Is this grassy weed Poa trivialis (aka Roughstalk bluegrass)?

Asked March 31, 2020, 4:21 PM EDT

Is the lime colored grassy weed shown in the attached photos Poa trivialis (Roughstalk bluegrass) as shown on your web page at https://extension.umd.edu/hgic/topics/weed-identification-photos? If yes, do you have any further advice to control this beyond what's shown on above web site? If no, what is it. This grassy lime colored weed first appeared in my tall turf-type fescue lawn about three years ago. Fig-1 shows a typical circular patch of this weed in my lawn. I've seen similar patches in several neighborhood lawns. The weed in my yard seems to out compete my fescue and recurs each year. I 've had very limited success digging it out. The weed is fast growing. Fig-2 shows the height difference two days after cutting the lawn. Any help getting rid of this weed would be gratefully appreciated. Sincerely, Patrick Martin

Montgomery County Maryland

1 Response

Hi Patrick,
Yes, this is Poa trivialis. It is most noticeable now, in early spring. You mention two id characteristics, its light green color, and fast, aggressive growth habit. You will have to continue combatting as you have been for a couple of reasons. First, there is no selective herbicide to control it.
Secondly, Montgomery County’s pesticide law bans the use of most synthetic pesticides, including herbicides, insecticides, and fungicides on private lawns, playgrounds, mulched recreation areas, and childcare facilities. Organic pesticides are allowed (they will not control Poa trivialis at all!). Go to the following website for information regarding the law and organic lawn care information, www.MontgomeryCountyMD.gov/lawns

You can also ask them questions, Email AskDep@MontgomeryCountyMD.gov or call 240-777-0311.

Deb