Consider What Mulch Does
Mulch has many benefits for a yard and garden. It helps the soil retain moisture, which means you don’t have to water plants as frequently as you would otherwise. It also promotes microorganism activity, which leaves soil less compacted so nutrients are better able to reach plant roots. The right mulch also can regulate soil temperature and fight weed growth that can rob desirable plants of moisture. Mulch can limit soil erosion, too. It gives a landscape a finished, polished appearance as well.
Consider Your Landscape Needs
Your landscaping needs can help you choose between rock and wood mulch. If you want to improve soil conditions, wood mulch is the best option because it provides a rich environment for microorganisms and earthworms. It also provides an effective protection from lawn mowers for trees and shrubs. On the other hand, rock mulch is a better option if your garden has trouble with diseases because rock mulch doesn’t harbor bacteria or fungi. Rock mulch usually works best in non-plant areas, however, because it retains heat so may cause water evaporation in plants. It also makes areas adjacent to it significantly warm in afternoons and evenings. So although a patio made of or surrounded by rock mulch may feel uncomfortably warm on summer evenings, the rock mulch can keep the patio comfortably warm during early spring and late fall nights.
Consider Where You Will Place It
The area where you will place the mulch also factors into the decision of whether to use wood or rock mulch. Wood mulch is ideal for placement around shrubs, trees, small fruit plants and perennials because of its soil improvement and water retention abilities. It is a poor choice in open, windy areas, though, because it is blown easily. Rock mulch is an effective alternative in windy areas because its weight helps keep it in place. It is also a decorative option in rock gardens and succulent gardens. Rock mulch works for driveways and walkways as well. Avoid using it in areas beside a lawn, though, because it may be kicked up by a lawn mower and ruin the mower's blades.
Consider Your Budget
Your budget may affect your choice between wood and rock mulches. Wood mulch is usually less expensive than rock mulch, but wood mulch usually requires replacement every one to two years because it breaks down easily and, as mentioned, can blow away. Rock mulch involves a larger initial investment than wood mulch, but it doesn’t decompose or blow away. So it doesn’t need to be replaced every few years.