What is the deal with Poa?

poa annua in warm season grass
Image sourced from Bayer Turf & Ornamentals Management

It’s not uncommon to get a few calls each spring from homeowners wondering what type of weed is growing in their otherwise healthy lawn.  During the early spring, there is a good chance that weed is poa annua, commonly known as annual bluegrass.   

Poa annua, or Annual Bluegrass, is a common winter annual weed found in local lawns during the spring each year.  It mainly germinates in the fall with the season’s first cool rains and stays pretty tiny until the following spring.  Its lighter green color and prolific seed heads make it easy to spot, especially in dormant warm-season lawns like Bermudagrass or Zoysiagrass. Still, poa annua can be found in Fescue, too.  

How do you control poa annua?

The best defense against this pesky weed is the application of a pre-emergent weed control product.  Applying pre-emergent herbicide in the early fall, before poa annua germinates, will form a barrier in the soil to prevent any seedlings from breaking through.  This is an excellent option for warm-season Zoysiagrass or Bermudagrass lawns.  Fescue lawns, however, are not a good candidate for a fall pre-emergent application.  The good news for Fescue lawns is as long you overseed your lawn annually and maintain a thick, healthy turf, poa annua tends to be less apparent than it is in the brown, dormant warm-season grasses. 

There are several different pre-emergent products labeled for poa annua control, and we utilize the best based on the latest university trials and recommendations.  However, as with any product used on your lawn, mother nature has the final say on effectiveness and longevity of control.  Since poa annua favors wet soils and cooler conditions, we tend to see more breakthroughs in rainier conditions 

Post-emergent herbicides are another option to control poa annua that has already germinated, especially in warm-season grasses.  These liquid products will help kill existing annual bluegrass clumps, but they will not prevent new clumps from popping up.  The efficacy of these weed control products is also temperature-dependent.  The warmer the temperature, the more active the plant is.  The more active the plant is, the more herbicide it uptakes. It’s kind of like me, I tend to work a little slower when I’m cold, but when the sun is shining, I am a busy bee! 

In cool-season turf, such as Fescue, our post-emergent options are very limited and as a general rule not nearly as effective.  Removing an unwanted cool-season grass, like poa annua, from a desirable cool-season grass, like Fescue, is very hard to do without damaging both grasses.  For Fescue lawns, it is best to let Mother Nature do the work.  Once temperatures reach the 80’s or above consistently, poa annua will naturally die out on its own.  It is a cool-season grass, after all, so warm temps are not the best growing conditions for this troublesome weed.   

It’s also worth noting that once temperatures reach the 80’s or above consistently, poa annua will naturally die out on its own.  It is a cool-season grass, after all, so warm temps are not the best growing conditions for this troublesome weed.   

What’s the good news about this grassy weed?

The good news is you are our customer, and we will continue to do everything in our power to prevent and control annual bluegrass.  With the help of our consistent fertilization and weed-control programs and your proper mowing and watering, together, we can keep this weed in check.   

Are you concerned about poa annua in your lawn? Don’t hesitate to reach out to your Route Ambassador or our friendly customer service team.  We are here to Help Happy Grow! 

Posted Under: News & Tips