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How to Kill Crabgrass “Look-a-Likes”

March 29, 2012

Whenever I hear someone say they have crabgrass in their lawn now before spring has really kicked in, I suspect they are really referring to one of the perennial grassy weeds that looks different than their good grass.  Crabgrass plants do not show up until summer after they germinate in spring.  Perennial grassy weeds live year after year, so you can see them in your lawn year round.

Some of the most common perennial grassy weeds are:  Coarse Fescue, Quackgrass, Nimblewill, Timothy Grass, and Orchard Grass to name a few.  Nimblewill is a little bit tricky so it very frequently gets confused with crabgrass.  The reason is even though Nimblewill is a perennial, it goes dormant in winter taking on a brown color until around May.  So folks think it is dead crabgrass.  Be sure to look at both the early spring picture of dormant Nimblewill and the summer pictures showing actively growing Nimblewill.

I have some good news for you.  Roundup has a Gel product that makes it a lot easier to kill the grasses you want to kill without killing the grasses you want to keep, especially if they are growing taller than your good grass.  Click here to read all Roundup Gel.  As with all Roundup products, you still need to be careful not to spray your good grass.  And more good news, you can seed those spots in 7 days after treating.

Dormant Nimblewill in Early Spring is often confused with dead crabgrass. Roundup will kill it once it begins growing in Late Spring.

Nimblewill that is not dormant during Summer is often confused with Crabgrass

Quackgrass is often confused with Crabgrass

Coarse Fescue is often confused with Crabgrass

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  1. The link above takes us to the “Sure Shot” page, which advises as follows:

    “Where Not to Use
    Do not spray plants or grasses that you like – they will die. Not recommended for spot weed control in lawns since glyphosate kills lawn grasses.”

    That seems completely inconsistent with “good news” as to how to kill look-alikes — especially when you couple it with pictures of the look-alikes in lawns.

    • Hi Bill:
      Thanks for your comment. I should have made it very clear that the Roundup Sure Shot Foam will still kill the good grass around the weed you are trying to kill if the spray gets on that good grass. To me the good news is that of all the Roundup sprays, the Sure Shot Foam is the easiest to control where it goes. You still need to use it with care. The package copy you cited is on all Roundup labels so folks understand it will kill your good lawn grass if you spray it. Good Luck with your lawn.

  2. Mary permalink

    I have an aggressive weed that has taken over my entire lawn. It has a purplish- flower. I have tried many weed products. Nothing seems to work! We invested in a lawn service for over 4 years and all they can tell me is that my neighbors lack of interest in taking care of their lawn is the culprit! I decided that I am wasting my money for them to come and mow “weeds” . Please help. Do I need to dig up the grass, or is there something that can help the lawn return to it’s former state?

    • Hi Mary
      There are several weeds with purple flowers that come to mind. Henbit is a winter annual that has purple flowers now, spreads lots of seed in the lawn during spring, then dies in summer. The whole process is repeated when it germinates in Fall, only there are more plants each year. Ortho Weed-B-Gon MAX plus Crabgrass Control works well on this weed anytime. Killing it now will help some, however spraying in the fall before it has a chance to flower and produce seed is the main way you will get rid of it. The good news is this particular Ortho Weed-B-Gon product takes care of over 200 kinds of weeds without harming your good grass, so there is a pretty goood chance it will get your problem weed. Once exception with purple flowers that I can thing of is Wild Violets. This weed is a perennial and mainly grows in partly shaded areas. Ortho Weed-B-Gon Chickweed and Clover Killer works well on this weed. Other weed controls do not do as good a job. Hope this helps!

  3. Jill permalink

    I also have Wild Violets. We have applied our first application of Ortho Weed B Gone checkweek and Clover Killer. I know it’s going to take a few applications. How long do I wait inbetween treatments? Also, can I also treat my lawn with Turf builder Plus 2 on the off weeks?
    We also need to do some patch lawn seeding to keep other weeds out. How long do I have to wait to apply that?

    • Hi Jill
      You can spray WeedBGon chickweed and clover killer a second time in 2 to 3 weeks if you are not seeing complete kill of your Wild Violets. You can seed 1 week after your last spray of this product. If you were to use Turf Builder with Plus 2 in the same area, you would need to wait at least a month before seeding.

