Fertilizer granules provide a simple and easy carrier to distribute pre-emerge herbicides that must be applied to our lawns prior to weed seed germination if the herbicide is to be effective. However, there is a downside to using many of these weed and feed fertilizers in the spring for our Southern lawns.
Some of these fertilizer products containing pre-emerge herbicides only are formulated with high nitrogen content for cool season turf species that can utilize the nitrogen at this time of the year. These fertilizers put on our dormant warm season turf species lawns now will most likely feed existing winter weeds. And those weeds will compete for space when our lawns begin their flush of spring growth unless a post-emerge herbicide is also applied.
With too early high nitrogen fertilization, you may also be setting your lawn up for cold injury from a late season freeze. Therefore, my suggestion is if you use a weed and feed fertilizer as a carrier for your pre-emerge herbicide, try to find a fertilizer formulation that is low in nitrogen or one that the nitrogen source is in a slow release form. Most Southern lawns can wait until they have gone through spring transition and have been mowed at least twice before applying spring nitrogen fertilization.
Published February 13, 2012
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. firstname.lastname@example.org