Written by Master Gardener Bev Kindschy
Crabgrass is one of the most common weed problems in lawns. Its gets its name because the leaves form a crab-shaped design. Crabgrass seems to appear in close-mowed lawns and bare spots and in the fall it turns a brownish red color. Seed heads show up in the summer and fall and stems will continue to spread unless they are stopped. The best prevention is dense, healthy, thick turf, which prevents it from invading because crabgrass seeds need light to germinate.
However if you haven’t had that success with your lawn, you may need to go on the offensive by treating your lawn with a preemergent herbicide in the spring, to prevent the crabgrass from germinating and spreading You will want to do this in mid to late April when the ground temperature is about 52 degrees.
To check the ground temperature in this area, you can reference www.greencastonine.com. Click on Agronomic Tools, Soil Temperature Maps. You’ll see the date in the upper left corner. Click on Wisconsin, and zoom in to see the temperatures.
If you don’t get your preemergent down before the warm temperatures are here, you’ll need to wait until next spring. FYI…One crabgrass plant is capable of giving off 100,000 crabgrass seeds. All the more reason to get rid of this weed.