eXtension

New weed taking over my yard

Asked May 20, 2020, 10:32 AM EDT

I recently noticed a new weed coming into my grass. This new weed looks like grass except it is lighter green and forms seeds much sooner than normal grass. It is spreading into my yard from the neighbors yard to the west (see photo with lighter green on left side). There are also small patches in other parts of the yard (see photo). Also a close up photo. My questions are: What is this new weed, and is there some way to get rid of it. We just built this house 4 years ago, and spent a lot of time and money on having the grass put in, and it is now very thick and beautiful. We have an irrigation system, and pay a commercial company to fertilize and treat for weeds five times per year. Thanks in advance for the help. Matt (810) 348-6026

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Ingham County Michigan

1 Response

The grass found infesting your Kentucky bluegrass lawn was identified as annual bluegrass (Poa annua).

Annual bluegrass is a clump-forming winter annual grass that is a major problem in residential and commercial lawns. It reproduces by seed and the clumps enlarge by aggressive tillering. Annual bluegrass appears light green in color when compared with other grasses and thus, makes it visually incompatible. It grows best in cool, moist, and rich soils but tolerates a variety of conditions.

Trying to control annual bluegrass is extremely challenging for homeowners as well as commercial lawn care specialists. Homeowners are usually advised to either manage what is there or kill the areas with glyphosate (Roundup, others) and replant or re-sod. There are several cultural practices that will reduce the presence of annual bluegrass. Excess irrigation will encourage the growth of annual bluegrass. Therefore, reducing the irrigation frequency should allow the established Kentucky bluegrass to out-compete the annual bluegrass. Avoiding excessive fertilization should also reduce the presence of annual bluegrass. Annual bluegrass produces the most seedheads during the month of May. Therefore, bagging grass clippings during this time will prevent further spread.