Below I present what are considered some of the best crabgrass killers, as well as two of the lower-grade post-emergent herbicides that are more readily available to the general public. I also explain how to use these products. But a major takeaway from this article should be that killing, per se is not the optimal control method.
If you're a sports fan, just think of the adage, "the best defense is a good offense." Crabgrass is opportunistic and generally becomes a problem in lawns only where there are bare spots and/or compacted soil. Eliminate these opportunities for a weed invasion and you probably won't have to concern yourself much with herbicides.
But assuming you don't enjoy this ideal situation in your landscaping, let me help by acquainting you with crabgrass killers.
Pre-Emergent Crabgrass Killers
In a sense, the second best crabgrass killer (that is, after having lush grass) is also not a killer, per se. That is, you're not waiting around for the weeds to emerge and then killing them. I'm talking about pre-emergent herbicides, which are applied in spring. I discuss them in detail in my article on how to get rid of crabgrass.
Essentially, pre-emergent herbicides form a barrier across your lawn that prevents crabgrass from germinating in the first place.
Talk about nipping a problem in the bud! If you can discipline yourself to put down a pre-emergent herbicide at the right time every spring and take care of your lawn properly, you should never develop a serious infestation of this grassy weed.
To Err Is Human
Some of you may be familiar with the Prilosec OTC ads with Larry the Cable Guy.
In these commercials, Larry explains that, if heartburn sufferers take this product, they won't get heartburn in the first place. The concept makes sense: wouldn't you rather stop a problem from arising in the first place, rather than dealing with it after the fact?
But whether it's using Prilosec OTC for heartburn or a pre-emergent crabgrass killer for crabgrass, there's just one problem. "An ounce of prevention is worth a pound of cure" sounds wonderful, but we humans are often too busy, too lazy or too dumb to apply that "ounce" when we need to. Consequently, there will always be a need for after-the-fact products.
Enter post-emergent crabgrass killers. This is what you may end up using if you've neither kept your lawn lush and healthy nor remembered to apply a pre-emergent herbicide in spring.
Dealing Out Death Indiscriminately
There are both selective and non-selective post-emergent herbicides. The latter will kill everything, including the good grass that you wish to keep. An example is glyphosate (brand name, Roundup). When might you want to use such a product?
If your lawn is so overrun by crabgrass that the situation has gotten out of control, you might want to start a new lawn from scratch.
To begin such a project, you might want to kill crabgrass, grass and all in one fell swoop. Roundup would be one of your chemical options for this task. Note, however, that there are also organic ways to get rid of grass, especially if you'd prefer to dispense with a lawn altogether and plant a garden, instead.
Let's assume, though, that your lawn is not in such dire straits. In this case, what you'll want is a selective post-emergent herbicide. The question then becomes, Which one? When you've answered that question, the next one will be, How do I use it? I answer these questions below.
Best Crabgrass Killer in the Post-Emergent Group
The consensus seems to be that Drive XLR8 (active ingredient, quinclorac) is the best crabgrass killer among the post-emergent herbicides. Buckeye Turf (Ohio State University) is among the chorus of voices singing its praises.
The University of Arkansas (see link under Sources below) also lists it, along with some of the other best choices, which include Dimension and Echelon.
So you should run out and buy some Drive XLR8, right? Unfortunately, it's not that easy. In states such as Connecticut (CT), Drive XLR8 is listed as a restricted-use herbicide. That means only licensed professionals can buy it (although it would not surprise me if some people try to get around the restriction through online purchases).
So now what? Well, you could hire a licensed lawn care company to do the job for you. Alternatively, you could take your chances with one of the consumer-grade products. I tested two of them, with approximately equal (and tolerably successful) results:
- Ortho Weed B Gon Max Plus Crabgrass Control
- Spectracide Weed Stop for Lawns Plus Crabgrass Killer
For my test, I bought these herbicides in RTU form (ready to use, i.e., the product comes in its own spray bottle), but to cover wide areas, you'd want to buy the type that you screw right onto your garden hose.
How to Use Post-Emergent Crabgrass Killers
Firstly, you'll find that each particular product that you look at in this group is intended for use only on particular types of grass. Read the label instructions to see if it's meant for your type of lawn. Otherwise, you could end up harming the good grass in your lawn.
In fact, the injunction to follow label instructions carefully pertains to the whole process of applying a post-emergent crabgrass killer. But here's some advice that generally applies when using these products:
- As with pre-emergents, timing is critical. They work best on young, actively growing crabgrass plants. That typically means a portion of the June-July period.
- Prior to application, water lawn (if soil is dry) and mow (if lawn grass is high)
- Apply only if no rain is in the forecast for next 24 hours
- Using a surfactant (see sidebar below) is often recommended
- Wait at least 2 days before mowing after applying
Crabgrass is considered a grassy weed, as are some types of tall fescue.
But there's another group of common lawn weeds as well. These are the broadleaf weeds. Different post-emergent herbicides exist for these two distinct weed classes (although Drive XLR8 also kills some broadleaf weeds). I include some of the most frequently encountered broadleaf weeds in my article on common lawn weeds.
Want to avoid all this hassle? Well, there's still some work involved, but, as I said above, the best method to control crabgrass is to prevent it from rearing its ugly head to begin with. Pre-emergent herbicides will help you accomplish that. But on a more fundamental level, you need to ensure that your lawn grass is healthy enough to crowd out crabgrass. In addition to watering properly and providing good drainage, focus on:
- How you mow your lawn
- Overseeding the lawn as necessary
- Fertilizing your lawn properly
- Dethatching the lawn