WSU Extension

Hortsense

Lawn and Turf : Thatch
(revision date: 6/22/2015)


Biology
Thatch is a layer of plant debris which generally accumulates at the soil surface. It consists primarily of undecomposed stem, crown, and root materials. Grass clippings contribute little to thatch formation. In healthy lawns, thatch decomposition rates balance grass growth, resulting in relatively little accumulation. However, excess fertilization, overwatering, and improper mowing will aid thatch accumulation. Also, acid soils may result in reduced thatch decomposition rates. Thatch in excess of 1/2" should be removed, as it can prevent water penetration. Crowns and roots can develop in the thatch rather than in the soil, making frequent watering necessary and making lawns more prone to drought injury. Certain types of grass naturally develop more thatch. Creeping bentgrasses produce large amounts of thatch, and are not recommended for home lawns.
Management Options

Non-Chemical Management
  • Provide adequate fertilization.
  • Deep, infrequent watering encourages deep root growth.
  • Soil aeration may be necessary to improve water penetration.
  • Remove thatch as necessary, preferably in early spring, using a power rake or by hand. Work in two directions (i.e. N-S, then E-W), removing 1/2 of the total desired amount in each direction. Reseed as needed.
  • Mow regularly at recommended height.
  • For more information on proper lawn care see EB0482E, Home Lawns.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

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Caption: Thatch
Photo by: R.S. Byther