The Best Crabgrass Killers for Weed-Free Lawns

Crabgrass can become a major problem in lawns and gardens without taking quick control. Try these effective products to get rid of crabgrass in your lawn.

BobVila.com and its partners may earn a commission if you purchase a product through one of our links.

The Best Crabgrass Killer Option

Photo: amazon.com

Crabgrass is an annual weed that frustrates homeowners year after year. It gets its name from how it grows—low to the ground with stems that radiate out from the center of the grass clump, resembling crab legs. When it comes to battling crabgrass in the lawn, the odds are stacked in the weed’s favor:

  • It germinates when soil temperatures reach between 55 and 65 degrees Fahrenheit, the average temperature during the spring and fall seasons in most areas.
  • Ungerminated seeds live in the soil for up to 30 years before sprouting.
  • A single crabgrass plant can produce 150,000 seeds during the growing season.
  • The weed can grow vigorously in hot, dry conditions.
  • It favors the thin and bare spots in your lawn.

Although crabgrass is an annoying weed that can take over a lawn in no time, you can eradicate it with a bit of planning. The best crabgrass killer for your lawn will depend on when you apply the product and how bad your crabgrass infestation gets. Read on for our guide to navigating the available options and our top recommendations for the best crabgrass killers.

  1. BEST OVERALL:Scotts Halts Crabgrass and Grassy Weed Preventer
  2. BEST FOR CENTIPEDE GRASS: Southern Ag 006130 Atrazine St. Augustine Weed Killer
  3. BEST FOR ZOYSIA GRASS: Ortho Weed Be Gon Plus Crabgrass Control Concentrate
  4. FOR USE IN FLOWER BEDS: Preen Garden Weed Preventer
The Best Crabgrass Killer Option

Photo: amazon.com

Types of Crabgrass Killers

There are two types of crabgrass killer. The preventive type keeps seeds from germinating and the other type kills mature plants. The best overall product will take care of crabgrass and other weeds that are choking out your lawn. However, it also depends on the time of year that you plan to tackle the weed.

Pre-emergent Herbicides

Pre-emergent herbicides, or weed preventers, stop weed seeds from germinating. When properly applied, they do the job of controlling annual weeds—those that grow from seed each year and then die at the end of the growing season. Pre-emergents do not kill existing weeds.

The timing of the pre-emergent application is very important. Homeowners must apply the herbicide when the weed seed is just about ready to germinate. If the herbicide goes on too early, before the soil temperature warms up enough, the pre-emergent will dissipate before it can complete the job. Applying pre-emergents after a seed germinates will fail at controlling the target weed.

In areas with long growing seasons, crabgrass can germinate for a long season as well. Pre-emergent herbicides have a defined effectiveness period, so it might become necessary to apply pre-emergent herbicides several times over the course of the season to keep the area weed-free.

Post-emergent Herbicides

Post-emergent herbicides kill weeds that are present (after they have emerged from the seed). They prove most effective for tough-to-kill weeds like crabgrass if applied when the weed is young and tender. Mature weeds might require multiple applications, which can also stress the lawn or other plants in the area.

For weedy lawns, the best strategy combines pre-emergent and post-emergent herbicides for a full attack. The pre-emergent halts germination that has not yet occurred while the post-emergent herbicide kills the existing weeds. Again, it might take multiple applications to kill weeds like crabgrass, depending on the time of year, weather conditions, weed maturity, and other site-specific conditions.

What to Consider When Buying a Crabgrass Killer

Selecting the best crabgrass killer for your lawn depends on several factors. Do you want a product to kill several types of weeds or target crabgrass specifically? Will you apply the herbicide in the growing season or during its dormant season? Homeowners should consider whether they want to kill crabgrass in an established lawn or a recently seeded one. A final part of the decision boils down to how many square feet you need to treat. Consider the options below before selecting the best crabgrass killer for your needs.

Selective vs. Nonselective

Herbicides come as either selective or nonselective formulas. Selective herbicides control specific weed categories, like “grassy weeds” or “broadleaf weeds.” The ingredients in these kinds of weed killers should be safe for nontarget plants like lawn grass while killing target plants like crabgrass or dandelions.

Always read labels on selective herbicides to be sure they will work for you. A product labeled as a “grassy weed killer” may or may not actually control crabgrass, and it may or may not be rated for use in the area you plan to apply it.

Nonselective herbicides kill all types of plants. These are useful in areas where you do not want plants, like mulched tree rings or driveway cracks. Nonselective weed killers also can help in preparing for a landscape renovation, like laying new sod or creating a new flower bed.

Application Method

Herbicides are available as either liquid sprays or dry granules. Granules are easy to apply evenly with a properly calibrated lawn spreader, and any leftover product simply stores in a cool, dry location until its next use. Pre-emergent or post-emergent weed-and-feed applications for lawns often come as granules.

Liquid sprays prove handy for broadcasting over large areas with a hose-end sprayer or spot treating small areas with a tank sprayer or trigger bottle. They sell as concentrated forms or ready-to-spray liquids. A ready-to-spray herbicide is convenient and minimizes the homeowner’s exposure to the chemical by eliminating the mixing requirement.

When spraying liquids, users must be cautious about wind speed and direction to avoid spray drift that can damage plants not in the target area. Plan a “route” to avoid walking through recently treated areas and then tracking the chemical elsewhere.

