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Grassy weed ID #929278
Asked April 22, 2026, 4:52 PM EDT
Lincoln County South Dakota
Expert Response
Dear Marcus,
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YOUR QUESTION #0199193:
Grassy weed ID
I am having trouble figuring out and trying to control this grassy weed in my yard. Looks like crabgrass but it is perennial. South side of Sioux Falls. Seems to grow with rhizomes.Ask Extension offers one-to-one expert answers from Cooperative Extension/University staff and volunteers within participating Land-Grant institutions across the United States.
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Unfortunately, with Quackgrass and other prairie grasses that invade our lawns, there isn't a specific product that will eliminate one and leave the preferred grass. Any grass specific herbicide will eliminate both.
And don't feel bad, I have had to battle this grass for years before deciding a non-grass landscape was the only solution.
If you just have a few spots, control as I said will be any grass specific herbicide (I cant give you a recommendation on products however). The best time is the fall, around the time of the first frost. This is when grasses are bringing carbohydrates into the roots for winter, and thus the herbicide is most likely to kill those rhizomes in your picture.
Regarding round up. Originally glyphosate was the main chemical that would kill weeds, however there are now several brands of roundup that contain different chemicals, so be aware that you don't purchase something that could harm your trees or other broadleaf perennials.
Now, hopefully if this has killed the Quackgrass, it will have most likely also killed your lawn, so then the next spring you will have to re-seed/replant your lawn. Unfortunately that is quite a bit of work for a homeowner. And if this is in your neighbors lawn, or you miss any of the rhizomes, don't be surprised if it starts to spread back in.
https://extension.umn.edu/weeds/quackgrass
If you only have a few just getting established, pulling out the rhizome, or using a paintbrush to lightly coat Quackgrass leaves can be effective without the damage to the rest of the lawn.
I wish you success with what is a very difficult problem to solve. Remember, a thick, tall lawn is also one of the most effective tools at preventing a takeover of weeds. Fertilize 2x a year (about now and then in August) with a mostly nitrogen fertilizer, mow infrequently especially during the hot summer months and always at the highest mower setting. I usually wait to mow until just before it rains to ensure the lawn has an easier recovery and mow maybe once or twice from late june through early august unless its been a particularly wet year again so the grass can avoid drought stress.
