Generally used in a landscape around the bases of trees, shrubs and other plants, mulch shades and cools the ground around the plants, helping to retain moisture in the soil by the plant’s roots. If you do not want to use mulch in your landscape, or simply prefer the look of stone, you can use rocks instead of mulch around plant bases. Unlike mulch, however, the rocks actually absorb heat and increase the moisture loss in the soil.
Use rocks instead of mulch only around plants that have a high drought-resistance. This includes many trees, shrubs and cacti, but excludes many flowers. The drought-resistance of a plant is generally listed on its information tag.
Build a border wall around the plants that you want to mulch with rocks. A border wall prevents rocks from getting spread into undesirable locations, such as driveways.
Layer rocks to a depth of 1 to 2 inches around the base of newly established plants to ensure that they don't receive too much heat and lose too much water at night, which may prevent the plants from growing. Layer rocks around established plants as high as the edge of the border wall to achieve the look that you desire.
Water plants as usual through the rock mulch. Apply the water over the rocks and it sinks down through the rocks and into the soil.