Mulching is a valuable technique that's been used by gardeners for centuries. It provides moisture and temperature regulation for plant roots and soil, prevents or slows erosion, keeps competitive weeds at bay and keeps planting beds looking tidy. Organic mulches such as shredded bark, leaf mold or compost have the added benefit of enriching the soil over time, as the mulch breaks down and its component nutrients are released into the soil. Inorganic mulches like rubber, plastic or stone are used primarily to hold moisture and soil in place, and do not require frequent replenishment. Most plants will benefit throughout the year from this protection.
Apply organic mulch around the base of individual plants, covering the full diameter zone. Alternatively, cover the entire soil surface in garden beds and borders with multiple plants. Mulch around the bases of trees and shrubs out to past the drip line to cover the soil carrying the bulk of the plant roots. Apply with a shovel or your hands, and create a level layer with the tines or back of a rake.
Place the mulch under the plant several inches out from the main stem or trunk, and continue the mulch layer to out past the drip line of the plant. Do not push mulch right up against the plant trunk or stem, as this can trap moisture and create conditions for disease. Depending on the size of the plant or tree, a buffer of several inches is sufficient. The smaller the plant, the smaller the mulch-free buffer zone should be.
Lay mulch in an even blanket over the soil in depths from 1 inch to 4 inches. Typically 1 to 3 inches is adequate for moisture retention, erosion control and temperature regulation. Mulch up to 4 inches deep when protecting plants, roots and bulbs from cold winter temperatures and wind. Mulch up to 4 inches in warm and dry climates for plants that prefer cool roots.