How to Get Rid of Crabgrass, According to Lawn Care Experts
Bid those weeds adieu with these easy tips.
Yesim Sahin/Getty Images
Crabgrass, or Digitaria, is a headache for homeowners across the country. The weed, which is low to the ground and has many “legs” like a crab, is found in just about every type of turf and landscape—it doesn’t discriminate and will crop up anywhere, from athletic fields to golf courses, and most notoriously, in lawns.
The troublesome weed is the bane of a property owner’s existence because it spreads very quickly and is incredibly difficult to get under control—and once it takes over a lawn, it steals nutrients away from healthy grass. And because of its slightly shrubby appearance, it can harbor more pests. To tackle this pesky issue, we asked lawn care experts how to get rid of stubborn crabgrass—and keep it from coming back.
Related: Spring Will Be Here Before You Know It—Here's How You Can Set Your Lawn Up for Success
Meet Our Expert
Aaron J. Patton, Ph.D., Professor of Horticulture and Turfgrass Extension Specialist at Purdue University
Justin Stultz, Texas-based professional mower and lawn care expert at LawnStarter
How Crabgrass Grows
Crabgrass is a warm-season annual grass, which means that it thrives under dry, hot conditions. It germinates, lives, and dies in the same year, but the problem is that each bunch of crabgrass produces up to 150,000 seeds, which settle into the dirt and wait to germinate the following year, making it a vicious cycle. On top of this, seeds can actually hang out for at least 3 years in soil, so prevention is essential.
Identifying Crabgrass
According to Aaron J. Patton, Ph.D., professor of horticulture and turfgrass extension specialist at Purdue University, “There are many species of crabgrass, but the two most common species in lawns are smooth crabgrass (Digitaria ischaemum) and large or hairy crabgrass (Digitaria sanguinalis).”
He describes large crabgrass as having a hairy stem and leaves, while smooth crabgrass “will lack the hairs except for a few hairs at the collar region near the membranous ligule.” In general though, both are fairly similar in appearance and are opportunistic weeds that germinate almost anywhere.
Regardless of the type, you’ll be able to identify a crabgrass issue pretty quickly. Justin Stultz, Texas-based professional mower and lawn care expert from LawnStarter, says, ”It’s easy to spot crabgrass because it will usually ‘green up’ or grow quicker than other grass and has noticeably thicker, bright green-blue blades.” He adds that crabgrass branches out from a central location, giving it a clumpy or patchy appearance in your lawn. “A couple of days after a fresh mow, you will start to notice the crabgrass clumps growing back faster than the rest of your yard.”
How to Prevent Crabgrass
Prevention is essential when it comes to combating crabgrass, because once it settles in your lawn, you’re fighting an uphill battle. There are a combination of things you can do to stave off crabgrass, including maintaining a solid lawn care routine and using preventative products, like pre-emergent herbicides.
While you might be doing the best you can to keep crabgrass at bay, it’s possible your neighbors might not be doing their part. Stultz says, “Since crabgrass spreads by seeds germinating, it is likely to infest your yard from a neighbor’s yard or nearby fields that aren’t regularly treated with herbicides.” It might be worth coming up with a collective action plan that you and neighbors can enforce so crabgrass can’t invade your lawns.
Pre-Emergent Herbicide
Perhaps the most important thing to keep in mind is you’ll need to stop seed germination before it starts, which is when the weather starts getting a bit warmer, so you must treat your lawn with a pre-emergent herbicide when the temperatures hit around 50 degrees Fahrenheit. The first week of March is typically suggested for most regions. If you need a visual cue, forsythia plants and lilac bushes are known to bloom prior to crabgrass germination, so if you see those coming up, you need to jump on it.
Dr. Patton says, “The way they [pre-emergent herbicides] work is that as soon as new seeds sprout, they come in contact with the product, die, and fail to emerge. Many of these products are combined with fertilizer, however, so early spring fertilization of turf should be minimized” He advises looking for combination products with mostly “slow-release” forms of nitrogen.
Dr. Patton also recommends using a split or sequential application strategy—rather than applying only one application of a preemergence herbicide in the spring, apply a three-quarter or half-rate at the normal early spring application timing and apply a second application at a half-rate in late May or early June. As for the type of pre-emergent herbicide you should use, the below active ingredients are known to be effective at preventing seed-setting:
Benefin
Bensulide
Dithiopyr
Oryzalin
Oxadiazon
Pendimethalin
Prodiamine
Trifluralin
Tips
Nearly all pre-emergent herbicides will prevent traditional grass seed from germinating as well, so you’ll need to hold off on lawn overseeding until late summer or early fall.
Mowing
In addition to pre-emergent herbicides, Stultz says regular lawn maintenance, as well as a sufficient and regular watering schedule, will go a long way in preventing crabgrass (plus other weeds!) from taking over. So if you aim to just keep your turf dense and healthy, you’re already well on your way to success.
