Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow . It’s critical that you know what turf grass you have in your lawn. Cool season turf grasses begin active growth in fall and need fertilizer at that time. But warm season grasses are preparing for dormancy and should never be fertilized as fall approaches, not after August 15 give or take a week or so depending on your location. Although fall is an appropriate time to apply a pre-emergent herbicide for winter weeds,