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How to Get Rid of Crabgrass: Dealing with Crabgrass 101

February 19, 2024 | Categories: ,

A particularly nasty weed masquerading as a grass, crabgrass loves to pop up uninvited on turf across America. It’s always important to know your enemy, so we’ll cover what crabgrass is before we dive into how to control it in cool- and warm-season grasses.

Understanding Crabgrass

Crabgrass is an annual weed that falls under the Digitaria genus of grasses. It germinates in late spring and early summer and will attempt to grow—competing with and killing turf in the process. While technically a grass, it grows as an individual plant like other weeds. Crabgrass plants can grow up to a foot wide, and when they bite the dust in the fall, they leave a dead space behind, which is where they will attempt to come back next spring.

Crabgrass Profile

Type of weed: Annual

Germination period: Begins when soil temperature at two inches falls between 60 and 70°F for one and a half to three days.

What does crabgrass look like? Clumpy and green, with crab-like “legs” (stems) extending from a central stem. Can be mistaken for tall fescue.

While it may seem like a good idea to just mow over them—especially since crabgrass can blend in with turfgrass when it’s low enough—each plant contains thousands of seeds, and can make up to 150,000 of them. Crabgrass seed will stick around and return next year in the form of new weeds, so if you want to get rid of crabgrass without it coming back, it’s time to explore the herbicides and cultural practices that will send it packing.

How to Get Rid of Crabgrass

The methodology is going to be based on whether you’re working with cool-season grasses or warm-season grasses. Product efficacy may also depend on the specific type(s) of turfgrass that’s been infested with crabgrass. For example, a product labeled as a crabgrass killer for bermudagrass may injure St. Augustinegrass, even though they are both warm-season grasses, so be sure to check the label.

Cultural Practices

Before we cover pre- and post-emergent herbicides, we’ll cover a few ways to naturally reduce the presence of crabgrass:

  • Choosing resilient turfgrass: Some types of turfgrass are better suited than others depending on geography, and in turn, offer better competition to crabgrass.
  • Proper mowing height: Crabgrass germination can be reduced when your turf is at its strongest, so ensure your mower height is adjusted properly.
  • Fertilizing at the right time: Outpace crabgrass growth with some new growth of your own. Crabgrass may like to invade turf, but it shies away from fights with other seedlings.

Crabgrass Control Methods for Cool-Season Grasses

On cool-season grasses like perennial ryegrass, Kentucky bluegrass, fine fescue, and turf-type tall fescue, we’ll cover pre-emergent and post-emergent crabgrass killer, when to apply them, and the active ingredients that will provide control of the crabgrass.

Pre-Emergent Herbicides

Crabgrass will begin to germinate when the top two inches of soil are between 60°F and 70°F, so you should apply pre-emergent herbicides when soil temperatures are between 50°F and 55°F for optimal results. For our purposes, pre-emergents will act as a crabgrass preventer, killing the seedlings right after they germinate. The crabgrass growth cycle has more stages that we’ll cover in our post-emergent section.

Some of the most commonly used and best pre-emergents for crabgrass include: 

Whether you choose a granular option or opt for a crabgrass spray, the four above options are effective and have great track records. Be sure to consult the Label and SDS for application rates and requirements.

Post-Emergent Herbicides

While pre-emergents are your first line of defense against crabgrass, when crabgrass has already emerged, it’s time for post-emergent herbicides.

Each product is effective up until a certain point in the growth cycle, which is denoted by the growth of tillers, which are shoots that grow from the crabgrass’ base. Keep in mind that the quicker you kill it, the better. The more it grows, the more applications will need to be made.

Image of a six-tiller crabgrass plant with lip balm for size comparison.
Image of a six-tiller crabgrass plant with lip balm for size comparison.

Some of the best post-emergent crabgrass killers include:

Also used as a pre-emergent, controls crabgrass up to the leaf stage.

Both have tolerance on warm- and cool-season grasses. Controls crabgrass up to one tiller or when it has four or more. Anything in between will require another product.

Also a pre-emergent option, controls crabgrass with two applications spaced two weeks apart from each other, and before the four-tiller stage.

Specially designed to kill crabgrass and goosegrass, controls crabgrass up to the five-tiller stage.

Crabgrass Control Methods for Warm-Season Grasses

On warm-season grasses like bermudagrass and zoysiagrass, many of the same products used on cool-season grasses will work. We’ll cover all the products designed for warm-season grasses.

Pre-Emergent Herbicides

We’ve established that crabgrass loves warm temperatures, so warm-season grasses are especially susceptible. Like cool-season grasses, timing is everything. These products offer pre-emergent control on warm-season grasses:

Post-Emergent Herbicides

In cases where crabgrass has already emerged, let’s talk about post-emergent herbicides. These herbicides are specifically formulated for tackling weeds in warm-season grasses:

Also used as a pre-emergent, controls crabgrass up to the leaf stage.

Controls crabgrass up to one tiller or when it has four or more. Anything in between will require another product.

May be used on zoysiagrass but not bermudagrass.

Choosing Herbicides for Crabgrass

Whether you need to restock on pre-emergent or you’re seeking advice, your ATS rep is here to help. If you want to learn more about preparing for, preventing, and getting rid of crabgrass, reach out.

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