In lawn care, thatch is a layer of organic matter that accumulates on a lawn around the base of the grass plants. Thatch is a combination of living and dead plant matter including crowns, stolons, rhizomes, and roots.

Turf cross-section showing thatch layer

Grass clippings do not generally contribute to thatch buildup as they can be easily broken down by soil microorganisms. Thatch is composed of about 25% lignin, a complex organic polymer that is highly resistant to decomposition. Thatch buildup can be caused by several factors:

  • Certain grass species are especially prone to thatch production
  • Acidic soils may not be able to support sufficient populations of decomposing microorganisms
  • Certain fungicides can stimulate excessive root and rhizome growth
  • Application of insecticides may reduce earthworm activity, leading to decreased bioturbation
  • Over-application of nitrogen fertilizers can stimulate excess growth as well as contribute to soil acidity

A small amount of thatch may provide a beneficial insulating effect against fluctuations in temperature and moisture. However, excessive thatch can cause root problems and lawn mower difficulties. A dethatcher may be used to remove thatch from a lawn.

See also

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  • Plant litter – Dead plant material that has fallen to the ground

References

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  • Landschoot, Peter (January 9, 2023). Managing Thatch in Lawns (Report). Penn State College of Agricultural Sciences. p. 1. Retrieved January 30, 2024.
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