There are two types of mulches, organic and inorganic. Organic mulches include wood and bark chips, straw, grass clippings and seed hulls. Inorganic or inert mulches include weed-barrier fabrics, gravel and rock.
The ideal mulch does not compact readily. It does not hinder water and air movement into the soil, it is not a fire hazard, and it breaks down slowly. In addition, the ideal mulch is uniform in color, weed-free, attractive and does not blow away.
The selection of a mulch depends on its intended use. Consider the size of the area in relation to the cost of materials and availability (Table 1 in the "FULL ARTICLE"). Table 2 (In the "FULL ARTICLE") lists advantages and disadvantages of organic and inorganic mulches.
If appearance is the main goal, inorganic or inert mulches may be the best choice. If the main objective is soil improvement, consider an organic mulch that gradually breaks down. If the area is used primarily for annual flowers, it often is more practical to use a temporary organic mulch, such as composted leaves or grass clippings, that can be turned under each fall.
Mulches can be used to prevent soil erosion by wind and rain. In windy areas, gravel or rock mulch may be preferred over lightweight organic mulches. Any mulch that reduces the impact of raindrops will help reduce water erosion, just make sure the soil surface is entirely covered with mulch.
Black plastic (polyethylene) is not recommended as a mulch in landscape areas. Black plastic is impermeable therefore no oxygen exchange can occur in the soil. Lack of oxygen to the roots significantly reduces plant growth. Black plastic also prevents water penetration. If a weed barrier is needed, use landscape fabrics instead to allow water and oxygen exchange.