Annual Bluegrass (poa annua) is a winter annual grassy weed found from Florida to New England and west to California. It is considered a weed in Charlotte’s Fescue and Bermuda lawns, but is actually planted on some lawns and golf courses in other parts of the country.. In our area PoaA germinates in early November, matures over the winter, sets seed and dies in the spring. Right now the weed is very noticeable with it’s white seed heads and bunch type growth. This weed grows everywhere in shade and sun. You’ll see it on roadsides, open fields, golf courses and residential lawns. Once we hit the 80 degree mark on a consistent basis, the PoaA plants will begin to turn brown and die.
The PoaA has gone absolutely crazy this spring. Weather conditions have been perfect for this weed invasion. We just went through the wettest fall and winter on record. This Spring has also seen above average precipitation. The Winter was relatively mild and recent cool nights have kept the PoaA growing and seeding rapidly. There is no viable way to spray out PoaA in Fescue lawns. Several Ag Companies have new products claiming control in Fescue. We have field tested all of the newer products and saw less than acceptable results. These products are very expensive and have to be applied 3 times within 30 days at costs exceeding $200 per acre. We can not justify asking our customers to spend several hundred dollars on a treatment program for PoaA with no guarantee for control.
The vast majority of the PoaA seed comes from the soil itself. Seeds can lay dormant in the soil for years and are brought to the surface through aeration and heavy rainfall. Birds, insects, wind and rain run-off can spread seeds from lawn to lawn. Unless you use blue tag certified, 0% weed content grass seed in the fall you run the risk of spreading the problem.
Right now the best thing you can do to mitigate the issue in Fescue lawns is to mow it at the highest setting (3 3/4-4 inches.). Cutting the grass short will increase PoaA seed production and force the plant to thicken. There are a couple of viable options to alleviate the PoaA problem next spring. Early aeration/seeding (Aug-Sep) and late fall pre-emergent is one option. Foregoing aeration and just seeding the lawn is another option that worked for me.