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.

Crabgrass, viewed from the top Illustration: Common Weeds of the United States

These chemicals should be watered into the ground two weeks before you expect crabgrass seeds to sprout. The best time is usually late April or early May. (Typically, crabgrass sprouts around Memorial Day in the Twin Cities area.)

For serious crabgrass problems, apply pre-emergent herbicide a couple of weeks earlier to "hot spots" along curbs, sidewalks, and driveways, and sunny, south-facing, slopes. Do the rest of the yard in early May. Then repeat the application again the second or third week of June.

Pre-emergent chemicals have names such as Balan, Benefin, Team, Dacthal, Tupersan, and others. Only Tupersan (also called siduron) can be used if you are planting grass seed at the same time. All others will stop Kentucky bluegrass from sprouting. Read and follow label directions carefully.

H506C
Reviewed 12/98