If You Leave Grass Clippings on Your Lawn, You’ll Get Thatch
The widespread, but totally erroneous, belief that grass clippings left on the lawn creates thatch was debunked in the late 60’s by a study at the University of Rhode Island. They found that thatch is primarily composed of stolons, stems, roots, and rhizomes. Grass clippings, on the other hand, are mostly water and will break down quickly, returning nutrients to your lawn. So, feel free to mulch those clippings right back into the yard without worry.