How to Halt Crabgrass
Roger Cook details a plan for a crabgrass-free lawn
I first noticed crabgrass sprouting in my front lawn in July. By September, it had overrun the entire yard. What should I do so that this problem won’t occur next year?
—Stephen Robinson, Gainesville, VA
Complaints about crabgrass invading lawns always reach a crescendo in late summer and early fall. But the problem really starts much earlier, in the spring, when crabgrass seeds begin to germinate. Crabgrass is an annual—it dies in the winter and only grows from seeds—so the best way to stop it is with a pre-emergent herbicide, such as Halts Crabgrass and Grassy Weed Preventer (). Pre-emergents form a chemical barrier on top of the soil that temporarily inhibits a seed’s root growth without affecting established plants.
Timing the application is critical. Spread it too early, and it will lose effectiveness. Spread it too late, and the barrier won’t stop germination. I use forsythia as my signal to spread: As soon as its flower buds show, down goes the pre-emergent.
To ensure even coverage, I set the broadcast spreader at half the recommended application rate and go over each spot in the lawn with two passes at 90 degrees to each other. I don’t bother applying it in shady spots because crabgrass only grows where it’s sunny. Then, if no rain is forecast, I’ll thoroughly wet the stuff down.
That stops the evil weed in established lawns. But if you’re planting a new lawn in the spring, only use a crabgrass preventer with Tupersan (a.k.a. Siduron) on top of the new grass seed. Unlike other pre-emergents, Tupersan lets turf grass sprout, but not crabgrass. (To simplify things, all of Scotts’s crabgrass preventers contain it.) Just remember, its effectiveness depends on a reapplication four to six weeks later.
Shown: To stop a crabgrass invasion, Roger Cook applies a pre-emergent herbicide in the early spring using a broadcast spreader.