This all means mowing is hugely important here. Keeping your lawn too short increases the chances of germination and crabgrass establishment. Dr. Patton recommends keeping your grass 2.5 and 3 inches, depending on the type of turf you have. If you already have crabgrass-infested turf and don’t want to make it worse, thoroughly rinse the mower after use to remove seeds and avoid transferring them to uninfested sites.
Irrigation
This is an easy rule to follow: Just water deeply once a week. “Daily, light irrigations promote shallow rooting, non-drought hardy turf, and encourage crabgrass,” says Dr. Patton. He advises watering to wet the soil to the depth of rooting, and then do not water again until you see the first sign of drought stress (You’ll know it’s time when turf becomes bluish gray and footprints remain in the turf after it is walked on.)
Stultz adds, “I can’t stress enough the importance of a regular watering schedule for your yard. The general consensus, especially down South, is to water your yard early in the day (before 11 a.m.), and for longer periods of time in the summer.”
Fertilization
A healthy, green lawn can be achieved with the help of fertilizers—according to University of California’s Statewide Integrated Pest Management Program, they increase “turfgrass vigor and reduce the possibility of a crabgrass invasion.” Actively growing tuf will crowd out new seedlings because at that stage, they’re not very competitive.
Dr. Patton recommends applying 2 to 4 pounds of nitrogen per 1000 square feet each year to create a dense, lush lawn. He also advised appling 60 to 100% of the nitrogen in two applications during the fall: one in September and one in November after the final mowing. Skip doing this in the summer, “which may increase crabgrass vigor.”
Related: 4 Things to Do Now for a More Beautiful Lawn All Summer Long
Mulching
Mulching is another step you can take to prevent crabgrass, especially around shrub beds and trees—the mulch will block sunlight needed for germination and establishment. You can use wood chips or nuggets or composted waste. (Although note that crabgrass actually still germinates in the mulch! Move it around with a rake to reduce seedling establishment.)
Tips
Stultz says one extra thing you can do for prevention is to get a soil sample of your yard to “make sure it has the appropriate pH levels to discourage crabgrass growth and promote overall lawn health.”
How to Pull Out Crabgrass By Hand
Stultz says, “If you already have crabgrass, it’s not going away in one season. The best way to get rid of crabgrass is chemical treatments.” That being said, you could manually extract crabgrass for a short term solution, but Stultz cautions that without regular herbicide treatments, a regular mowing schedule (at a healthy grass height), and a consistent watering routine, it will be a reoccurring problem.
Technically, crabgrass doesn’t have super deep roots, but you should use a claw or trowel to fully extract the plant, not just your hands. And do not throw out your weeds in the compost—they could sprout there! Check your local laws first, but tossing them in the trash is ideal.
Chemical Herbicides for Crabgrass
While there are many “post-emergence” herbicides on the market, many are only effective against small, mild cases of crabgrass infestations. Severe cases should be handled by pros. Dr. Patton also says, “Do not attempt to control crabgrass with herbicides after mid-July because crabgrass plants are usually too large to control effectively.” He suggests at this point, it’s better to “tolerate the crabgrass until it dies with the first frost.”
In addition to these pointers, Dr. Patton warns that these products are actually more difficult to use than pre-emergence herbicides, so it’s imperative you follow label directions. and it is extremely important to follow label instructions. In terms of active ingredients, according to him, “Quinclorac is safest for turfgrass seedlings.” Another ingredient is dithiopyr, which is also used in pre-emergent herbicides, but anything with this chemical compound is typically only applied by pros.
Don’t apply herbicides on a rainy day, as the rainfall may wash away the product too quickly.
Stultz adds, “If you, understandably, aren’t a fan of chemicals, your local nursery or neighborhood big box store will have plenty of organic options to choose from. Just temper your expectations for speed of results when going the organic treatment route.”
Related: The 7 Best Weed Killers of 2023
Natural and Organic Remedies for Crabgrass
If you really want to go the all-natural, chemical-free route, you can, but there’s a good chance you won’t find success—at least not long-term success. Unfortunately, crabgrass is quite stubborn and requires heavy-duty stuff. Below are a few suggestions you can try for very, very minor cases of crabgrass. (Just don’t hold your breath!)
Boiling Water
The simplest, easiest trick we’ve seen is pouring boiling water over single, isolated patches of crabgrass to really kill it. You might need to do this multiple times to truly destroy the crabgrass.
Vinegar
Douse the weed with vinegar. If you do this several times, the plant shouldn’t be able to withstand the acidity and theoretically, it’ll destroy it down to the root.
Citric Acid
You can also purchase citric acid powder online (or use lemon juice) combined with vinegar to drench the plant.
Corn Meal Gluten
For a natural pre-emergent herbicide, you can use corn meal gluten after you’ve dethatched your lawn in the early spring, but the University of Maryland Extension says research data shows mixed results in its effectiveness.
Related: Stop Believing These 9 Lawn Care Myths
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