Crabgrass can torment you for years once it invades your lawn. A few innocent-looking seedlings pop up here and there in spring. Then the crabgrass spreads all summer, smothering everything in its path. This warm-season annual easily overtakes thinned-out spots in the lawn, with each plant forming a mat that can produce up to 150,000 seeds. The crabgrass dies off at the first frost, leaving you with ugly brown patches and a massive seed bank.
The best way to end this cursed cycle is by stopping crabgrass before it starts. This is the time to apply a pre-emergent herbicide on your lawn to prevent crabgrass from germinating. Once crabgrass starts growing, it’s much harder to keep under control.
The Best Way To Control Crabgrass
The best way to control crabgrass is by preventing it from sprouting with a pre-emergent herbicide. Even if you can’t stop every weed from germinating, you won’t have nearly as many to tackle. Depending on the product you use, the pre-emergent may also control lawn weeds like dandelions.
Unfortunately, pre-emergent herbicides prevent grass seed from sprouting, too. If you want to overseed patchy areas in your lawn, you may have to wait and do it in the fall. This is something you should weigh before choosing a pre-emergent product, which we’ll cover below.
When To Apply Pre-emergent Herbicide To Prevent Crabgrass
Pre-emergent herbicide prevents weeds from germinating, but it won’t kill off crabgrass that has already sprouted. Crabgrass begins to germinate after the soil temperature remains at or above 55 degrees Fahrenheit for several days. The best time to apply pre-emergent herbicide is in late winter or early spring when the soil temperature is between 50 and 55 degrees. Apply the product too early, and it could break down before the crabgrass starts germinating. Apply it too late, and you’ll already have weeds.
Depending on how far south you live, the appropriate time to treat your lawn could be anywhere from mid-February to early April. Once the weather starts to warm, stick a soil or meat thermometer 2 inches into the ground to determine the temperature. Soil temperature can fluctuate early in the season, so you may want to check it for a few days. Time application for just before a rain, or you will need to water it in with your sprinkler.
Horticulturalists have another trick: Watch the forsythia. Apply pre-emergent herbicide before the forsythia bushes in your neighborhood start to shed their yellow flowers.
Types Of Pre-emergent Herbicides
Any of these pre-emergent herbicides can be effective at stopping crabgrass in your lawn:
Corn gluten meal: If you prefer an organic product, use corn gluten meal on your lawn. This natural byproduct won’t burn plants or harm pets or children. The nitrogen it contains even fertilizes your grass. However, corn gluten meal is only about 65 percent as effective as other pre-emergent chemicals. It will also fertilize any weeds already growing in your lawn. On the plus side, corn gluten meal breaks down in four to six weeks if you want to reseed this spring.
Chemical herbicides: Several pre-emergent herbicides are on the market. Check product labels carefully to see how long they last. If you already applied prodiamine in the fall, it can control weeds until summer (though some homeowners apply the herbicide at 50 percent strength and do one application in fall and another in spring). Dithiopyr usually lasts three to four months, while pendimethalin stops weeds for about six weeks.
Other Crabgrass Control Tips
Here are a few more tips to keep crabgrass under control this year:
Hand-pull crabgrass while it is young if you can. It’s easier to get rid of and won’t get a chance to spread seeds.
Keep your lawn thick and healthy. Mow cool-season lawns at 3 inches to help shade out crabgrass.
If the crabgrass is too widespread to hand-pull, use a post-emergent herbicide for lawns. Check the label to make sure it won’t harm your grass.
Remember that you don’t have to use weed killers if you lose the battle this summer. Unless you live in a frost-free climate, winter will kill off all of the existing crabgrass, and you can use pre-emergent herbicide next year.
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