Mulch helps conserve water by reducing evaporation, allowing water to be held in the soil for longer. It also helps build soil structure, inhibits weed growth, and much more. Mulch is applied as a layer on top of the soil, typically 2-3 inches deep. It is important that the mulch layer does not go all the way to the base of the stems or trunks of plants. A distance of at least three inches should be maintained from the main stems or trunks of plants to avoid holding too much moisture at the sensitive root crown area where stems or trunks meet the soil.