Broadleaf weeds are best controlled with a weed and feed fertilizer product or a post emergent broadleaf herbicide, which works only on actively growing plants. The herbicide needs to be absorbed by the plant for the control to be effective. Although applications in the spring and fall are both successful, spring is the preferred time to use a weed and feed because young seedlings, which are actively growing, are much easier to eradicate than mature plants. Also, eradication of broadleaf seeds is best before they have a chance to produce and disperse their own seed.
Daytime temperatures also should be at least 60 degrees. Avoid using any herbicides during the heat (> 85 degrees) of the summer as they can damage the desirable grasses.