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My backyard is being overtaken with crabgrass again. It started later this year than last. In the early spring, I rented a de-thatcher/powerrake and cleaned up the year of a lot of dead material (to promote growth of "regular grass"). I also applied "Dimension" twice — once in early March and again in mid April (following a local landscaping suppliers recommendation). I did not powerseed last fall or this spring.

I live in Southern New Jersey (United States). 2010 Spring/Summer were brutally hot/dry. This (2011) spring/summer have been much more "average" in temperature/precip. I just treated with the Summer Scotts fertilizer mixture (early July). The backyard is on a small slope, but definitely not dramatic — perhaps an elevation change of ~6–8 feet over ~90 feet. The yard has little in the way of shade (mostly full sun from about 10am–6pm). The lawn is otherwise healthy. In fact, up until about 3 weeks ago, it was covered in what appeared to be a green/healthy grass.

Question: Is there any way to rapidly remove the crabgrass (organic or not), and do this in a way that will not harm any of the "good" grass that currently exists at this point in the season. For example, a chemical/product/etc that I can apply that will only kill off the crab grass, such that I don't have to manually dig up all the crab grass roots (and rip out "good" grass roots at the same time)?

There is this other question on how to prevent crabgrass from growing, but I'm mainly interested in removing existing crabgrass from my lawn.

In addition, any tips/advice/product for preventing crab grass emergence next season are appreciated and/or any details on why this year's pre-emergent (Dimension) application may not have worked would be helpful.

Update: Here is a picture I snapped of the "infestation". enter image description here

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First, I was going to post a similar question, as I would also love to be made aware of a magic bullet for dealing with crabgrass.

I'm guessing, I have fairly similar (weather) conditions as yourself, but even hotter & humid summers = Mid-West (St Louis Missouri).

Now let me get this "bad" piece out of the way, and I mean no offence by it, it's just my personal opinion, approach to lawn care:

Short of digging up all the crabgrass, are there any options for safe removal at this point in the season (where average daytime highs are now in the 90s)?

  • "Dimension" I'd not heard of that, so looked it up on line. It is not an organic product from what I can tell (please correct me if I'm wrong on this), therefore I wouldn't call it a safe option. One of the active ingredients in "Dimension" is Dithiopyr (used as an preemergent herbicide used to prevent crabgrass seeds from sprouting in the spring).

  • "Summer Scotts fertilizer mixture", again I'd not heard of that specific product, but knowing what I do at this precise time (not a lot), very! few Scotts products available to the "general public" are organic, therefore I wouldn't call it a safe option, unless I'm corrected on this and told it is an organic product.

Now that the "bad" piece is out the way (again I hope I didn't cause offence with my above mini-rant).

Here is what I do in my organic lawn, crabgrass battle:


While I fully realise the above does not give you a "magic bullet" for dealing with crabgrass, I hope it does proves somewhat helpful.

Good luck, and please let me know if you find that "magic bullet."

  • What I mean by "safe" is -> if I apply products like Dimension when it's 90+ degress and full sun, then I'll likely "burn" the good gradss. – Brian Jul 20 '11 at 18:01
  • Brian, without a doubt you will experience some burning on your lawn when applying such a chemical based fertilizer in those kind of weather conditions. Me, being me, those type of chemical based fertilizers aren't safe... – Mike Perry Jul 20 '11 at 18:10
  • Up voted as very good information and good link to organic lawn care guide. I think I am guilty of too frequent watering. I also have to get the soil tested to know where I stand. – Brian Jul 20 '11 at 18:19
  • @Mike: Wow, thanks for the detail. I'm preparing to do battle with crabgrass on a large scale. How many square feet are you applying your 5g tea treatment to? – bstpierre Jul 20 '11 at 20:52
  • bstpierre, I spread via a watering-can the 5 gallons of Compost Tea over approx 1800ft² (170m²). Lawn area is about the same front & back for me. So one week the front lawn gets treated, then the following week the back lawn gets treated, repeat, repeat... – Mike Perry Jul 20 '11 at 21:10
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Believe it or not, baking soda does the trick. It is usually best to spot treat as soon as you see some crabgrass as it spreads very fast. Especially in the hot summer. You still have to pull the dead crabgrass root and all once it dries out or it WILL come back.

