Mulch
Adding Mulch
Landscape mulch adds an attractive finish to the landscape, reduces weeds and helps to conserve water. Various mulch options are available but can generally be divided into two categories: organic and inorganic mulches.
Organic mulches
Organic mulches are products derived from plant material. This can include wood chips, shredded bark, straw and grass clippings. Wood chips are the most common organic mulch in our area and they insulate our soil better than inorganic mulches. Though the surface of wood mulch can be nearly as hot as concrete or asphalt, the soil beneath is significantly cooler, reducing evaporation from the soil. Over time organic mulches break down, adding nutrients to the soil and improving soil structure. As such, top dressing the mulch may be necessary every few years. Most trees and perennial flowers will greatly benefit from organic mulches. Many desert species like cactus and yucca, however, may do best with inorganic mulch.
Inorganic mulch
Inorganic mulch generally refers to gravel but may also include tumbled glass or rubber. Gravel comes in a range of colors and sizes allowing for creative designs by using contrasting textures. Unlike wood mulch, gravel does not break down rapidly and rarely needs top dressing. As such, it does not improve the soil over time. Additionally, though gravel does provide some insulation of the soil, it is much less than wood mulch. Many native desert species prefer these kinds of harsh conditions with limited nutrients and soil that dries out between irrigation cycles.
The use of weed fabrics and plastics is discouraged in most situations. Around plants, weed barriers tend to smother the soil by reducing air and water movement in the soil. The weed deterrent benefit is usually short lived and weeds will begin sprouting on top of the fabric within a few years. Limit weed barriers to pathways or extremely sparse planting areas. A 2”-4” thick layer of mulch, either organic or inorganic, reduces weed germination without harming the soil.