Q: At first I thought I had nutgrass but now I’m not so sure. Can you ID what I have?
A: I’m not sure which is harder to control…nutgrass or the Virginia buttonweed you actually have. Buttonweed is TOUGH to bring under control. It spreads from seed readiliy, roots from branch nodes and can even root from pieces your mower throws out when you mow.
Although it is classified as a broadleaf plant, it does not respond to broadleaf herbicides as readily as one would like.
I think the best product to use (assuming you have fescue or zoysiagrass ) is triclopyr (Ortho Weed B Gon for Chickweed and Oxalis). But if you have bermudagrass or centipedegrass you have to use regular Weed B Gon or Trimec Southern.
You’ll need at least three applications at six week intervals (or whatever the label directs) to start seeing control.
One other option to consider is applying imazaquin (Image for Nutgrass) alternately with the broadleaf herbicides listed above.
Glyphosate (Roundup, Killzall, etc) will kill buttonweed but will kill nearby turfgrass too.
You have a tough row to hoe…better to get started sooner rather than later!