Crabgrass is one of those grasses that grow in tough conditions. This makes it a bad weed for homeowners who want to grow thick, lush and green lawns. All the methods that we’ll apply to kill crabgrass will take into account that this weed flourishes in both warm and cool weather conditions.
The best way to kill crabgrass in your lawn is to apply a selective post-emergent crabgrass killer. It will remove the weed without killing lawn grass. Other safe crabgrasss control methods include using natural killers such as baking soda and vinegar, and growing a thick lawn to choke out the weed.
Timing to Get Rid of Crabgrass for Good
Crabgrass is a grass just like other grasses in your lawn. Applying combination herbicides won’t get rid of it. Of importance to note is that timing is important if you want to get rid of this weed permanently.
There’s a big difference between controlling perennial grass weeds and annual grasses. Annual and bi-annual grass weeds have a period of dormancy while crabgrass thrives all year round. That is why it is a perennial weed.
Crabgrass will thrive even in winter (November -- April) when most lawn grasses are dormant. Here are two timing tips that will help you get rid of crabgrass in your lawn:
- For spring, just before germination of this weed, apply a pre-emergent herbicide. This will prevent the seeds from germinating in your lawn.
- In the summer, use a potent crabgrass post-emergent herbicide to kill already existing weeds in your lawn.
As you can see, understanding the life-cycle of this lawn weed is key to eliminating it for good. Here’s a summary of what you need to keep on your calendar to control this weed.
|Spring||Soil temperature = 55 -- 60 degrees Fahrenheit. Crabgrass seeds germinate||Apply a pre-emergent herbicide for crabgrass control.|
|Mid-summer -- Fall||Warm weather; crabgrass is flowering and producing seeds.||Apply a good post-emergent herbicide, or uproot.|
|Winter||Cold temperatures, dormant crabgrass seeds.||Prepare to apply a pre-emergent.|
How to Kill of Crabgrass in Lawn
The best, natural way to get rid of crabgrass and perennial weed grasses is to dig them out rather than spraying them with Roundup or other herbicide of your choice. But that’s not the only way. Below, I’ve detailed different ways to eliminate this weed using organic methods as well as chemical methods.
1. Pull out the crabgrass
Even if you use a herbicide to kill crabgrass weed, you’ll still have to dig it out to completely get rid of it. But using a chemical is not really one of my favorite methods because it has detrimental effects on the surrounding lawn grasses.
I prefer removing crabgrass naturally, which involves digging it up. It is a great way of eliminating the weeds without killing lawn grass. Here’s a simple way to pull out this weed:
- Water the spots with crabgrass for about 30 minutes to soften the soil.
- Use a claw weeder or a pitchfork to uproot crabgrass. You can also use your hand if there just a handful of spots infested.
- Add rooting fertilizer or organic manure to the area.
- Reseed the bare spot in your lawn with good grass seed to regrow grass.
- Care for the new grass as usual.
Early in the spring, the shoots of crabgrass are still small. You can pull them out of your lawn and manage to get rid of them successfully unlike in the summer when the weeds are extensively grown.
Crabgrass has a crab-like root system. While it’s easier to uproot, you may want to use a claw weeder to make your work a lot easier. It uproots invasive weeds including crabgrass, dallisgrass, dandelions etc.
My favorite claw weeder is the Fiskars 39″ 4-Claw Weeder. (Click the link to see a video of how it works on Amazon).
Digging and uprooting can also cause a little damage to your lawn, so be careful not to end up with a sodding job to do especially if there are extended areas invaded with crabgrass.
2. Sponging with Roundup
Sponging or spot-treating is a great chemical technique for killing crabgrass and other perennial grasses in your lawn. It is different from spraying because you don’t want to affect the good grasses in your lawn.
Here’s how to kill crabgrass by sponging or spot-treating:
- Mow around the crabgrass for about 2 weeks to allow the weed to grow taller than your lawn.
- Put some amount of Roundup herbicide in a bucket and mix with a surfactant or sticking agent.
- Dip a sponge in the Roundup and lace the top part of crabgrass (2-3 inches of the grass blades).
- Repeat this process 2 to 3 times over the course of two weeks to allow the herbicide to kill the entire weed.
With sponging, the glyphosate in Roundup goes underneath and travels all the way down the grass weed, killing it to the root. Glyphosate is a non-selective herbicide that can easily kill perennial weeds as well as your lawn grass.
To get rid of crabgrass without killing lawn grasses such as Bermuda grass or St. Augustine, ensure that you don’t apply too much Roundup.
If you do, you’ll end up with a ring of death around the area you applied the chemical.
3. Apply a crabgrass killer herbicide
Use a product with Quinclorac. Simply spot spray the areas with crabgrass. You should, however, know that crabgrass should be treated in the spring with a pre-emergent. It helps a lot to stop the germination of weeds.
If you find some small breakouts of crabgrass, then treat it with an over the counter herbicide. The most effective herbicides are those containing quinclorac as the main ingredient. I prefer Primesource Quinclorac Liquid Crabgrass Killer because it works fast and effectively.
An alternative you can try is a herbicide with mesotrione as an active ingredient. A good example is Tenacity Turf Herbicide.
4. Use baking soda
Baking soda is a phytotoxin and will damage almost any plant leaves it comes in contact with. The phytotoxic effects are presumably due to the sodium content.
Even at % concentration, baking soda can start to kill crabgrass in your lawn. Making a solution out of it may not produce great results on lawn weeds, so the preferred method is to use its powder.
Here’s how to get rid of crabgrass by applying baking soda on it.
- Spray a little water on the crabgrass and other weeds in your lawn.
- Sprinkle baking soda powder on the weed.
- Allow a few days for it to destroy the weeds.
