Mulching is really nature's idea. Nature produces large quantities of mulch all the time with fallen leaves, needles, twigs, pieces of bark, spent flower blossoms, fallen fruit and other organic material. Mulches reduce the growth of weeds, when the mulch material itself is weed-free and applied deeply enough to prevent weed germination or to smother existing weeds. Mulches keep the soil cooler in the summer and warmer in the winter, thus maintaining a more even soil temperature. Mulches prevent soil splashing, which not only stops erosion but keeps soil-borne diseases from splashing up onto the plants.
Organic mulches can improve the soil structure.
As the mulch decays, the material becomes topsoil. Decaying mulch also adds nutrients to the soil. Mulches prevent crusting of the soil surface, thus improving the absorption and movement of water into the soil. Mulches prevent the trunks of trees and shrubs from damage by lawn equipment. Mulches help prevent soil compaction.