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

FAQ
Question: 

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

Answer: 

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 generally less effective than fall applications. 

Effective broadleaf herbicides include 2,4-D, MCPP, MCPA, dicamba, triclopyr, and others.  The most effective broadleaf herbicide products contain a mixture of 2 or 3 herbicides as no single compound will control all broadleaf weeds.  Broadleaf herbicides can be applied as liquids or granules.  Before applying any herbicide, carefully read and follow label directions.