Thatch is a tightly intermingled layer of living, decaying and dead roots and other plant parts, which develops on the soil surface.
Accumulation occurs when the rate of thatch production exceeds the rate of decay. If this accumulation becomes excessive, the overall quality of the lawn suffers and it is easily damaged by stress conditions such as drought (when the grass plant roots in the thatch rather than the soil).
Thatch build-up interferes with the performance of fertilisers, pesticides and irrigation. Excessive thatch increases the lawn’s susceptibility to insect and disease problems.
Balanced lawn care programmes that do not rely on excessive amounts of high salt fertilisers help to prevent the accumulation of thatch, as does the careful and conservative use of chemicals, which may sometimes be needed to address pest and disease problems.
Curing an existing thatch problem involves using machinery to remove the thatch via scarification or hollow-tine aeration, possibly in conjunction with the application of thatch digesting fungi to the lawn and soil amendments to reduce soil acidity and improve soil structure.