- 1). Stay attuned to the weather forecasts and be sure to apply post-emergent herbicide on actively growing weeds and crabgrass. Target a period after a recent rain when there will be three or four successive days of dry weather. Apply on a sunny day when there is no wind and temperatures are expected to be between 60 and 90 degrees.
- 2). Pour one bag of post-emergent herbicide into a lawn spreader. Apply to your lawn in to-and-fro swaths in the same manner as when you mow. Check on the bag of herbicide for the appropriate setting for your brand of lawn spreader. Be watchful for any sign of your lawn turning brown during the application process. If this happens, it means you are applying too much herbicide and need to immediately soak your loan to dilute the herbicide.
- 3). Fertilize your lawn once a year to help establish a dense, healthy turf, which will help create a mat that is difficult for weed and crabgrass to break through. Be sure not to cut grass too short to create bald spots in your lawn, which are a prime spot for weeds and crabgrass to establish a toehold.