Thatch is the layer that forms between the soil surface and the green grass. While it contains some living grass parts, the majority is an accumulation of dead grass stems and roots that are resistant to decomposition. Grass clippings from proper mowing decompse rapidly and contribute very little to thatch development.
A thin layer of thatch - 1/2" or less - helps insulate your grass against extreme heat or cold. It also has a cushioning effect that helps your lawn stand up to traffic. However, if the thatch builds up past 1/2", your lawn will be more vulnerable to problems and lawn care products will not be able to work as effectively. Sodded and fine fescue lawns have a tendency to get excessive thatch.
:: Thatch-Related Lawn Problems
Thatch affects plant growth in several ways. A thick thatch layer often harbors disease problems and makes control of some turf insects more difficult. Thatch retains water and prevents moisture from reaching the soil. Then, grass roots grow in the thatch rather than the soil below. This can result in a lawn that is more prone to drought stress and high or low temperature injury.
:: Remedies for Thatch
Core aeration is the best way to maintain thatch. The holes opened by aeration permit infiltration of water and air, stimulating thatch breakdown. The soil brought to the surface contains fungi and bacteria that further decompose thatch.
