Mulch saves water and weeding A mulch is simply a covering for the soil. Gardeners have used almost any material as a mulch, including old newspaper, foot-deep straw, grass clippings, tree leaves, roofing paper, and plastic. These and many other materials will work if they satisfy these two basic conditions: The mulch should help to retain water in the soil on hot days, and it should smother weeds. A third but less important...