Red bladed crabgrass?

Asked August 10, 2019, 4:02 PM EDT

I have an invasive lawn plant with a growth habit like crabgrass, but the upper portion of the blades is purplish-red. I have used "Spectracide Weed Stop for Lawns plus Crabgrass Killer", but with no results to date, and of course it is going to seed now!! It really looks just like crabgrass!! What would you suggest I do to get rid of it? It has formed large patches.

Jackson County Oregon

1 Response

It's extremely difficult to identify your weeds without actually seeing one. There is a "Large Crabgrass" species with a a lot of pink/purple in the stems, but not necessarily at the tips of the leaves. There are many perennial weeds such as quackgrass and bermudagrass with growth habits like crabgrass, but not necessarily with a purple top. There is also an annual weed (dies away in winter; propagates by seed) known as a sandbur which tends to have purplish black stems. You are correct in assuming that a spray for crabgrass does not necessarily kill other types of weeds. Also, many weed killers do not work when the temperature is above 80 degrees.
Unfortunately, not eliminating the weed when it was first apparent may mean you will have to take drastic action: dig out the patches or use a weed killer on each patch of the invasive. Make certain you dig out all the rootlets, etc. then in September, reseed those patches. Grass seed will germinate rapidly in cooler weather and you will have a nice lawn again in the spring. We strongly recommend you take a sample of the weed to the OSU Master Gardener Plant Clinic, open weekdays from 10 to 2 and located at 569 Hanley Rd.(Rte. 238), Central Point in the Extension Building toward the back of the complex. They can help you choose the correct herbicide if that is the route you want to take or give you further information on renovating the lawn. There are also some publications that will give you information: EB0607 from Washington State Extension and EM 8776,
( Perennial Weed Management) available from Oregon State Extension at extension.oregonstate.edu/publications Several pamphlets on general lawn care are also available for downloading or reading on site.