Mulch prevents water and wind erosion and stabilizes soil temperatures (warmer in winter, cooler in summer under mulch).

It also reduces evaporation of moisture from the soil, reduces weed competition with landscape plants, and prevents damage to trees and shrubs caused by lawn mowers and string trimmers.

Mulch creates a better environment for many beneficial soil organisms. As it decomposes, it improves the soil.

It also reduces soil compaction, increasing infiltration of water and air into the soil.

This results in healthier tree and shrub roots and healthier trees and shrubs.

These benefits also help herbaceous perennials.

Don't mound mulch up against the trunks of trees and shrubs. Those volcano-shaped piles may look good to some, but they can kill your trees.

Instead, spread the mulch about 3 to 4 inches deep in a circle at least 3 feet in diameter around young trees and shrubs. Then brush away mulch at the center of the circle so that it is several inches from the base of the tree.


A slight depression in the center is OK. Think lunar crater -- not Mt. Vesuvius.

Even if you keep it away from the trunk, spreading mulch deeper than 4 inches can create shallow, vulnerable root systems. As your trees grow, extend the mulch to their dripline (the edge of the canopy).

Trees benefit more from extensive mulching. You're not doing them any favors by piling it higher and deeper.