Weed and feed fertilizers have both fertilizer ingredients in them and herbicides targeted to broadleaf weeds. Most weed and feed fertilizers are pre-emergent, meaning they are used on weeds before the seeds germinate and begin growing. Spring applications are often recommended to stop seeds that overwintered from sprouting; as well as a fall application, as weed production ramps up in the cooler weather. In order for the weed and feed application to be successful, follow special watering and mowing considerations so the fertilizer and herbicides have time to work on your lawn.
Mow your lawn two days before applying the weed and feed product. Avoid mowing right before the application as this may burn the grass and the herbicide works better when grass isn't compacted from mowing.
Water the lawn the morning before application so that the weed and feed can stick to the ground and weed plants. Water just enough to wet down the lawn, not make it soggy.
Apply weed and feed at the recommended rate listed on the package, as this differs by brand and time of year. Avoid applying too much as this will damage your lawn.
Avoid watering for at least two days after the weed and feed application to prevent washing it away before it has a chance to work. Avoid mowing for one week, otherwise the weed and feed will be collected in the grass bag of the lawn mower, where it does no good.