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When to Prevent Crabgrass?

February 8, 2013

If you love your lawn, you’ve gotta hate crabgrass.  It’s an aggressive, stubborn weed.  Even if you had only one crabgrass plant last year, your lawn could have thousands of crabgrass seeds lying in the soil right now ready to grow up and choke your good grass to death. But you can put a stop to crabgrass and other annual grassy weeds like foxtail and barnyardgrass before they get started by putting down the right preventer.

The big question:  When to apply?  Experts say crabgrass germination starts when your soil temperature reaches 55 degrees for several days. Since most of you probably do not have a soil thermometer, here is a link to a soil temperature tracking map that provides you up to date soil temps for your area. You can also look at a 5-day projection of soil temps for your geography by using the pull-down menu at this web site.  It is better to get your preventer down too early than too late.  (Note:  When I lived in California I learned how hard it is to use maps like this because of all the microclimate situations, so I suggest for Southern California get you preventer down now before March 1 and for Northern California before March 15.)

Another tip of what to look for in your local neighborhood to help you with your crabgrass prevention timing is the forsythia bush (see photo).

You should apply your crabgrass Preventer by the time forsythia bushes in your neighborhood have stopped blooming and lost their flowers, or if you do not have forsythia, by the time you see lilacs in bloom, or before you start seeing dandelion puffballs.

You should apply your crabgrass Preventer by the time forsythia bushes in your neighborhood have stopped blooming and lost their flowers, or if you do not have forsythia, by the time you see lilacs in bloom, or before you start seeing dandelion puffballs.

The next question is what product to apply to prevent my crabgrass and other summer annual weeds?

For the South:  You should apply Scotts Turf Builder with HALTS. (If you have dormant (brown-looking) Bermudagrass, Zoysia or Centipede grass you should use Scotts HALTS without the Turf Builder.)

For the North, Midwest and West:  For all lawns except Dichondra and Bentgrass apply Scotts Turf Builder with HALTS.

If you plan on seeding this spring, you need to use a special crabgrass preventer that is compatible with grass seed: Scotts Starter Food for New Grass plus Crabgrass Preventer.

If you have lawn questions here is a link to contact our Scotts Help Center.

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20 Comments
  1. Charles Harris permalink

    I live in Salisbury NC 28144 . Air rated and over seeded in the fall and have a number of ungrassed places in yard that need over seeded. Should I use HALTS at this time if I am over seeding> If I do, will HALTS preclude the over seeding from germinating> Thank you, I have always liked your products;Charles Harris

    • Hi Charles
      Gland you asked. Halts will prevent your grass seed from growing. If you had a crabgrass problem last year, you can use Scotts Starter with Crabgrass Preventer instead of Halts when you seed, since this will not hinder your grass seed germination. Even though this product only prevents for around 6 weeks, this can be enough time for your good grass to get established. If you did not have much crabgrass last year, you could just use Starter Fertilizer when you seed, then spray any young crabgrass plants in May/June with Ortho Weed B Gon MAX plus Crabgrass Killer. Good Luck.

  2. Janek Kruglov permalink

    Hi Ashton!

    I live in Charlotte, NC 28277. Does it matter if I apply the crabgrass preventer befofe or after cutting the grass? Is it better to apply on a dry or wet grass?

    Thanks
    Janek

    • Hi Janek
      You can apply before or after mowing. If you think you may get mower wheel tracks confused with spreader wheel tracks, spread before you mow. The grass does not need to be wet when you apply, dry grass will allow the particles to get down to the soil better than wet grass. It is best to apply before a rain so the particles get down to the soil.

  3. When is the best time to overseed and how is it done? I was going to use Halt because of all the weeds, but it looks like that will not be a good idea.

    • Hi Angela
      If you tell me where you are located I can give you a more exact answer. Grass Seed germinates about the same time as when crabgrass germinates. The map link to soil temps in my When to Prevent Crabgrass blog post may be able to help. You are right, Halts can not be used when seeding. Use our product called Starter Lawn Food with Crabgrass Preventer instead when you are seeding.

