How and When to Remove Unwanted Grass from Your Lawn

Replanted patch of grass in a lawn

Patch of grass that's been sprayed with herbicides and replanted from seed

How and when do I get rid of unwanted grass species and patches of weeds in my yard?

Fall is a great time to fix up your lawn and to tackle those patches of unwanted grass species and weeds. Even the most well-tended lawns can be infiltrated by uninvited seeds, but in the fall, your work will have the greatest chance of success. Herbicides are most effective this time of year, and it’s a great time to plant many new types of grass.

The process is as simple as killing or removing the unwanted grass, smoothing the dirt, then replanting with the desirable grass – but what’s most important is your timing. Follow these tips to time your lawn spruce up correctly:

  • Allow Six-Weeks for Herbicide Sprays: If you’re using a spray herbicide such as Roundup or an organic vinegar-based spray, allow six weeks between spraying and replanting to give the spray time to work and to dissipate so it won’t kill the new grass seed. To plan ahead, simply decide when you want to plant your new seed, and count backward six weeks on the calendar to plan your spray date. Before replanting, rake away as much of the dead grass as you can, and smooth any lumps in the soil.
  • Lawn with grass killed by herbicide spray

    Grass killed by herbicide spray

  • Hand Digging Grass Removal: If you’re digging up the unwanted grass without chemicals, you can replant the same day. Just dig up the unwanted sod, replace with rich topsoil, and replant with new grass. You can do this project any time grass can be planted in your area.
  • Fall Grass Planting: If you’re planting cool-season grasses in fall, you’ll need to spray in late summer in order to plant by October. If you’re like me and tend to forget until it’s too late in the season, just spray the unwanted grass anytime in the fall, and wait until spring to replant.
  • Spring Grass Planting: Warm-season grasses should be planted in the spring anyway. If you’re planning to re-seed with a warm-season grass next spring, you can spray an herbicide on unwanted grasses any time before the first fall frost. If you’re trying to green up your lawn with winter rye, you’ll need to spray six weeks before planting.


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9 Comments on “How and When to Remove Unwanted Grass from Your Lawn”

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  • Dee Says:
    October 4th, 2018 at 9:46 pm

    Think twice before using Roundup.

  • Official Comment:

    Thomas Boni Says:
    August 24th, 2018 at 10:59 am

    Hi, Marie! Apply a fungicide when the low temperature at night is 60 degrees Fahrenheit. You should use a product that is specifically formulated to treat brown patch. You’ll need to apply it according to the product label’s frequency, which is usually every two to four weeks.

    Of course, good lawn care and maintenance also apply. Remember to not over-water and not over-fertilize.
    Good luck!

  • Marie Page Says:
    August 23rd, 2018 at 5:52 pm

    I asked WHEN to treat a fungus in a fescue lawn and did not see an answer? Thank you.

  • Official Comment:

    Thomas Boni Says:
    June 27th, 2018 at 2:11 pm

    Hi, Harold,

    Gardening questions can be tricky since the rules can change based on the region. We would suggest contacting your local Master Gardeners association.
    Master gardeners train on a range of topics so they can provide advice, at no charge, for people in their area.

    Thanks for your question, and good luck!

  • Harold Brace Says:
    June 13th, 2018 at 1:19 pm

    Shell I spread a fungus tretment before I dig up old soil

  • Deborah Manselle Says:
    July 23rd, 2015 at 7:36 am

    I am new to MO and have a problem with a kind of spike like grass in my otherwise nice lawn. It grows so fast it is always sticking up above the rest of the lawn within a day of mowing. I hate the look and want to get rid of it, but am not sure what it is called so I can look it up. Please help.

  • Mr James E. McMillan Says:
    April 7th, 2014 at 2:43 pm

    I have this grass in my backyard, which turns brown in the fall thru the spring, then turns green during the late spring until the end of early fall. It’s great looking when it’s green; looks better than the other grass, really thick. But I want to remove it (don’t like the brown look most of the year). Should I use roundup to rid this grass in the fall and replant for next summer?

  • Official Comment:

    Ben Erickson Says:
    May 4th, 2012 at 9:27 am

    Hi Ron,
    Your question has been answered on our website by Julie Day in her article on When to Plant After Using Roundup (glyphosate) Weed Killer.

  • Ron Says:
    March 2nd, 2012 at 1:50 pm

    As I understand Roundup can be used and can plant 2-3 days later?

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How and When to Remove Unwanted Grass from Your Lawn