Thatch is a collection of dead plant parts like stems and grass clippings that accumulate on the soil surface. Thatch is only a problem if it becomes thicker than .5 inches and grass roots begin to grow into the thatch as if it was soil. Thatch dries very quickly in hot summer conditions and grass roots growing in it are much more susceptible to drought once the thatch dries. Lucky, fescue lawns seldom accumulate thatch if mowed properly.
How to Dethatch:
A good way to prevent potential thatch problems is to give your lawn a good old-fashioned raking at least once a year. I like to do this n the late winter, using a metal-tined leaf rake. Try to work the tines down to the soil surface. Finally, collect and remove all the debris. Occasionally, a fescue lawn will accumulate more than .5 inches of thatch during the growing season. This is usually as a result of improper mowing or excessively fertilizing. Lawns like this will be weak and thin by the end of the summer.
One way to handle such a problem to is rent a vertical mower, or “dethatcher,” from a tool rental store in early fall. Vertical mowing is a way to cultivate the top later of soil and remove thatch. It should be used on a fescue lawn only if you plant to reseed immediately afterwards. Even then, be extremely careful. Vertical mowing is tricky and will damage the fescue plants that remain. Make only one pass across your lawn. Thoroughly rake and remove all the debris prior to reseeding.