lawn weed identification

Asked May 18, 2014, 10:16 AM EDT

Can someone identify a pesky grassy weed in our lawn? Yellow clumps, shown in attached pics. If I'm entitled to 2 questions - how to eliminate/control it? Thanks very much. Dennis PS - I took pics at several magnifications, but am only "allowed" to upload 1!

Sussex County Delaware

1 Response

Hello, Dennis,

Thank you for contacting Delaware Cooperative Extension. Without seeing a sample of the weedy grass you have and looking at the blade tips under the microscope, I cannot tell for sure. You are welcome to send a sample in through your local county Extension office (Carvel Center in Georgetown for Sussex). However, I think it looks like annual bluegrass, Poa annua. Annual bluegrass is favored by the cool wet conditions we have had recently. The bright green color should not be as noticeable as the other grass types like fescue fill in on your lawn. Try to keep evenly mowed so that the annual bluegrass does not go to seed.
Excessive water promotes annual bluegrass. Nitrogen fertilizer applied in the spring may also promote annual bluegrass. You should be applying lawn fertilizer only in the fall. There are pre-emergent herbicides that can be applied in the late fall to early winter that will kill the seed of the annual bluegrass so they do not produce plants next spring. Those chemicals need to be applied by a professional applicator.

My best,