Crabgrass is the bane of my existence and I have fought this losing battle for many years now. Once it gets too out of control, I usually wind up digging the patches up. Good grass and all. Wish there was a better way. It drives my wife crazy, but what drives me even crazier is to replace the entire lawn when it does get out of control. I have asked professionals about this and the only thing that was mentioned was a product called azulux and then they said while it's effective you still have stay on top of the situation. Very expensive as well. Last I heard it no longer for sale to the general public. Not sure though Tips like deep watering and keeping your grass longer when it's hot make sense but in the hot summer the crabgrass usually takes over so stay on top of it to get rid of it. Hope this helps. Just my two cents.

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Have no fear my friend, I have your solution: Tenacity

I have been able to battle the horrible lawn in my foreclosure, located in Ohio, with weed-b-gone fairly well. Winning that battle, along with dormant overseeding with the wet springs here, I turned my lawn into a gem of the subdivision. However, the crabgrass and quackgrass is nuts. The big box store herbicides were just not cutting it, but then I found this new product. It is cleared for residential use now and it appears to be safer to animals and the environment being it is a synthetic version of a chemical found in bottlebrush plant. It prevents unwanted turf grasses from producing chlorophyll, thus starving.

I have had amazing results with this stuff. I found it at a local John Deere Landscaping store here for $50 per 8 oz bottle which is 48 gallons for spot treatments. WAY cheaper than buying gallons of inferior products elsewhere. This comes highly recommended. It has taken care of my quackgrass (you think you got issues with crabgrass, think again), nibbleweed, bentgrass, and poa annua infestations in my yard with this stuff. It is truly a revolutionary product that I expect to turn the industry on its head.

Neighbors have told me that my lawn was out of control for several years as the old owner gave up on life, so with the amount of crabgrass seeds in my lawn, I have given up on the pre-emergent angle and I figure I will let them all germinate over the years and then kill them as they do so.

Edit for photo request:

I only spot treated a few small spots in my yard about 5 weeks ago. Those weeds have died and dried up. The quackgrass has come up again (deep, deep rhizomes / nasty stuff) but it has diminished. After a few rounds, I expect to eradicate it. I spot treated my entire lawn (7,000 sqft) with 2 gallon of this stuff. These photos are showing the 4/5 day mark. They are starting to turn white, while the turf grass of Kentucky Blue Grass and Tall Fescue is fine. The bleach white clover looks pretty neat actually. I thought the large patch of grass growing with above ground stolons was Bent Grass, but now I think it is Nibblewill. This stuff is working great on it.

Crabgrass Clover Nibblewill Quackgrass

If you do some research on this new stuff, professional landscapers are rejoicing. Not only do they not have to kill the entire area for lawns with Quackgrass, then come back for a second time to seed, they can just spray it and be gone. Customers like it because the white weeds make it really show how the weed "killer" is working.

  • I've read about Tenacity. Many folks on lawn sites use it religiously, so I figure it works as you say. A very useful answer in my opinion! – Randy Aug 2 '13 at 14:59
  • Tenacity link is dead. – mxmissile Feb 15 at 15:02
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I brought an Ace product that kla crab grass and you can use it below 90 degrees. After 3 days and two applications, connect to hose, my crab grass is drying up and dying. Kills to the ROOTS!!

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    Does "Ace" mean Ace Hardware? Is it a store brand of crabgrass killer? – Niall C. Jul 28 '13 at 1:07
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No. There are no post-emergents that specifically kill crabgrass without killing lawn grass. Spray and pull to kill existing grass and use pre-emergents in fall and early spring.

  • False. See my answer. – Evil Elf Jul 29 '13 at 13:08
  • Fair Point. Never heard of Tenacity. Thanks for letting me the community, me included, know. ...Looking online, it's expensive stuff. Though, if it does what it says it does, Tenacity is a cost effective solution. – user446 Aug 1 '13 at 17:59
  • I used it to spot treat until last week. I sprayed my entire lawn. It is amazing. There is something really neat about bleach white clover. It is actually pretty before they die. This stuff is going to take over the industry IMO. – Evil Elf Aug 1 '13 at 19:57
  • Evil Elf, if you have any photos, can you try and post them? It's not that I don't believe you. I'm just damn curious. thnx. – user446 Aug 2 '13 at 5:27
  • It is not really expensive IMO. $50 for a 8 ounces. That makes 48 gallons of solution to spot spray. You need to add a surfactant; either a real one for $5 or use dishwashing soap. That's barely over a dollar per gallon compared to a $12 gallon of weed killer. If you have a larger lawn and will use a bigger spreader, the solution is around 1/4 teaspoon per gallon I think. My neighbor wants to give me money to split the bottle. That is an option as well. – Evil Elf Aug 2 '13 at 12:34

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