When is the best time to de-thatch a lawn?

The best time for your lawn to undergo renovation is just prior to or during the active growth phases of the growing season. De-thatching of cool season grasses may occur from the middle of March through May and mid-August through September. However, the fall months are the most productive time for de-thatching. Warm season grasses should be de-thatched during the late spring. Fertilization should occur after the de-thatching process.