When Do I Apply Broadleaf Weed Herbicide?

Clover is a common broadleaf weed found in lawns.

Broadleaf weeds, such as clover and dandelions, make a lawn look unkempt and could hurt or kill the grass. Applying broadleaf herbicides at the right time can make the difference between successful weed control and a failed attempt.

Timing

Most broadleaf herbicides will only kill the weeds and will not kill the seeds. Seeds will still spread and grow, so you will have to make more than one application every year. The Ohio State University recommends April through June in the spring and September through October in the fall as the best times to apply weed-killing herbicides.

Temperature

To maximize weed control, apply broadleaf herbicides when temperatures range between 65 and 85 F. If the forecast predicts that temperatures over the next 24 hours will drop below or rise above this range, do not apply herbicides.

Conditions

According to the Iowa State University, for best results do not mow the lawn before application and allow two to three days to pass before mowing. To prevent drift, do not apply herbicides on windy days. Do not apply if the forecast calls for rain in the 24 hours after application.

References

• Ohio State University Extension: Broadleaf Weed Control For Home Lawns
• Plant Talk Colorado: Controlling Broadleaf Weeds in Lawns
• Iowa State University Extension: Horticulture and Home Pest News -- "Control of Broadleaf Weeds in the Lawn"