  4. jjm747 permalink

    Hi Ashton…live in East TN and have tall fescue. I plan to reseed about 2000 sq ft of the lawn this spring. Couple of questions: 1) It appears that Scotts Starter Fertilizer Plus Crabgrass Preventer has been changed…is it now called Scotts Starter Food for New Grass Plus Weed Preventer? If it is the same product, I assume you put it down the same day after you put down new grass seed? 2) I ran out of time to reseed last fall. I did manage to kill the area I had planned to reseed by applying RoundUp. During the winter the area I cleared is now over grown with weeds. I plan to reapply RoundUp to kill the weeds. When do you think would be a good time to reapply RoundUp to the area and later reseed? Many thanks for your help.

    • You can spray your weeds with Roundup after the weather warms up enough for you to see them growing. You will need to wait at least a week to seed. Break up the soil enough so the seed makes contact. You are right the crabgrass preventer that you can seed with has been updated. You still put it down the same day you seed. Good Luck.

  5. Gerri T permalink

    I plan to put down the starter food for new grass with weed preventer at the same time i sow additional seed. I also have a lot of moss in my yard so i will need to put down lime. Can i do this all at the same time?

    • Hi Gerri
      It always helps to do a soil test to determine your soil pH and how much lime is needed. (Moss is not always an indicator that lime is required… I have seen moss in shaded lawns that had a high pH with no need for lime.) Lime can go down anytime of year. I like to put it down at a different time than other products when rain is expected. So, If you think you need lime, you could put that down now and then seed after the lime has been watered in good.

  6. Jay permalink

    I seeds very heavy last September to get fall growth and the lawn was full. However, has a lot of crabgrass and dandelions that ided off and left many area thin. Should I reseed again this spring and use Scotts Starter with crabgrass preventer or just use Turf builder with Halts?

    Also, If I do use halts how long do I need to wait before any seeding? I plan to put crabgrass preventer down no later than March 15th here in Maryland.

    • Hi Jay
      If you have thin spots that are larger than 4 to 6 inches in diameter, you could seed this spring and use the Starter with Crabgrass. If your thin spots are not that large, then you could feed to help your existing new grass fill in. In that case, Turf Builder with Halts could be used. If you put down Halts this spring, it is suggested you wait until next fall to seed.

  7. Kevin permalink

    In La when is a good time to put the crabgrass preventer?

  8. Jeff in Houston permalink

    Can I apply Scotts Bonus S Southern Weed & Feed and Scotts Max Green Max Lawn Fertilizer on the same day or do I need to space out the applications (if so, how long)?

    • Hi Jeff
      Since both products feed your lawn, apply Bonus S first and then wait at least a month before putting down Green Max.

  9. Manny permalink

    Hi Jeff- I live in NJ- last Sept. we pulled all of the crab grass out of the front & back lawn by hand. Then overseeded the entire lawn. Do I need to put down Turfbuilder with halts or will that stop the germination of the good grass? I don’t want new crabgrass to come in but don’t want the new grass seed to suffer. what do I do?

    • Hi Manny
      If the grass seed you put down last fall is growing now and has been mowed at least once, you can safely put down Turf Builder with Halts to prevent crabgrass. You should do this as soon as you can. If you are going to seed some areas this spring, you need to use a different crabgrass preventer: Scotts Starter Food for New Grass plus Weed Preventer.

  10. Hello,
    This answer is a bit confusing. It seems to be the topic of crabgrass but you mention that Scotts Bonus S for southern lawns as a crabgrass preventative. I have just talked to Scotts and they say that this product WILL NOT control crabgrass. It’s good with certain southern weeds but NOT CRABGRASS. They recommend of course, Turf Builder with Halts but Bonus S for Southern Lawns will not do anything and I can attest to this here in FL. I used this product and the crabgrass is still here while other weeds have died off. This article should be amended so that it is not misleading and looks like it prevents crabgrass.

    • Hi Bart
      Thanks for your suggestion. I will update this posting to reflect the changes to the Bonus S Weed & Feed label. At one time this product was recommended for crabgrass prevention (not control). The problem is that more recently in the more southern areas of Florida and Texas crabgrass is more of a perennial than an annual. When it does not die out during winter, you can not prevent the new plants with a Jan/Feb application of Bonus S. The current label has been changed to drop the crabgrass prevention claim. Sorry for the confusion. Thanks again for taking the time to let me know.

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