Mulching trees can be one of the most beneficial things a homeowner can do for the health of a tree. Mulch can reduce water loss from the soil, minimize weed competition and compaction, and improve soil structure, fertility and health. If applied properly, mulch can give landscapes a handsome, well-groomed appearance.

Problems occur when mulch is applied too thick and piled high on trunks and stems. Sometimes improper mulching looks like mountainous mulch volcanoes at the base of trees. When this is done, it creates a moist environment in which opportunistic decay fungi attack the trunk and roots, causing root rots, crown dieback, a decline in health, and tree failures. Over-mulching also prevents gas exchange, suffocating roots and stems; can lead to rodent chewing and stem girdling; nutrient deficiencies; and often causes roots to grow up into thick mulch, only to dry out in hot summers, or form girdling roots that encircle and kill trees.

When applying mulch, it is important that we not cover that trunk flare (taper) with soil or mulch. Spread the mulch out in a layer that is no thicker than 2-4 inches, and don’t pile it up on the trunks of trees and stems of shrubs.

For more information on Proper Mulching visit the following sites

Mulching Trees

ISA Mulching Fact Sheet

Mulching Fact Sheet

An in-depth look at mulches in landscapes

Good info on mulching of trees

Problems with Over-Mulching Trees and Shrubs

What Is Growing in my Landscape Mulch?

Mulch Website at the University of Missouri Extension

Deep Roots in the Landscape Research – Morton Arboretum

Cornell University Factsheet on Mulching