Lawn and Landscape Checklist - April Apply a GreenView Lawn Food or spring fertilizer. If warranted, choose a lawn food that also contains crabgrass or broadleaf weed control. In general, the best time to apply crabgrass preventer is about the time the forsythia blooms start to drop in your area. Ensure your lawn mower blade is sharp and that the mower is cleaned after each use. Mow the lawn often enough that you are removing no more than one-third of the leaf blade. By mowing frequently, you can also leave the clippings and allow them to provide additional nutrients to the turf. If warranted, aerate your lawn. Avoid working in your lawn or garden if the soil is wet, as it causes compaction.