Thatch is the layer of living and dead stems, roots, stolons, and rhizomes between the green blades of grass and the soil surface. A thin layer of thatch (less than 1/2 inch thick) can be beneficial to the lawn because it helps to limit weed germination, reduce water evaporation, and protect from frost damage. However, thick thatch layers can prevent water, air, and nutrients from penetrating the soil, causing reduced root growth and increased potential for drought stress. Thatch also favors fungal growth and can harbor insect pests.
Power raking also is a process of removing dead grass so the soil can breathe and the grass can grow more efficiently. Power raking is a more gentle process than dethatching and is designed to tear out only the grass material at the surface of the soil.