1609 Organic mulches Mulches are useful additions to landscapes for several reasons. Many plant wastes can be recycled as organic mulches that aid plant growth in several ways. Mulches reduce weed-growth around plants. Organic mulches, such as wood chips, must be three to four inches thick to effectively keep weeds down. Organic mulch eventually breaks down improving soil, which means you'll need to replace it after several years.
Mulches save water in the Garden because they reduce evaporation from the soil surface.
Inorganic mulches, such as rock, can also hold in moisture. Mulches also improve water penetration and minimize soil crusting. Some people prefer to use spun or woven landscape fabric under wood chips or gravel. Unlike solid sheet plastic, which is no longer recommended, these materials promote air and water exchange within the soil. Mulches also control temperatures around plants.