As summer fades into fall, gardeners consider tidying their flower beds and around their trees and shrubs. Putting down new mulch can be part of this process, and it raises the question: How much mulch? Mulching two to three inches in total depth is plenty, making sure to keep the mulch from touching plant stems, and not piling up volcanoes of the stuff around trees. Any “professional” landscaping outfit or individual who does otherwise is acting out of either ignorance or the desire to sell more mulch, perhaps both.
Another consideration is whether to put down commercially produced mulch or wood chips. The term “mulch” can apply to organic or inorganic ground covers, such as pine bark, shredded hardwood, or stone. Wood chips are made from every part of a tree, and chips range in size from coarse chunks to finely ground pieces no larger than an inch. Gardeners should be careful to check the source of wood chips because they may have come from trees infested with beetles or borers, and if the chips have not been ground up finely enough or heat treated, then the insects may survive to cause further damage in new surroundings. Commercial wood mulch should not cause similar problems if the manufacturer has effectively screened it for pests, though gardeners should not apply it directly up to the foundation of a house, where it can serve as cover for termites already present in the soil.
A good rule of thumb to follow when applying mulch is not to apply it so thickly as to make it a heavy slog for the average happy garden gnome pushing a wheelbarrow.