Identifying noxious week in lawn

Asked September 12, 2016, 10:43 AM EDT

Hi, I have a fast-spreading weed in my lawn that is taking over. I've never seen it before and don't know how to treat it. Can you identify it and recommend how to deal with it? I've enclosed photos. It's starting to bloom now and getting ready to seed. It looks similar to crabgrass with clumps of tall, thick narrow stems, but has sprouted soft purple blooms on top in recent days. It's really invasive. Thanks.

Montgomery County Maryland

1 Response

This looks like a seedling from the ornamental grass,Pennisetum alopecuroides. Varieties such as 'Moudry' often have purple coloration. It’s not unusual for the ornamental varieties to make viable seed which can germinate in landscape beds or in turf areas. We would not recommend they be transplanted to a new spot as an ornamental, because they will continue to infest your lawn.

In your lawn, spot treatment with glyphosate is effective. Large numbers of seedlings can be difficult to manage in turf as there aren’t many selective herbicide options after emergence. A preemergence product would work if they were an ongoing problem. There is some concern that they could become invasive like some of the Miscanthus cultivars. For information on the parent plant see -