Here’s everything you need to know about how to spot the weed, wipe it out, and keep it from coming back next summer.
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Crabgrass infestation in home lawn
Credit: Getty Images

It will creep, it will crawl, and if you let it, crabgrass will demolish your summer dreams of a lush lawn faster than you can say, "Honey, grab the herbicide." If we haven't set your green thumb nervously thumping yet, Dr. John Kauffman, a regional technical manager for TruGreen says the weed's spread is the real cause for concern.

"Similar to a crab, this type of grass is fast-moving and able to crawl across your entire yard," he says. "If left untreated, crabgrass can aggressively overtake large patches of your lawn in the blink of an eye." It's certainly alarming to see these low, gangly weeds sprouting about your yard, but if you're armed with the right information, you should be able to eradicate it without much issue, especially if you catch it early.  

What Is Crabgrass?

Let's start with the basics. According to Kauffman, crabgrass is not a form of grass, contrary to what its name might imply. "Crabgrass is an annual warm-season weed, which means it thrives in the heat and will sprawl anywhere it can find sunlight, water, and bare soil," he says. You'll begin to see it sprouting up in yards across the South as early as February, once the soil temperature has stayed above 55 to 60 degrees Fahrenheit for over a week. "For Florida residents, keep in mind that crabgrass pretty much thrives all year long due to Florida's naturally hot climate," Kauffman warns.

What Does Crabgrass Look Like?

A representative for Sunday lawn care says that one of the trickiest aspects of crabgrass is just how biologically similar it is to turfgrass. Because it thrives in the toughest conditions, it's important to jump on a treatment plant immediately, but you'll need to know what to look out for first. "The most distinguishing characteristic of crabgrass is its stems, which typically grow out rather than up," says Kauffman. "This also sheds some light on the name, as the weed often resembles a gangly bunch of crab legs, sprawling out from the center." Kauffman shares other key indicators of crabgrass include patches of coarse, discolored-looking grass and leaves that are lighter in color and wider and broader than those of surrounding turf. 

Crabgrass Control

Once you've spotted crabgrass—whether a patch or a full-blown infestation—the time to act is now. "Without proper prevention techniques and regular maintenance, a crabgrass invasion can quickly spiral out of control," says Kauffman. The reason for the quick spread might have something to do with the fact that, according to Sunday, each plant produces over 150,000 seeds. Yikes. Kauffman warns that once the seeds that have spread throughout your soil begin to germinate, it's only a matter of time before it spreads out across your lawn, making it even more difficult to remove.

If possible, it's best to skip the invasive phase and just avoid the seeds getting to your lawn in the first place. "Crabgrass seeds are sneaky and can remain viable in the soil for up to three years," says Kauffman. To prevent this case altogether, he recommends pre-emergent herbicides but warns that the timing of the treatment has to be "just right" in order to have the proper effect.

Let's say you missed the window for the pre-emergent route and find yourself in a post-emergent crabgrass world, how long will it take before your lawn starts to resemble the lush carpet you once knew? According to Kauffman, that depends on the severity of the infestation. "Small infestations that are treated early can be controlled with one treatment and will begin to disappear in a week or so," he says. "Large infestations may take a couple of treatments and can take six to eight weeks for complete control." But after the wait, your work isn't over quite yet. The rep at Sunday warns not to let the bare soil sit once the crabgrass has been wiped out but, instead, patch it with sod or seeds right away. "A dense, thick lawn is always your best defense against weeds!"