Reader Marie recently asked:
Q: What can I use to control poa in my bermuda sod?
A: While many people might first think of Power of Attorney when they see a reference to poa, Marie is asking about a species of turfgrass called Poa annua. You might know it better as annual bluegrass. While poa is technically a turfgrass, its aggressiveness in taking over the less grassy portions of some lawns leads many to treat it as an invasive weed. And since each plant can produce multiple generations of seed each season, controlling unwanted poa can make securing power of attorney look like a walk in the park.
Adding to Marie’s trouble is the fact that her poa, a cool-season grass, is growing in a warm-season lawn. That means the poa is just getting started in the fall when her bermudagrass is bedding down for the season. That makes the poa especially visible in the cooler months when the soil temperature dips below 70 degrees Fahrenheit.
But as it happens, that seasonal difference is also the best place to start dealing with unwanted poa. The best time to exert control over the grass is in early fall and early spring, when the poa is starting to grow. A pre-emergent herbicide applied at either of these times will inhibit the growth of cool-season weeds, preventing them from producing the seeds that would otherwise establish next year’s crop.
That said, half the battle is simply helping your chosen turfgrass to thrive. While poa annua is quick to spread to just about any unoccupied patch of lawn space, it isn’t particularly competitive with existing plants. If you can coax your Bermuda grass into spreading and establishing itself continuously across your lawn, it should squeeze out the existing poa during the heat of summer, leaving it with fewer footholds during the following autumn.
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Photo by Macleary Grass Man through Creative Commons licence