Every lawn has a layer of thatch between the soil surface and the green grass.
Although it contains some living grass parts, thatch primarily consists of
accumulated dead grass stems and roots that resist decomposition.
According to findings of the Lawn and Landscape Institute at TruGreen,
a thin layer (one-half inch or less) is desirable, as it helps insulate your
grass against extreme heat and cold. Its cushioning effect also helps your lawn
stand up to traffic. But when thatch builds up beyond one-half inch, it
predisposes your lawn to problems and limits the benefits of lawn treatments.
Additional Information
Thatch
Thatch & Core Aeration
Adding to Drought Damage
Red Thread/ Pink Patch
Seed & Sod