Some perennial weeds, such as quackgrass, are extremely difficult to control in the home garden. Quackgrass is a perennial grass that spreads rapidly by underground stems or rhizomes. Rototilling an area infested with quackgrass will simply cut up the rhizomes and spread the weed. To effectively control quackgrass, all the rhizomes must be carefully removed from the soil. Mulches control weeds by preventing weed seed germination.
Mulches control most annual weeds.
Perennial weeds, however, must be controlled by other methods. In addition to weed control, mulches help conserve soil moisture, reduce soil erosion, prevent crusting of the soil surface, keep fruits and vegetables clean, and may reduce disease problems. Mulches may be divided into organic and synthetic materials. Organic mulches include ground corncobs, shredded leaves, grass clippings, straw, pine needles, wood chips, shredded bark, and compost. Synthetic or inorganic mulches include black plastic and landscape mats.