Warm vs. Cold Climate

Temperature controls the target weed and the effectiveness of the weed killer. Weeds are most susceptible to herbicides while they are actively growing. Crabgrass seeds germinate when the soil warms to about 55-degrees in the spring. In summer, the crabgrass plant matures and produces more seed until it dies when cold weather arrives.

A single spring application of pre-emergent might be sufficient to eliminate crabgrass in a cold climate location. In a warm climate area, using pre-emergent repeatedly throughout the growing season, if needed, along with spot treating with post-emergent herbicide effectively controls crabgrass.

Our Top Picks

With those key features and shopping tips in mind, we’ve narrowed the market to its top-rated products. One of these seven recommendations for the best crabgrass killer should suit your needs.

The Best Crabgrass Killer Option: Scotts Halts Crabgrass and Grassy Weed Preventer

Photo: amazon.com

1. BEST OVERALL: Scotts Halts Crabgrass and Grassy Weed Preventer

Prevention is the best cure when it comes to eradicating crabgrass. Scotts is a leading manufacturer of consumer lawn, garden, and pest control products. The company designed Halts Crabgrass and Grassy Weed Preventer to block weed seeds from germinating in the spring and fall. They also made it safe for all types of established lawns.

Applying this herbicide in early spring when the lawn is dry can prevent germination of crabgrass and other common lawn weeds before they start to spread. Applying Halts again in the fall prevents the germination of winter weeds such as annual bluegrass (Poa annua) and chickweed. As long as the pre-emergent goes on when the lawn is dry, then rain, snow, or freezing weather will not affect performance after application. Like any pre-emergent, Halts will not kill mature crabgrass but will prevent crabgrass seed from germinating.

The Best Crabgrass Killer Option: SOUTHERN AG ATRAZINE St. Augustine Weed Killer

Photo: amazon.com

2. BEST FOR CENTIPEDE GRASS: Southern Ag Atrazine St. Augustine Weed Killer

Southern Ag has produced a large variety of insecticides, herbicides, fungicides, plant growth regulators, safety equipment, and more since 1930. Warm-season grasses, such as centipede and St. Augustine grasses, are normally sensitive to herbicides. Not many large manufacturers have products that are safe to use on these delicate Southern grasses, but Southern Ag uses the active ingredient atrazine, which is safe to use on both centipede and St. Augustine lawns.

Southern Ag weed killer goes on the grass during both dormant and growing seasons. The best results come from applying it in early spring or dormant periods when weeds are small or have not emerged. The manufacturer recommends limiting applications to two treatments per year.

The Best Crabgrass Killer Option: Ortho Weed Be Gon Plus Crabgrass Control Concentrate

Photo: amazon.com

3. BEST FOR ZOYSIA GRASS: Ortho Weed Be Gon Plus Crabgrass Concentrate

Finding the best post-emergent herbicide that kills crabgrass without hurting the existing lawn can be tricky, especially for sensitive zoysia grass. Ortho makes it easy with Weed Be Gon Plus Crabgrass Concentrate. The product is safe to use on zoysia grass and is a good value. Weed Be Gon targets broadleaf weeds and grassy weeds, and works well on any warm-season grass that needs a lot of weed control.

For a large infestation of crabgrass, it’s best to wait until the spring or fall and use a pre-emergent herbicide. Ortho Weed Be Gon works best when weeds are small and actively growing and when applied to a dry lawn. For best results, homeowners should use a tank sprayer or hose-end sprayer attachment.

The Best Crabgrass Killer Option: Preen Garden Weed Preventer

Photo: amazon.com

4. FOR USE IN FLOWER BEDS: Preen Garden Weed Preventer

Imagine having a weed-free flower bed. Pre-emergents will take care of crabgrass in garden beds, along with other annoying weeds. Preen is the go-to brand for weed preventives that are safe for use around more than 200 established flowers, vegetables, trees, and shrubs. Preen Garden Weed Preventer works best when applied in spring after spreading mulch on flower and shrub beds and before weeds start growing.

If a gardener forgets to apply the preventive before the crabgrass and weeds pop up, adding it later works, with a few required steps before applying. The first step is to remove existing weeds, followed by mulching the area, applying the Preen product, and then watering it in to activate. The herbicide will block common broadleaf garden weeds such as chickweed, knotweed, purslane, and thistle, as well as grassy garden weeds like crabgrass, foxtail, and bluegrass, for up to three months.

FAQs About Your New Crabgrass Killer

When it comes to using pre-emergent and post-emergent crabgrass killers, timing is everything. Be sure to read the product’s label thoroughly and follow the manufacturer’s directions for the best results. Here are some common questions that arise when using a crabgrass killer:

Q. When is the best time to apply crabgrass pre-emergent?

Apply crabgrass pre-emergent when the soil temperature is around 50-degrees. Killing the weed might require a second application in areas with long growing seasons. Follow the manufacturer’s directions for timing.

Q. Will heavy rain wash away pre-emergent?

No. Rain activates pre-emergent by carrying it into the soil. However, digging and pulling existing weeds after applying the pre-emergent can reduce the product’s effectiveness.

Q. How do you apply a crabgrass killer?

Apply post-emergent crabgrass killer in the morning, on a dry day. Treat only the affected areas of the lawn. Coat the crabgrass evenly.