Mulch can be spread thickly if water can penetrate it to reach the soil and if it does not smother the roots of the plants 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. Mulch should be kept a few inches away from the trunks of trees and shrubs to prevent damage to the plants from disease and rodents. The best place to look for mulch materials is in your own yard.
Every yard has grass, leaves, other green materials, or woody materials that can be made into mulch.
If chipped or shredded woody wastes are needed, contact tree services listed in the Yellow Pages. Services working in your area may be willing to deliver woody wastes to avoid extra travel and dumping expenses. Some wood shops and coffee roasters make their organic by-products available to customers and the general public. Large gas-powered chippers which are able to handle woody wastes up to 6 inches in diameter are available at rental shops. In general, the larger the machine, the faster the mulch-making.