system is off for the year. You walk outside to enjoy the late winter afternoon only to notice that your lawn is filled with clumps of green grass. What you are seeing is Poa Annua or Annual Bluegrass. It is an annual grassy weed that germinates in the fall and begins to grow in the late winter and early spring. In Athens, you might see it in the late fall and early winter as well if the weather stays mild. It grows in a clump and will rapidly mature, forming thousands of seeds. These seeds will stay dormant in your lawn until next fall when the cycle begins again.
Photo Credit: MSU College of Ag
Not only does Poa Annua create unsightly clumps in your dormant lawn making you have to mow when you shouldn’t have to, but it also creates thin spots in your lawn. As the Poa Annua grows, it overpowers the dormant turf grasses. The clumps continue to grow until it gets hot outside in June, then Poa Annua dies out leaving you with a bare spot until the turf fills back in. In the meantime, other weeds are going to try and establish themselves in the bare spots. This is why it is recommended to stop Poa Annua from ever beginning to grow in your yard.
Photo Credit: Weed Genomics
How do I prevent it?
A quality pre-emergent is your safest and most cost-effective way to prevent Poa Annua in your lawn. Apply the pre-emergent by September 15th for best results. Your pre-emergent will need to be watered in to become effective. You will have up to 14 days after application to water it, but the sooner, the better.
But wait, you put down pre-emergent and still have Poa Annua?
Unfortunately, Poa Annua has become resistant to the most common pre-emergent that is sold in big box stores and what most lawn care companies use in their fall applications. Since it is so cheap, it is used often, however, we recommend a pre-emergent called Specticle. It can be purchased in both liquid and granular forms. We recommend homeowners use the granular option since it is easier to control. It can also be used in your landscape beds to keep the weeds from taking over your mulch and pine straw. Our preferred rate is 3 lbs per 1000 square feet of Bermuda and Zoysia in September and another 3 pounds per 1000 square feet 60-90 days later. For Centipede and St. Augustine, you will only need 1.5 to 2 lbs per 1000 square feet at the same time as Bermuda and Zoysia.
What can I do to get rid of it?
This depends on the time of year that you are trying to attack it. If it is early in the season (October-March), you can treat it with a few herbicides. After March, it is best to let the Poa Annua die out naturally from the heat. The products that will kill Poa Annua are usually specialized and not easily found in a store (Certainty and Revolver). Most lawn care companies, in order to kill the Poa Annua, will blanket spray the entire lawn with RoundUp while the grass is dormant. WE DO NOT RECOMMEND ANY HOMEOWNER TO DO THIS. This extra use of chemicals is not necessary if a good pre-emergent is used in the fall. If you do have some Poa Annua pop up, you can spot spray it with a non-selective herbicide or a selective herbicide. Please read the label carefully and apply it as directed. If buying chemicals, mixing, spraying, and safely storing them is not your cup of tea then hire a reputable lawn care company in Athens that can help prevent the Poa Annua before it ever becomes a problem in your lawn.