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Crabgrass Prevention – Timing is Everything

February 16, 2012

Apply crabgrass prevention before yellow blossoms fall from forsythia bushes

Crabgrass seedlings sprouting in early spring

Don’t be one of those lawn owners who “wonder why they have crabgrass in summer even though they put down crabgrass preventer in spring”.

Most weed prevention failures relate to making the application too late to prevent those pesky crabgrass seeds from germinating (more about this later). I should also point out that sometimes folks think their weed preventer failed because they do not understand that weed preventers are designed to stop “annual” weeds (like crabgrass, foxtail, barnyardgrass, spurge, etc.) from germinating, but not “perennial” weeds that grow back from their roots (like coarse fescue, orchardgrass, quackgrass, nimblewill, etc.) Back to timing… be sure to apply your preemergent weed control before crabgrass and other annual weeds germinate.

So how do you figure out when is the best timing to apply your pre-emergent weed control? Crabgrass needs soil temperatures in the 60’s for about a week to begin germination. Since most of you probably do not have a soil thermometer, the next best indicator that conditions are right for crabgrass germination are the plants in your neighborhood. Apply before the yellow blossoms fall off the forsythia bush (see photo), or by the time you see lilacs in bloom, or before you start seeing dandelion puffballs.

The next question you may have is what product do I apply to prevent my crabgrass and other summer annual weeds?

If you have St. Augustinegrass, you need to apply Scotts Bonus S which not only provides weed prevention, it also controls actively growing weeds in your lawn. You should plan on making two applications this spring about 6 to 8 weeks apart. If you want to also kill and prevent Fire Ants in your lawn, you should go with Scotts Bonus S MAX instead.For other lawn types you should apply Scotts Turf Builder plus HALTS. (If you have dormant Bermudagrass, Zoysia or Centipede grass you should use Scotts HALTS without the Turf Builder.)

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

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

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18 Comments
  1. Gene Krieger permalink

    I have an infestation of a very course grassy bunch grass that has come up where the septic tank drain field was put in. It plugs my mower deck. Could I send you a sample plant to identify. I need to get rid of this and not lose the scotts I planted last fall. Help!! Gene

    • Hi Gene
      There are a number of perennial grasses that look like your description including Tall Fescue, Orchard Grass, and Timothy Grass. You would have to dig these out or spray with RoundUp when they are actively growing (being careful to not get the spray on your good grass). Sometimes when a contractor does a seeding in an area like you described, the seed blend contains Annual Ryegrass to provide some fast temporary cover while the more desireable perennial grasses are germinating and becoming established. This Annual Ryegrass then dies out during the first hot summer. The plant is clumpy and the blades are wide and the underside of the leaf is very shiny. If I have not helped you figure this out, you may get ID if you are able to email a couple of good pictures to customer.services@scotts.com Make sure the email file size is not too big (over 7MGB) or it will not be received.

  2. Bob W. permalink

    Hi Ashton.

    I live in Columbus, Ohio. I put down scotts with halts on Saturday(soil temps have been between 60-65 degrees) and there was a gentle rain on saturday night and sunday morning. It was nice here for most of the day on Sunday and then we got hit hard with buckets of rain. I mean we got a lot of pouring gushing rain. Anyway, I am concerned that what I put down may have gotten washed away. Would the first light rain have been enough to have the fertilizer and halts in the soil? What are your thoughts on this?

    Oh I know how you have posted the soil temp map in the past. It seems that they changed the link a little bit but I found the new one!! Here is the new one. http://www.greencastonline.com/tools/SoilTempMaps.aspx

    Thanks!

    • Thanks for sending along the new link Bob. I think your crabgrass preventer will still work. Since it got watered in, I would not expect you to see a total crabgrass barrier breakdown unless the gusher was so heavy that you actually experienced soil eroision. Good luck with your lawn.

  3. Ashton:

    I live in Nashville, TN. I put crabgrass preventer out today (December 30th). After reading various articles, I’m concerned that I put the preventer out too early. What do you think?

    Phillip

    • Hi Phillip
      Even though you put down your crabgrass preventer earlier than recommended, you will get some prevention of spring germination. Your crabgrass barrier may run out of gas prior to any summer germination however. If your lawn is thick and you are mowing at a higher setting (around 3 inches for fescue) this will help limit summer germination. If you have bermuda mowed at a shorter height or if you get some lawn thinning from drought or other damage this summer, you may get crabgrass germination. You have two choices: First, if you have had a really bad crabgrass problem in the past you might consider a follow up application of Halts in late April/early May. Second, if your crabgrass problem has not been severe in the past, you may have some Ortho Weed B Gon MAX plus Crabgrass Killer on hand to spray young crabgrass plants as you see them. Good Luck with your lawn and Happy New Year!

