The Green Plague Called Annual Bluegrass

A slew of green freckles isn’t welcome on dormant Southern lawns.

Annual Bluegrass patches in lawn
Photo: Steve Bender

Folks up north love green winter lawns, but down South we settle for brown. We actually like the tawny colors of Zoysia, Bermuda, St. Augustine, and Centipede that remind us of carpets. Unfortunately, green spots and patches of winter weeds often mar our desired monochromatic perfection. One of the worst offenders is annual bluegrass (Poa annua).

A cousin to the perennial Kentucky bluegrass (Poa pratensis) commonly used where summers are mild, annual bluegrass germinates in fall, grows in winter, sets seeds in spring, and then dies. When it croaks, you raise your eyes to the heavens and give thanks to the Big Guy -- but hold your horses. Thousands of seeds lurk in the lawn all summer, waiting to sprout and drive you crazy once more.

Such a calamity befell Judy and me after we finished laying new Zoysia sod last summer. It was immaculate – not a weed in sight. Come winter, though, green tufts emerged from cracks between pieces of sod. If we waited for them to die, they'd shower the Zoysia with seeds and give us a repeat performance. We girded our loins and decided. The annual bluegrass must go!

Annual Bluegrass
Steve Bender

What you see above is a nylon weed bag filled with approximately 15 pounds of annual bluegrass plants Judy and I dug out from an area of about 600 square-feet using my vicious hand weeder that works like the claws of Wolverine. Many plants had already sent up flower stalks, so time was of the essence. I emptied in the bag in the woods, lest any seeds contaminate my compost bin. Then we filled it again.

A Good Solution

Here's a solution for the less crazed. We admit it. When it comes to things like weeds, we are not normal people. Once we pull one weed, we must pull them all. You, however, might prefer a resolution that takes less time and is easier on the back and knees. Do these two things.

First, thicken up your lawn to leave fewer bare places for seeds to sprout. Fertilize Southern grasses in mid-spring and mid-summer. Don't mow any lower than 1½ inches, because the lower you mow, the more weeds you get.

Second, apply a crabgrass preventer, such as Scott's Halts according to label directions in September. It keeps grassy weeds from sprouting, including annual bluegrass. Once you've significantly reduced the annual bluegrass population, you can stop with the crabgrass preventer and just pull up the occasional clump.

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