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Tips for controlling crabgrass in your lawn

March 31, 2021

Now is the time to apply crabgrass preventer in the Twin Cities metro area

This spring is about 2.5 weeks ahead of normal based on daily temperatures and growing degree day accumulation. We just entered the window to apply crabgrass prevention products.

Now is the time to apply pre-emergent herbicides to lawns in the 7-county Twin Cities metro area. This optimum application window could end around April 10.

What is crabgrass?

Several large crabgrass plants, with seed heads, growing along a curb.
Large crabgrass

Crabgrass (Digitaria spp.) is considered a weed but having “grass” in its name can cause confusion for some. Though it is a type of grass, it is not considered an appropriate species for a lawn.

Crabgrass is an annual plant whereas turfgrass species used for lawns are considered perennial plants. This means a crabgrass plant will germinate in the spring, grow throughout the summer, and die as late fall or winter begins. A perennial plant that you might use in your lawn, such as fine fescue or Kentucky bluegrass, will go dormant in the winter and continue growing year after year.

Crabgrass can often be identified by the older leaves and sheathes turning a dark-reddish color. It thrives in areas of your lawn that are thinner or bare of vegetation.

A crabgrass plant can produce thousands of seeds every year meaning crabgrass control can potentially be very important to the overall health of your lawn.

Controlling crabgrass in the spring

An effective way to eliminate crabgrass is to apply a pre-emergent herbicide before the crabgrass seed in your lawn can germinate. Timing when you apply the pre-emergent herbicide is very important. If done too early, while it is still too cold, crabgrass will most likely grow anyway. If applied too late, you may not see much benefit either. You should consider applying a pre-emergent herbicide when soil temperatures in your area approach 55 degrees F.

Many resources exist to help determine when this occurs, such as the growing degree day (GDD) tracker from Michigan State University. This tracker can be helpful if you live in the Great Lakes region of the United States.

To use the tracker, enter your zip code and click the Crabgrass PRE tab along the right side of the map for temperatures in your area.

GDD tracker map from Michigan State University. Green areas show where crabgrass pre-emergent should be applied; orange areas show where it is too late to apply herbicide.

I missed putting down my pre-emergent, what can I do?

If you happen to miss the window for applying a pre-emergent herbicide you still have options. Post-emergent herbicides like quinclorac and mesotrione can be effective, but you need to apply them while plants are still young. The longer you wait, the less effective they will become.

Hand pulling crabgrass plants is also an option, but can be time-consuming and potentially labor-intensive.

One of the best strategies to combat crabgrass, and other weeds in general, is to maintain a healthy lawn. A thick, healthy lawn has a robust root system with lots of aboveground growth to outcompete many lawn weeds.

To learn more, please visit these other resources available from the University of Minnesota.

Authors: Shane Evans, lawn water conservation educator and Maggie Reiter, Extension turfgrass educator

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