Crabgrass is a recurring problem in many home lawns, but it need not be. Crabgrass is a warm-season annual grass. Our lawns are composed of cool-season perennial grasses. Providing the right environment for desirable grasses to flourish deprives crabgrass of its best environment.
To keep lawns thick and healthy so there’s little space for crabgrass seed to sprout, you should:
Mow frequently, removing only 1/3 of the blade length each time.
Set the mower high: 2½” to 3″ during the hottest part of the summer.
Water consistently and thoroughly throughout the growing season, if possible. Apply enough water to bring the weekly total to one to one and a half inches of rain and irrigation water combined.
Fertilize more heavily in fall than spring.
Aerate the lawn in early fall as soon as temperatures cool, if soil is compacted or clay-like.
When crabgrass is thick and unsightly in late summer, use a de-thatching rake or a power rake to remove most of it. This prepares the ground for overseeding which can take place between mid-August and mid-September in Minnesota.