Thatch in lawns is the accumulation of dead grass stalks, stems and roots. The right amount of thatch is beneficial to lawns, but once it exceeds an inch or so it can become a problem. When that happens some of the thatch needs to be removed. We choose to power rake in order to remove excess thatch. Power raking pulls thatch up to the surface where it's gathered and disposed. Usually we'll recommend that core aeration follow power raking. The holes left by aeration allow for air to circulate into the thatch speeding up the decay process and helping to keep thatch build-up under control.