Using an organic mulch such as wood chips around trees and in shrub beds will provide several benefits. A four inch layer of mulch under trees and around shrubs and perennials goes a long way to keep plants alive and healthy.
Mulch helps to regulate soil temperature resulting in less stress on plants between hot,
dry summer days and freezing winter nights. Mulch allows for less and easier weeding of beds. Organic mulches, as they gradually break down, add nutrients to the soil. Mulching around the base of trees also keeps the lawn mower and weed eater from damaging the bark of trees.
Most importantly, mulching reduces water usage. A mulched area under low-water-use trees with dryland shrubs or perennials can reduce water usage by as much as 50 percent from the water needed to maintain a bluegrass lawn.
Mulching mature trees to their drip line is beneficial as well. For a larger-sized tree this may extend a mulch circle outward from the trunk 20 feet or more, greatly reducing the amount of lawn. Having mulch to that point helps retain moisture in the root area.
Weed the area to be mulched before applying the mulch.
Spread mulch around any plant as far as the distance of its outmost branching (this is called the drip line) or cover an entire garden bed.
Mulch can be spread thickly if water is able to penetrate and if it does not smother the roots of the plant being mulched. Three inches of mulch is safe for any woody plant, and up to eight inches can be used for large trees.
Thick mulches are harmful to shallow-rooted plants such as rhododendrons and azaleas.
For any woody plant, apply mulch starting 3 to 4 inches away from the trunk to prevent mice from eating the bark.