What is Poa Annua or Annual Bluegrass?

Poa Annua, or annual bluegrass, is one of the most common grassy weeds in the United States. It looks very similar to Kentucky bluegrass, except it is a lighter shade of green, has a shallower root system, and develops a short seed head early in the season. It usually dies off in the summer when the weather gets hot, leaving behind bare spots in your lawn. Poa annua germinates in late summer or early fall. The seedlings grow throughout the fall and then flower the following spring. To keep it out of your lawn, spread a grassy weed preventer, like Scotts® WeedEx™ Prevent with Halts®, in late summer before seeds sprout.

How to Prevent Poa Annua

Avoid Overwatering

Poa annua is widely adapted to growing in different conditions, though it prefers the damp, shady areas of your lawn. Fight the weed by watering your lawn deeply and infrequently. Its shallow roots won't be able to reach down to where the moisture is.

For more information see our Lawn Watering Tips.

Set Your Mower High

Poa annua is short. When you mow your grass high, between 3 to 4 inches, you make it hard for annual bluegrass to survive. Lawns with taller grass tend to have very few Poa annua problems.

Check out these lawn mowing tips.

Fertilize Regularly

If your lawn is thick and lush, weeds like Poa annua will have a hard time becoming established. A well-maintained lawn doesn't leave any room for weed seeds to sprout. To keep your lawn thick and Poa annua at bay, feed your grass regularly (4 times per year) with Scotts® Turf Builder® lawn fertilizer products. Remember, each feeding should be spaced 6 to 8 weeks apart.

For more information on fertilizer timing, read When to Feed for a Greener Lawn.

Use a Pre-Emergent in Late Summer

The Poa annua seeds produced in the spring wait patiently in the soil for the cooler temperature of fall to arrive before they sprout. You can stop them from sprouting by applying a pre-emergent weed control product, like Scotts® WeedEx™ Prevent with Halts®, in early fall (August through early September). Follow up your pre-emergent weed control application with an application of Scotts® Turf Builder® WinterGuard® Fall Lawn Food to help your lawn recover from the stresses of summer and keep it thick and green.