Core aerating helps degrade thatch and also helps solve some of the causes of thatch. Some lawns have serious thatch problems while others do not. Thatch is a layer of living and dead organic matter that occurs between the green matter and the soil surface. The primary component of thatch is turfgrass stems and roots. It accumulates as these plant parts buildup faster than they breakdown.
Thatch problems are due to a combination of biological, cultural, and environmental factors.
Cultural practices can have a big impact on thatch. For example, heavy nitrogen fertilizer applications or overwatering frequently contribute to thatch, because they cause the lawn to grow excessively fast. Avoid overfertilizing and overwatering. Despite popular belief, short clippings dropped on the lawn after mowing are not the cause of thatch buildup. In northern Illinois, environmental factors typically are another primary case of thatch.