Crabgrass Management Plan Components

Crabgrass management is frequently part of discussions involving spring lawn care practices. Always take an integrated approach to crabgrass management in lawns, focusing on sound cultural practices for optimum results, rather than just relying on preemergence herbicides.

Last season was a banner year for crabgrass across Wisconsin. Many lawns came out of winter in poor condition, then warm, moist weather in early summer set the stage for an ideal growing environment for crabgrass. Affected lawns saw an explosion of crabgrass plants over the remainder of the summer. Unfortunately, high populations of crabgrass translates to production of an enormous amount of seeds for more crabgrass in the future.

Fortunately, crabgrass is an annual, so all those plants died at the end of last season and can only reappear via germinating seeds this season. Crabgrass is a warm-season grass, so seeds will not start germinating until soil temperatures warm into the 55 to low 60 degree Fahrenheit range and stay there for several consecutive days. Crabgrass seeds need light to germinate. This is why crabgrass flourishes in full-sun lawns that are thinner, allowing light to reach the soil.

Maintaining thick grass stands via cultural practices are key in preventing serious crabgrass problems each season. First on the list of cultural management tools is mowing height. Raising mowing heights to the three-inch range for the entire season will significantly lower the chances of crabgrass invasions. Adequate nitrogen fertilization is also a key component. Most full-sun lawns, where crabgrass prefers to grow, should at minimum receive both late spring and early fall nitrogen fertilization. Using controlled release nitrogen fertilizers is highly recommended. Ideal timing for spring fertilization is approximately the second mowing of the season.

Smaller amounts of water frequently applied to lawns in summer are ideal for crabgrass. Avoid this by watering thoroughly to the depth of the root system of lawns as conditions dictate. Mowing higher helps lawns deal with drought. Also avoid any lawn work that will create openings in lawns and soils during peak crabgrass germination times of summer; instead, hold off until late August.

Finally, lawns with previous serious crabgrass problems may benefit from a preemergence herbicide application this season. If your lawn has never had a crabgrass issue, there is no need to start using them now. Read, understand, and follow all product label directions thoroughly. Soils need to warm up, so there is no immediate rush to apply them. Forsythia shrubs dropping petals after full bloom is often used as an indicator for proper timing of preemergence herbicide application.            

For much more information, see our new crabgrass management article.