Thatch is a layer of decomposing turf debris that can build up above the soil level. Some degree of thatch (1/2 inch or less) is beneficial to a lawn. But as thatch gets thicker, the roots zones of turfgrass suffer from depletion of nutrients and water absorbed by thatch. Excessive thatch may also harbor pests. We dethatch turf mechanically by using vertical tines to cut through the thatch and pull debris to the lawn surface where it can be raked away. We recommend dethatching once spring turf growth is active - usually in May.