  4. Eleanor permalink

    I have identified, by looking at photos on a university agriculture site and your photos, the following weeds present in our lawn. Nice collection, huh?
    wild garlic
    carpetweed possibly
    annual bluegrass
    dormant Nimblewill
    coarse fescue

    What do I do? I am slightly overwhelmed at this point and do not have the money to get rid of it and start over or pay someone to do it. It is an L shaped lawn with pool in middle so really not a tremendous amount of grassy area. 60 x 130 ft but that’s the L shape with a 16 x 30 pool forming the L. This spring has been bone dry in the northeast. We are in upstate NY. Please any advise is welcomed!!

    • Hi Eleanor
      Sounds like you have a real rouges gallery of stuff growing in your lawn. Thanks for telling me where you are located… this really helps. Since it does not sound like you want to do a total start over and to get the most for your time and money follow this schedule this spring: As soon as possible apply Turf Builder with Halts Crabgrass Preventer. In a week or so, spray your weeds with Ortho Weed-B-Gon MAX plus Crabgrass Killer. Then around Memorial Day weekend feed your lawn with Turf Builder. These three applications will not get rid of all the perennial grassy weeds that you have, however you will see a big reduction in your weeds and will be surprised at how your good grass will improve. Mow your grass at one of the higher mower settings giving you a height of 2-1/2 inches after the cut. You might consider putting down GrubEx in early June to protect your lawn as your area generally has quite a problem with grubs in late summer and fall. Then in late summer you can let me know how your lawn looks and I will tell you what to do for late summer/fall.

      • Eleanor permalink

        Thanks, I’m starting today.

  5. Eleanor permalink

    How long before we should see weeds dying out and improvement?

    • Hi Eleanor
      You will not see weeds die after applying Turf Builder with Halts. You will just see greener, healthier grass and the weed prevention will be in place. After spraying Ortho Weed B Gon MAX you will see weeds start to die in a few days and totally disappear in about 3 weeks.

  6. Eleanor permalink

    Ok so I did everything except the grub killer. We had a severely dry summer and the dirt seemed like concrete. I tried to water but couldn’t keep it wet enough. Everything turned brown. We have creeping ivy now, along with some of those grasses that look like crabgrass and some coarse, wide bladed grass. These are the 2 most dominant weeds. A few dandelions but not bad and some moss here and there. The grass has greened up again with the cooler weather and some rain now and then. What should I do next?

  7. Hi Eleanor
    Based on the fact that you live in upstate NY, you still have time to feed your lawn Turf Builder WinterGuard. This will help your good grass build a stronger root system. The crabgrass will die with the frost. Suggest you spray your ground ivy with Ortho Weed B Gon MAX plus Crabgrass Killer. Since you are in an area that typically has lots of grub problems, be sure to put down GrubEx next May or June. Good Luck

  8. David permalink

    I noticed that when I remove a course fescue clump, it will leave a recess or at least a divet in the lawn. I have been filling the space with top soil to raise the level to the rest of the lawn. Of course, this makes the job more expensive and a lot more work, since I have to buy and move the topsoil. My question is that filling these lawn indentations is overkill, is this additional step necessary.

    • Hi David
      I understand your situation completely. You could skip filling in the “hole” left by the tall fescue clump, however your mowing would be rough and bumpy until the soil starts to slowly migrate into the hole from the sides. Your approach to fill the holes to smooth out the lawn makes for easier mowing and lessons the chance for kids stepping into those pockets when running across the lawn. It also provides a soil zone for the surrounding grass plants to spread with new grass plants. Kentucky Bluegrass is capable of sending out roots that form baby grass plants in those new areas.

  9. Francis David Moore permalink

    There is a product called tenacity which kills nimblewill without killing the grass.

    • Hi Francis David Moore
      Thanks for passing along this info. This active ingredient is in Scotts Starter Lawn Food for New Grass plus Weed Preventer. Here is a link to product info: Nimblewill is not listed on the label, however you are correct it is listed on some products that have this active ingredient for post-emergent, not pre-emergent control of young Nimblewill (may take repeat applications). They suggest using a special surfactant mixed with the spray.

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