How To Get Rid Of Crabgrass That's Growing In Your Lawn And Prevent It From Coming Back

Chances are, if you have a lawn, you have crabgrass! This fast-growing weed thrives despite heat, humidity, or drought conditions. “It’s a prolific seed producer,” says Clint Waltz, PhD, turfgrass extension specialist at the University of Georgia. “If you do nothing about it this year, expect a higher and more dense population of crabgrass next year.”

Crabgrass first appears in the spring, but new plants keep germinating throughout the summer, says Waltz. As an annual weed, crabgrass is killed off by the first frost. But by then, you’ve got hundreds—and probably thousands—of seeds sitting there waiting to germinate next year. Even worse, the seeds can remain viable in the soil for years.

There are many different types of crabgrass (Digitaria spp), but getting rid of them requires the same approach, says Waltz. A pre-emergent product, which interferes with a weed seedling’s ability to mature, is best and is applied in the spring. But if you missed that time frame, you still can get rid of crabgrass once it shows up in your lawn in early to late summer.

How To Get Rid of Crabgrass

If you see crabgrass by mid to late summer in your lawn, you may not have applied a pre-emergent herbicide in the spring. However, you still can get control by following these steps:

• Dig up individual plants. This method is an option only if you have a few plants here and there.
• Identify your grass species before using herbicides. “Herbicides are grass specific, and if you use the wrong one on your lawn, you may harm it,” says Waltz. If you’re not sure what kind of grass you have, contact your local university coop extension service (find yours here).
• Choose the correct post-emergent herbicide product for your type of grass. These products must be purchased through a commercial landscape company or feed and seed store. You won’t typically find them at big box retailers. Look for the following active ingredients on the product labels, and use according to label instructions:
  -Sethoxydim can be used on centipede grass and fine and tall fescues
  -Fluazifop can be used on tall fescue and zoysia
  -Quinclorac can be used on Bermuda, tall fescue, zoysia, and Kentucky blue
• Spot spray the product on crabgrass plants. You should see results in about 7 to 10 days with the crabgrass turning yellow and brown. In some cases, you may need a second application after 21 days if you still have healthy-looking crabgrass, says Waltz.
• For widespread infestations, spray the entire lawn. If 50- to 70-percent of your lawn area is covered with crabgrass, you should spray the entire lawn according to label instructions for the most efficient approach, says Waltz.
• Mow your grass. Wait for a few days after herbicide application, then mow your lawn, which will make the discolored areas appear less noticeable.
• Time your application right. Start spot spraying any time you see crabgrass plants emerge. But if it’s late summer and close to the first expected frost date, don’t waste your time, money, and energy. Because it’s an annual weed, crabgrass will be killed by the first frost of the season anyhow.
• Don’t rely on DIY remedies. Using boiling water or horticultural vinegar aren’t effective long-term solutions, and “they’re non-selective so they can damage the desirable grass, too,” says Waltz. Home remedies also are not absorbed and translocated throughout the plant to kill the roots, so these methods may damage the foliage but don’t kill the roots.  

How To Prevent Crabgrass

The best way to prevent crabgrass or any other weeds from competing with your desired grass for light, water, and nutrients is to ensure your lawn is healthy and dense, says Waltz. That means mow your grass at the proper height for your species, and fertilize and irrigate correctly.

Also, if you had crabgrass this year, make sure to apply a pre-emergent product next spring. Get it down before crabgrass germinates, which is before the soil surface temperature reaches 55 degrees in early to mid-spring (find soil temperatures here).  

As for corn gluten, often sold as an organic pre-emergent product, it has 20- to 40-percent effectiveness. That means it’s not a reliable way to prevent crabgrass and other weeds from taking over your lawn, says Waltz.

Identifying Crabgrass

Crabgrass is one of the most common (and most hated!) weeds found in lawns. Crabgrass germinates when soil temperatures reach 55 degrees F for a few days. Depending on the temperatures in your area, you may see crabgrass as early as March in some years, says Waltz.

Crabgrass can form large clumps in areas of sparse turfgrass, and it also pops up in cracks between pavers, walks, and driveways. It’s coarse and pale green and has a low-growing form, with stems creeping across the ground and spreading out from the center of the plant to resemble a crab’s legs.

The seedheads have finger-like spikes that arise from different points at the top of the stem. While most crabgrass spreads by seed, some species root by creeping stems, or stolons, says Waltz.