Yard and Garden: Timing and Applying Broadleaf Lawn Herbicides

AMES, Iowa – The air has a bit of a chill in it in the mornings. Fall is almost here, which means it’s time to think about preparing lawns with weed control. Fall is an excellent time to apply broadleaf herbicides for perennial broadleaf control, but take care to do it properly and effectively.
Iowa State University Extension and Outreach horticulturists can help answer questions about the right time and methods to apply broadleaf herbicides.To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

When is the best time to apply a broadleaf herbicide to the lawn?

Fall (mid-September to early November) is the best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides. In fall, perennial broadleaf weeds are transporting food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds. Spring applications are less effective than fall applications.

Which herbicides will effectively control broadleaf weeds in the lawn?

Effective broadleaf herbicides include 2,4-D, MCPP, dicamba, triclopyr and others. The most effective broadleaf herbicide products contain a mixture of two or three herbicides, as no single compound will control all broadleaf weeds.

What is the proper way to apply a broadleaf herbicide to the lawn?

Broadleaf herbicides can be applied as liquids or granules. Before applying any herbicide, carefully read and follow label directions. 

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About the Authors

Richard Jauron, Extension Horticulturist
Greg Wallace, Organizational Advancement
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