Mulch conserves soil moisture by preventing hot sun and wind from directly striking the soil and drying it out. Evaporation and therefore water use are reduced significantly. Mulch also insulates, limiting soil temperature fluctuation. In the summer, the plant roots stay as much as 10 degrees F. cooler if the proper amount of mulch is applied.
Many people are familiar with the ‘carpet’ of mulch frequently seen spread out in a perennial bed, but often don’t realize that mulch offers the same benefits spread over the surface of a container. Containers, particularly those made from terra cotta, typically need watering even more frequently than in-ground plants, because the roots can’t reach deeper into the earth for moisture. And container plants are more sensitive to climatic conditions, such as strong winds and blazing sun, because of their restricted environment.
Most mulches, whether organic or inorganic, are common, ordinary materials such as compost, grass clippings, pine needles, shredded leaves, bark, pebbles and rocks. I strongly favor organic mulches because they release nutrients as they break down, thus improving the health and permeability of the soil, and providing an energy source for beneficial soil microorganisms.
Choosing the Right Mulch
From among the many choices of mulch, make your selection based on cost, ease of acquisition and personal taste. Some possibilities:
- Peat moss decomposes slowly and has a reliable pH (3.4 to 4.8) acidity; it is good to add to heavy, high pH soils. Peat moss is particularly beneficial around azaleas, rhododendrons and conifers since these plants require a more acidic soil.
- Decorative bark chips are usually a fairly uniform size and are readily available in bags from garden centers. Bark chips are light to reddish brown in color, durable, easy to use, slow to decompose and quite attractive. Spread bark chips in a 2-3 inch layer if you want to effectively conserve water. All bark chips will turn gray with age.
