Hay, straw, sawdust, ground bark, leaves, compost and even newspapers are among the many substances used as organic mulches. All reduce weed emergence and make it easier to pull those weeds that do emerge. Some weeds such as nutsedge will grow through mulch, even through plastic mulch. Inorganic mulches include black and other opaque plastic, as well as landscape fabric. Landscape fabric is much more expensive than plastic mulch but has the advantage of allowing water to pass through into the soil.
Black plastic is the most commonly used inorganic mulch.
Clear or translucent plastic should not be used as a mulch because weed seeds will grow under it. Black plastic eliminates growth of most, but not all weeds except through the holes cut for vegetable growth. The main reason why herbicides are not used as much as mechanical or cultural weed control methods in home gardens is that suitable herbicides are seldom legally available in small economical amounts. Several other difficulties also exist with the use of herbicides by home gardeners. Many herbicides are non-selective and will kill both vegetables and weeds.