- Uproot the dead weeds and replant grass to fill in the spots
Caution: Baking soda will kill any plant it will come adequately in contact with. Fescues, Bermuda grass, St. Augustine or even Kentucky Bluegrass lawns will get damaged if you apply baking soda on their leaves.
I would recommend using baking soda on single patches of crabgrass rather than extended invasions. Check out my detailed guide on using baking soda as a weed killer and its side effects here.
5. Apply corn gluten
Corn gluten is one of the recommended organic crabgrass preventers. The best part is that it also works as a lawn fertilizer due to its high nitrogen content (10% by weight). It works by inhibiting crabgrass seeds from forming roots after germination.
According to the findings by the Iowa State University, corn gluten meal can be put down as a pre-emergent to prevent crabgrass and other weeds that germinate in spring.
However, the University of Maryland Extension notes that corn gluten does not prevent the germination of crabgrass. It only controls it by feeding lawn grass with sufficient nitrogen. In turn, the lawn grass ends up growing faster, choking out crabgrass.
6. Use vinegar to kill crabgrass
Vinegar is a natural solution that kills crabgrass and other weeds. To control crabgrass naturally, apply 20% vinegar on the weed. The organic solution will affect the cell membranes of the weed, causing rapid breakdown/desiccation of foliage tissue on contact.
Here’s how to use vinegar to kill crabgrass naturally:
- Add vinegar, salt, and dish soap in a plastic mixing cup
- Stir with a plastic spoon to mix the ingredients well.
- Pour a moderate amount of this vinegar solution on crabgrass.
- Repeat steps 2 and 3 above on all instances of weeds in your lawn.
This homemade solution can use household vinegar as an ingredient. It is much weaker than the commercial-grade organic vinegar weed killer. With a 20% concentration, simply pour the solution on the weed and let it die off naturally.
Note that you want to use herbicidal and not household vinegar. Herbicidal vinegar is an organic concentrate that acts as a non-selective herbicide for lawns. It can kill broadleaf and grassy weeds altogether.
Be careful not to apply it on your grass because it will kill any plant it comes in contact with.
Vinegar organic herbicide acts in the same way Roundup does. It will kill weeds (and any other plant it comes in contact with) to the root.
You can burn crabgrass to remove it from your yard using a heat gun, a blow torch, or a weed burner. This exposes the weed to extreme heat, which kills the cells in the leaves and the stems. The weed will not be able to manufacture food and it will die off instantly.
Remember, crabgrass does not spread through underground stolons. It is very easy, therefore, to control it by using a weed burner.
I would recommend this method for single instances of crabgrass in your lawn as opposed to widespread areas of weeds, especially if you’re using a normal blow torch.
Burning is a great way to kill grassy weeds without chemicals. Natural methods are the best and the ash goes right into the soil to feed it.
CAUTION: Do not attempt to burn crabgrass in a dry lawn. You risk grass fires that are dangerous because they spread really quick. Even in a green lawn, ensure you put safety measures in place, such as a standby garden hose with water in case a small fire starts.
Here’s a video on how to control crabgrass without chemicals using a weed burner.
How to Control Crabgrass (Prevention Options)
Timing is key when it comes to controlling and preventing crabgrass in your yard. From experience, if you wait too long, the weed will take root and you’ll find it hard to control it.
Here are 3 great ways of controlling crabgrass in your lawn:
Put down pre-emergent on time
What you want to do is control crabgrass early in the season, probably during the second mowing or so. During this time, you can use a crabgrass control product, usually called a pre-emergent or preventer. See my guide and tips on the best time to put down a crabgrass preventer.
I usually recommend choosing a crabgrass pre-emergent that contains fertilizer in it. One of my preferences for this is Vigoro Crabgrass Preventer and Lawn Fertilizer.
If you opt to try this product, ensure you choose one that contains time-release nitrogen in it to prevent burning out your precious lawn.
Overseeding Your Lawn
Overseeding is one of my favorite techniques for weed control and keeping my lawn lush green and thick. It is a simple technique of planting grass seed directly into the existing turf without having to go through the normal preparation procedures.
The result of an overseeded lawn is a thick, dense lawn and filled-up bare spots. But how does that control crabgrass weeds?
- The thick lawn grass chokes out any existing crabgrass, thus killing it naturally.
- An overseeded lawn prevents crabgrass from germinating, thus controlling it a lot more effectively.
You can overseed your lawn in either the fall or early spring, allowing the grass enough time to germinate and grow before the crabgrass starts growing in the summer.
Grow a thick, healthy lawn
Nothing beats a healthy, thick lawn. Even weeds struggle to germinate and outgrow a lawn that’s thick and dense. If there are any crabgrasses germinating in your lawn, you can choke them out easily especially early in the season with a thick lawn. But how do you make your lawn dense?
Here’s how to grow a thicker lawn and choke out crabgrass weeds:
- Water your lawn only once a week to promote a deeper, stronger root system. Watering more than once makes your lawn develop weaker roots, making it more vulnerable to tenacious grass weeds.
- Mow your lawn higher than you’re used to. It is recommended that you leave your lawn 2 -- 3 inches higher to crowd out crabgrass and prevent it from growing.
- Aerate and dethatch your lawn at least once a year. This is especially good for turfs with clay soil in them. Lawn aeration will help improve oxygen circulation and promote a healthier, thicker lawn.
- Fertilize your lawn enough especially if it is Bermuda grass. However, you want to use a time-release nitrogen fertilizer in order to control weed growth.
- Reseed or overseed in the fall to prevent crabgrass. But why in the fall? Fall is a season of warm days and cool nights. This will promote healthy growth of lawn grass especially when there’s dew in the morning.
Summer Crabgrass Control Tips
Winter Crabgrass Control Tips
Sources and References
University of Maryland Extension: Is Vinegar an Alternative to Glyphosate?