How to Rid Your Lawn of Crabgrass

The Trick Is to Kill Only if You Have To

Closeup of crabgrass plant in bloom.
NY State IPM Program at Cornell University/Flickr/ CC BY 2.0

What are the best crabgrass killers? If your lawn is losing out to this common weed, then finding out the answer to this question may help you sleep better at night. Below, you will also learn the right way to use these products. But a major takeaway from this article should be that killing the weed is not really the best control method.

You might say that the best crabgrass killer is not actually a "killer," at all.

Instead, this trick simply involves having a lush, healthy lawn. Crabgrass takes advantage of lawn areas that are not in good shape, to begin with. That is its ticket onto your property. It generally becomes a problem in lawns only where there are bare spots and/or high-traffic spots where the soil has been walked on so much that it has become hard. If, through proper lawn care, you do not allow such spots to crop up on your lawn, then you will often avoid having any problem with this weed.

But assuming you don't enjoy this ideal situation in your landscaping, you may have to turn to crabgrass killers (that is, herbicides).

Pre-Emergent Crabgrass Killers: Fighting the Weed Ahead of Time

In a sense, the second best crabgrass killer (after having lush grass) is also not a true killer. That is, you are not waiting around for the weeds to emerge and then killing them. "Pre-emergent" herbicides are so called because they take care of the matter before it becomes a big problem.

They are applied in spring and basically form a barrier across your lawn that prevents crabgrass from germinating in the first place. If you can manage 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 crabgrass problem.

Why There Is a Need for Post-Emergent Herbicides

The idea just stated makes sense. Wouldn't you rather stop an issue from arising in the first place, rather than dealing with it after the fact? But there is just one problem. "An ounce of prevention is worth a pound of cure" sounds wonderful, but what if you do not have the time to apply that "ounce" when you need to? We lead busy lives. Family and career duties often keep us from giving our grass the preventive care that it ideally needs. So 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.

Selective vs. Non-Selective Products

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, lawn grass, and all in one fell swoop.

Roundup would be one of your chemical options for this task. But for those who think that it is healthier to stay natural, note that there are also organic ways to get rid of grass.

Let's assume, though, that your lawn is not in such bad shape that you will want to get rid of it entirely and start all over. In this case, what you will want is a selective post-emergent herbicide. "Selective" means that it will not kill everything that comes across its path, just targeted plants. The question then becomes, Which one should you buy? When you have answered that question, the next one will be, How do you use it? These questions will be answered below.

Best Crabgrass Killer in the Post-Emergent Group

The consensus is that Drive XLR8 (active ingredient, quinclorac) is the best crabgrass killer among the post-emergent herbicides.

The University of Arkansas lists it among the best choices, which also include Dimension and Echelon. 

So you should run out and buy some Drive XLR8, right? Unfortunately, it is not that easy. In states in the U.S. such as Connecticut, Drive XLR8 is listed as a restricted-use herbicide. That means only licensed professionals can buy it (although it should not surprise us that 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, since they would have access to Drive XLR8. Alternatively, you could take your chances with one of the so-called "consumer-grade" products. This means that they are not quite as strong, but that the average person can buy them easily, since home improvement stores commonly sell them. The author tested two of them, with about equal (and fairly successful) results:

  1. Ortho Weed B Gon Max Plus Crabgrass Control.
  2. Spectracide Weed Stop for Lawns Plus Crabgrass Killer.

You can buy these herbicides in two different forms. One is the RTU form. RTU stands for "ready to use." This means that the product comes in its own spray bottle. The other form is the type that you have to screw onto your garden hose. The latter is a bit more work to use, but it is worth it if you need to cover wide areas. 

How to Use Post-Emergent Crabgrass Killers

Firstly, you will 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 is meant for your type of lawn. Otherwise, you could end up harming the good grass in your lawn.

In fact, the advice to follow label instructions carefully pertains to the whole process of applying a post-emergent crabgrass killer. But here is some advice that generally applies when using these products:

  1. As with pre-emergents, timing is critical. They work best on young, actively growing crabgrass plants. That usually means a portion of the June-July period.
  1. Prior to application, water the lawn (if the soil is dry) and mow (if your lawn grass is high).
  2. Apply only if no rain is in the forecast for the next 24 hours.
  3. Using a surfactant is often recommended. A surfactant is a substance that teams up with your herbicide to help it work better.
  4. Wait at least two days before mowing after applying.

A Healthy Lawn Still the Best Solution

Crabgrass is considered a grassy weed, as are some types of tall fescue. But there is another group of common lawn weeds as well. These are the broadleaf weeds. Different post-emergent herbicides exist for these two different weed classes (although Drive XLR8 also kills some broadleaf weeds). 

Want to avoid all of this hassle? Well, there is still some work involved, but, again, the best method to control crabgrass is to prevent it from coming up to begin with. Pre-emergent herbicides will help you achieve that. But on a more basic level, you need to keep lawn grass healthy enough to crowd out crabgrass by fertilizing it properly and removing large thatch buildups

Watering properly and providing good drainage are also essential. Even how you mow your lawn makes a difference. And at the first sign of thinning, overseed your lawn so that there will not be any openings where crabgrass can take hold.