Thatch is a collection of dead plants parts like stems and grass clippings that accumulate on the soil surface. Thatch is not a problem unless it becomes thicker than.5 inches and grass roots begin to grow into it 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. If you mow and fertilize properly, your Kentucky Bluegrass lawns should not develop a thatch problem.
How to Dethatch:A good way to prevent any potential thatch problems is to give your lawn a good raking at least once a year. If your lawn is huge, don’t bother. If your lawn is manageable, pick a nice day in late winter and use a mental-tined leaf rake. Try to work the tines down the soil surface. Finally, collect and remove all debris.
Occasionally, a Kentucky Bluegrass lawn will accumulate greater than .5 inches of thatch during the growing season. This is usually a result of improper mowing or excessive fertilizing. Lawns like this will be weak and thin by end of summer. One way to handle such a problem is to rent a vertical mower, or “dethatcher,” from a tool rental store in early fall. Vertical mowing is a way to cultivate the top layer of soil and remove thatch. It should be used on a Kentucky bluegrass lawn if you plan to reseed immediately afterwards. Even then, be extremely careful. Vertical mowing is tricky and will damage the Kentucky Bluegrass plants that remain. Make only one pass across your lawn. Thoroughly rake and remove all the subsequent debris prior to reseeding.