There are several advantages to mulching. Besides the obvious aesthetic benefit, organic mulches help to simulate forest floor conditions for trees. Trees evolved with a deep litter layer of leaves and decaying wood, so planting a tree in a lawn area surrounded by turf is bound to cause problems. A ring of mulch around a tree eliminates the competition for water and nutrients between the tree and the turf. Organic mulches also help build soil fertility and structure. The main problem with mulch it is over applied. Two to three inches are the maximum amount to use. Deep piles of mulch restrict oxygen to roots and actually restrict water penetration to the root zone. This practice also can provide many stem and root rot organisms with an ideal environment to become established. In summary, mulching is one of the most beneficial treatments for trees and shrubs as long as it is done properly.