Dethatching
The thatch is the layer of living and decomposing stems, roots, and other lawn debris between the green blades of grass and soil surface. Some thatch can be benefical to your lawn because it helps to limit weed germination, reduce water evaporation and protect from frost damage. Accumulation of too much thatch can give insects places to hide and prevents water, air, and nutrients from penetrating the soil preventing proper root growth and overall lawn health.
Thatch build up can be reduced by detatching. Detatching should be performed mid to late spring or early fall when the grass is actively growing.