Optimum Control of Crabgrass

Hello Turf-Tenders!

This cloudy weather is really annoying. I need sunshine! I saw some stats on February–only 4 days of sunshine! March isn’t much better, damnit.

OMG, the forsythia are blooming! The forsythia are blooming!

Forsythia Bloom

Don’t panic! You’ve got LOTS of time, folks! There is a lot of misinformation regarding the best time to apply your crabgrass prevention product. It’s understandable because all the LCO’s (lawn care operators) are making their first applications and posting signs. The hardware stores have huge piles of their crappy retail products.

I’ve been monitoring the soil temperatures on the southwest exposure of my lawn, in an area of decent turf. Last week when it hit 73 degrees, the soil temp at 2 inches was only 46 degrees. Today it’s back down to 39 degrees. Crabgrass is considered to be a warm season annual. It germinates at 55 degrees. The forsythia bloom has turned out to be a reasonably accurate phenological indicator for crabgrass emergence, but it’s the END of the bloom, not the beginning. So relax!

When you see farmers in the fields planting corn, that’s a better indicator!

So why are the LCO’s applying their product so early? It’s simple. First, it’s a money-maker. Second, most good companies have a lot of properties to cover, so they go out early and make a Round 1 treatment, but it’s soooo early that they really need to return around May 1st and make a second application, in order to provide you with season long crabgrass control. A lot of companies won’t make a second application though. Many wait and see if they avoid it, based upon rainfall and temperatures. Warm and rainy weather conditions enhance the breakdown of the product via microbial activity. Cool and dry conditions extend the life of the herbicide.

Try to avoid the Scotts product line because those contain way to much nitrogen for cool season turf in the transition zones, like STL. Try to avoid products using pendimethalin as the active ingredient. It’s an older generation product and doesn’t have the longevity on the soil surface like prodiamine (Barricade) and dithiopyr (Dimension).

If you have a great lawn you don’t have much crabgrass pressure. April 15th is usually a great time to apply a product with Dimension. For those of you with thin or weak turf, make two applications of crabgrass herbicide. You can use Barricade or Dimension early, up to April 1st, and then make a second application of Dimension by mid-May at the latest. The second application should be Dimension, because it will actually kill young crabgrass seedlings that may have escaped your first application. It will kill small seedlings up to 3/4 inches tall! Most LCO’s don’t even know this.

It is imperative that your product contain 12% or less nitrogen! Too much nitrogen in the spring causes excessive leaf growth, at the expense of the root system. That means a lot of crappy turf in August.

There are other posts on my website that discuss crabgrass control. Go get urself edecated…type “crabgrass control” in the search bar!

Best to you,







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7 thoughts on “Optimum Control of Crabgrass

  1. The last 3 years I tried two different lawn maintenance companies to beautify my long neglected lawn. Things looked great in the spring but by July, the desirable turf suffered from brownspot (probably had to do with over fertilization) and then the nutgrass quickly took over. The result was my lawn looking worse than ever. After calling them, they told me they could fix it – for a price that doubled the cost of their yearly plan. I didn’t bite so I’ll need to get up to speed on my own treatments. One positive of have their service was the wild violets there were taking over are almost completely under control now.


    • Hello Don! Have you read the article on Brown Patch? It’s long on details and based upon your brownspot statement it would be a great review for you. If you are going to have other companies tend you turf, the time to switch to a new company is IN THE FALL! Step One should actually be the first nitrogen application in September and aeration and overseeding (if you need it). The best company in St. Louis by far is THE Turf Plan. Ryan and Dowco are also good companies. Avoid Greenscape/Chemlawn and Kapps. Thanks for the comment!


      • I need to re-read that article on bownspotting. The 2nd company did the aeration and overseeding in the fall and by spring, the lawn look great! But as soon as the weather warmed up in late June and early July, the brownspot wiped out all that effort and expense over about 1/2 my lawn. I live in the Meramec Valley in Eureka We have very heavy dew almost every night. The heat and humidity were idea for the growth of the fungus causing the brown spots. It also appeared to be ideal conditions for nutsage which rapidly filled in the brown spots. Neither of the local companies I hired said a word about how bad things turned out till I called them and asked them to cease and desist! Then is when they offered to address the problem for an additional fee that was very close to a full year of their treatment service. Being retired, I opted out of that proposal.


      • Hello again, Don! It sounds like you need to apply a product that can significantly ward off the disease called Brown Patch! There’s a granular product called Headway G that you can purchase, and it works. But it’s expensive. You need to start your applications BEFORE the onset of the disease, which is usually mid- to late May. One bag treats 10,000 sq ft. Make applications at least every 4 weeks when the humidity is high. Nighttime temps of 70 F or higher are the most significant driver of the disease. Your “bowl” description is insightful! Heavy dew promotes disease development. If you have an irrigation system, set it to come on every morning for about 2 minutes, to wash the dew off. Time it 30 minutes before sunrise.

        Nutsedge control is easy with any of the halosulfuron products, with brand names like Sedgehammer, Nut Buster, ProSedge. If you can’t apply it yourself, you’ll need to make sure you hire a GOOD LCO (as per my first response).

        Keep me posted,


  2. Thanks for your help. I’ll try to treat the brown spot and see how it goes using one of the products you’ve mentioned. I’ll let you know how the summer goes.


  3. Jeff,
    Every summer I get a lot of lespedeza, It seems to get worse every year. What is the best way to control it and if there is a pre-emergent when does it need to be applied?
    Also, I am a do-it-your-selfer and was wondering what local companies sell some of the turf products (grass seed, fertilizer, pre-emmergents etc.) you recommend on your site.


    • Hello Mach5,
      There aren’t any good PRE products to control legumes, like white dutch clover, black medic and your lespedeza. Are you sure it’s lespedeza? You’ll need to spray it with any of the hose-end products that contain dicamba. Read the active ingredients to be sure. Buy the one that’s on sale, no matter the color (brand) of the bottle! Spray twice, about 21 days apart.
      The places that sell the best products are THE Turf Plan in Ellisville, and GR Robinson Seed and Service, in Olivette. Please tell them I sent ya!

      And shoot me a photo of that weed, to jefftravers58@gmail.com.

      Best of luck,


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