Grass going to seed already? Might be Poa Annua and NOT Kentucky Bluegrass

Poa annua, also known as annual bluegrass, is a low-growing grassy weed that is commonly found in lawns throughout the Chicagoland suburbs.

We're starting to see some lawns with grass sporting seedheads in the Chicago suburbs that look a lot like Kentucky Bluegrass (KBG), but wait! It's most likely an aggressive weed - Poa Annua and NOT Kentucky Bluegrass...ouch...

Poa annua, or annual bluegrass, is a low-growing grassy weed commonly found in lawns throughout the United States. Because it so closely resembles desirable grass types such as Kentucky Bluegrass, it often goes unidentified until the infestation becomes large.

It very closely resembles Kentucky bluegrass. However, there are some key differences that should help you identify it. One of those key differences is color. Poa annua will usually have a lighter green color that shows up in clumps within the rest of your lawn. The leaves are smooth, and have a boat shape tip at the end.

The easiest way to identify Poa annua is by looking at the flowered seed heads that form. Your other grass types might flower at this point, too, but this is where you can see the difference in the flower heads and be able to identify Poa annua.

Poa annua has a very thin set of flowers that form outward and are not dense. Kentucky Bluegrass has a very dense cluster of flowers that point upward.

There are two ways to prevent Poa Annua in your lawn:

1 - Prevent it: Apply a pre-emergent in late summer. Most people only spread one application of pre-emergent in early spring but we should be spreading THREE distinct apps throughout the year to handle all weeds. Two half applications in spring and one full app, of another pre-emergent type in late summer. We can use Dithiopyr 0-0-7, or Prodiamine 0-0-7.

2 - Selective or non-selective herbicide: Most selective herbicides do not work well for established Poa Annua plants, so non-selective (kills everything) herbicides are the go-to.

Regardless of how we remove the Poa Annua, we will need to reseed the area or allow the existing Kentucky Bluegrass to spread into the newly bare spot, which can take some time.