The Advantages of Mulching

Moisture Retention

Organic and inorganic mulches both help to reduce the amount of necessary irrigation. Hot temperatures cause moisture to evaporate from the soil, necessitating more frequent watering. A mulch provides a protective barrier that minimizes evaporative water loss and keeps the moisture in the soil. Plastic mulches stop evaporation completely so that all irrigation water remains in the garden bed. Organic mulches, such as wood bark and straw, minimize but don't completely stop water loss. Organic materials also keep the soil cooler in hot weather, which further slows water loss.

Mulches made of organic materials, including straw, wood chips, sawdust and compost, add nutrients to the garden bed as they decompose. These mulches typically require yearly replacement. Till the old mulch into the soil to improve both the nutrient quality and the texture of the soil. Garden beds rich with organic matter provide better drainage and moisture conditions compared to those with a low amount of organic matter. Inorganic plastic mulches do not provide any benefit to soil quality.

Plastic mulches almost completely eradicate weed growth in the garden bed. The weed seeds don't receive the necessary sunlight to germinate, and those that do manage to sprout cannot penetrate the plastic. Organic mulches also suppress most weeds if applied in a 2- to 3-inch layer. Some weeds can still penetrate the organic mulch layer or take root directly in the mulch. These weeds tend to develop shallow roots and require little effort to remove if you pull them as soon as they emerge.

Summer annuals require warm soil to grow well. Applying plastic mulch in spring helps warm the soil earlier, allowing for earlier planting and preventing some cold damage. Organic mulches insulate the soil during periods of hot temperatures, protecting roots from overheating. Organic mulch can also protect plants in winter. A thick layer of straw or leaf mulch placed over the top of a perennial plant insulates the soil and protects the roots. The mulch also prevents frost heave, which causes the soil to move and uproot plants during repeated freeze and thaw cycles.