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Crabgrass Prevention – Timing is Everything

February 16, 2012

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.

Apply crabgrass prevention before yellow blossoms fall from forsythia bushes.  Note:  After this very tough winter, your forsythia may not bloom as much as usual.  If that is the case, apply before you see lilacs bloom.

Apply crabgrass prevention before yellow blossoms fall from forsythia bushes. Note: After this very tough winter, your forsythia may not bloom as much as usual. If that is the case, apply before you see lilacs bloom.

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

To feed your lawn and prevent crabgrass apply Scotts Turf Builder HALTS Crabgrass Preventer with Lawn Food. (If you have dormant Bermudagrass, Zoysia or Centipede grass that is less than 60% green coming out of winter, 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 Lawn Food for New Grass Plus Weed Preventer.

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

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  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 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.


    • 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?


    • 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,


    • 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).


  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


    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.


    • 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.

  10. Vic permalink

    i put down scotts turf builder halts crabgrass preventer about 2 weeks ago and now my lawn is infested with dandelions. All my neighbors hire a company to fertilize their lawns and now one else has dandelions. What do i do?

    • Hi Vic
      Since your feeding of Turf Builder with Halts Crabgrass Preventer will continue to feed for about another 5 or 6 weeks, you do not want to put down Turf Builder Weed & Feed to kill your dandelions yet. However, you can kill your dandelions and other weeds without hurting your good grass with a product that does not feed: a spray of Ortho Weed B Gon MAX plus Crabgrass Killer will kill your dandelions.

  11. Judy permalink

    Besides crabgrass, I have other weeds, lots of dandelions and others. Do I need an additional weed killer after I apply for crabgrass. Also when can I over-seed after these applications

  12. It’s feb 2 in Long Island ny can I put crabgrass preventer down now so I can seed in april

    • Hi Cw
      If you put down a typical crabgrass preventer now you will not be able to seed in April as the crabgrass prevention barrier will be active on the soil. Since crabgrass germinates in your area in early April the same time you seed, I suggest you use a special crabgrass preventer that will prevent crabgrass but not your grass seed from germinating. Scotts Starter Lawn Food plus Weed Preventer would be a better choice.

  13. Pat Grant permalink

    I had problems with crabgrass last year. I may have put down halts too late. I just bought a soil thermometer. What temp am I looking for?

    • Hi Pat Grant
      The soil temp needs to hit 60 or so for a few days for crabgrass to germinate. this will happen faster on a south facing slope or next to a sidewalk. It is ok to be a little bit early with your application. Be sure to water after spreading or spread prior to a rain to help create the prevention barrier.

  14. Brenda permalink

    I just put down Scotts weed & feed with dandelion clover weed killer, is it too late for me to apply Scotts with Halts Grabgrass?

    • Hi Brenda
      Since Turf Builder Weed & Feed (which you already applied) and Turf Builder with Halts Crabgrass Preventer (which you want to apply) give a feeding of Turf Builder, the minimum time to wait between applications (feedings) is 4 weeks. Another option is to apply Scotts Halts Crabgrass Preventer now (the one that does not contain Turf Builder) so you get the weed prevention down before it is too late.

  15. Steve permalink

    Hello, new to lawn care last season we lard all new sod . We put down milorganite down mid April. Just noticed the crabgrass coming up last week of April. We are in end of first week of May and weather has been much colder I the 40s at night. Can I still put down crabgrass preventer or is it to late? Already spot treated crabgrass with ortho crabgrass killer

    • Hi Steve
      Crabgrass will continue to germinate over the weeks ahead. An application of Turf Builder with Halts OR Halts (without the Turf Builder) will help prevent those seeds that have not germinated yet. Be sure to water after spreading to set the prevention barrier as quickly as possible.

  16. Rhonda permalink

    Can you put weed and feed down down at the same time you put halts down?

    • Hi Rhonda
      Typically one would wait a week between these two applications. If you are spreading Halts without the Turf Builder in it, a week will work out just fine (since you are only putting down one feeding with the Turf Builder Weed and Feed. Remember that Halts needs to be watered after spreading and weed & feed needs to go down on moist foliage without any rain forecasted or irrigation for 24 hours. Also, Halts should go down ASAP and the Weed & Feed needs to go down when weeds are actively growing (your daytime high temps should be regularly in the 60’s or higher).

  17. David Nelson permalink

    Does the crab grass preventer interfere with over seeding? It works by preventing the crabgrass seed from germinating?

  18. Floyd Corley permalink

    I have a small lawn about a quarter of an acre. I sprayed it with Roundup to kill everything a few weeks ago and used a machine to slice and groove it up, and limed it, and put Scott’s Starter Lawn Food, and sowed tall fescue. The new grass is up about an average of two inches high in most places, although I did sow more seed in thin places. I still have not mowed this 2 inch high new grass. I have a 40 lb. (15000 sq. ft.) bag of Scott’s Turf Builder Halts Crabgrass Preventer with lawn food. Should I go ahead and put this on now, or wait for this new grass to get up to 3 inches, or higher, and mow it. I don’t want to wait too late to put this on and let the crabgrass seeds sprout out, but I don’t want to damage the new grass either.

    • Hi Floyd Corley
      Turf Builder with Halts should not be applied to newly seeded grass until after the new plants have been mowed 4 times. You can mow your new lawn when it grows another inch or so leaving it at around 2-1/2 inches after the cut. You could put your Turf Builder with Halts down after 4 mowings as there could be crabgrasss germination into early summer. If you see any stray crabgrass plants that germinate before you have been able to prevent them, you could spray them with Ortho Weed B Gon MAX with Crabgrass Killer after your grass has been mowed 4 times. If you give me your location, I can give you a better idea when crabgrass germinates in your area.

    • Bob W permalink

      Scott’s has a fertilizer that has crab grass preventer and is safe for new seed, Scott’s starter lawn fertilizer plus weed preventer. It prevents dandelions and crab grass on newly seeded turf. I’d try that. I’m not sure about the regular spring fertilizer with halts.

  19. Hi Bob W.
    Thanks for your helpful suggestion. Scotts Turf Builder Starter Lawn Food plus Weed Preventer is best applied the same time as seeding prior to the first time you water the newly seeded area. There may be some temporary white discoloration of the existing grass that is already growing.

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