  4. john permalink

    Hello, I live in Dayton, Ohio and this past fall, I bought some Scotts tall fescue grass seed and planted it andit is now established but unknow to me, I used a bale of straw to cover it when I put down the seed, now I have somekind of tall grass that looks exactly like the seedlings of wheat and I did noticed that there were alot of those round large seeds were in the straws when I put them down in the fall. so now how do I kill those wheat plants among my new lawn? will the wheat grass die on their own when tempurature get hotter ? since tthey survived the winter cold.

    Please help!

    • Hi John
      You are likely looking at wheat. As you mow your grass this spring, it will thin. By summer it should be gone. If there were some perennial grasses growing in the wheat field and they ended up in the straw, you may have to deal with them later. However, most framers keep their wheat fields pretty clean these days. Good luck with your new lawn.

  5. Paola permalink

    We put out Haltz on our St Augustine grass back in February and again 8 weeks later (we live in FL) yet we still have crabgrass seedlings. What should we do now?

    • Hi Paola
      Sorry to hear about your crabgrass problem. Sorry, I do not have a spray to recommend to kill crabgrass in your St. Augustine grass. If you live in South Florida, you may have crabgrass that does not die out in winter, so it acts more like a perennial rather than an annual. One suggestion would be to put down Halts in January, then do two applications of Bonus S… first in Feb or March (depending on where you live) and then the second about 6 weeks after the first. The other suggestion is to get make sure you are dealing with crabgrass by getting an ID at your local Cooperative Extension office or at a Garden Center. Hope this helps.

  6. Hello Ashton and thank you in advance,

    I live in St. Louis and we have a Zoysia lawn. I am a recent transplant from NYC so I have never had a lawn before (please be gentle). I would like to do some basic care myself and I was wondering if you had an idiot’s guide what what to do when for a healthy lawn.

    Thank you,

    dp

    • Hi dpbklyn
      I am assuming your Zoysia is fairly weed free and you want to know how to care for it. Feed your Zoysia with Turf Builder or GreenMAX when you see about 50% green growth this spring and then continue feeding at 6 to 8 week intervals for a total of 4 feedings this year. Also, put down GrubEx in May and Ortho Bug B Gon in Late June. If you get some weeds during the year, you can spot treat them with Ortho Weed B Gon MAX. That should do it! Good Luck with your lawn and your move to St. Louis!

      • Thank you for the reply!

        We are having someone come and de-thatch next week, it seems to have been years since it was de-thatched. He suggested we put down some crabgrass barrier (HALTS).

        Does this make sense, or is it a waste of time? Would you recommend HALTS or the HALTS with food (I forget what it is called).

        dp

  7. Hi dpbklyn
    It is a great idea to put down Turf Builder with Halts after dethatching. If you need to seed, do not put down Turf Builder with Halts in those areas. The crabgrass preventer that will not keep your new grass seed from growing is Scotts Starter Lawn Food for New Grass plus Weed Preventer.

  8. PLewis permalink

    Hi,

    I applied Scotts Turf Builder with Halts Crabgrass Preventer and Lawn Food in April. I live in Buffalo NY, long winter.

    A few weeks later, when clover weeds started to come in, I probably over used Round Up spray and killed a lot of the grass around it.

    Now I have a lot of dead/yellow areas of lawn.

    Is there anything I can do at this point? Without having to wait until Sept.

    Thanks.

    • Hi PLewis
      Sorry to hear of your situation. The directions for Turf Builder with Halts indicate you can not seed for 4 months after application, even though you could seed one week after spraying Roundup in an area of your lawn. If you have small areas you may be able to break up and dilute the crabgrass prevention barrier enough to allow seed to grow by breaking up the top two to three inches of soil and mixing in some Scotts Lawn Soil organic matter prior to seeding. This would not make sense in a large area, so fall would be the best opportunity. In the future there are several Ortho Weed B Gon products that will kill clover without killing your good grass: Chickweed and Clover Killer and Weed B Gon MAX plus Crabgrass Killer.

      • PLewis permalink

        Thank you for your reply. The area is only roughly 250 square feet so I am going to till the area., mix in Scott’s lawn soil and lay sod over it.

        I will let you know how it works. If you have any other tips, let me know.

        Thanks again.

  9. Hi PLewis
    After you sod, spread Scotts Starter Lawn Food for new lawns on your new lawn.

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