Is Red Mulch Harmful Around Trees?

Sources

• The origins of red mulch directly affect if any potential harmful components exist. In the United States, certification and legal definitions explain what may be sold and labeled as mulch. Closely look at packaging information or ask the supplier of loose mulch about the mulch's origins. Mulch made from felled trees are fully organic. By contrast, mulch made from destroyed building materials may contact residues of paint, absorbed petroleum or other contaminants and retain heavy metals under the red dye coating. You definitely don't want to place inorganic mulches over trees that produce edible food crops, such as apples or cherries.

Benefits

• Red mulch around the base and under the canopy of a tree provides many benefits. Mulch deters weeds, conserves soil moisture, diminishes soil compaction, moderates soil temperature and decomposes to provide trace minerals for tree roots to absorb. Lastly, the rusty red color of the mulch is attractive and helps dress up the borders, beds and edges in a landscape to make it more pleasing to the eye.

Caveats

• The Morton Arboretum cautions property owners about bad practices when applying mulches around trees. The proper method is to lay a 3- to 4-inch layer of mulch in a wide ring around the trunk, not letting the mulch directly contact the trunk and basal root flare. Avoid creating a cone-like mound or "mulch volcano" around the tree's trunk. This excessive pile of mulch prevents air circulation and favors fungal rot. Once a tree is infested with rot, it's difficult to impossible to fully treat or correct. The pile of mulch also is a nook or habitat for insect pests to flourish. If the soil around the tree is always soggy and slow to drain, don't use too much mulch as slows drainage reduces oxygen in the soil.

Tree Root Insight

• While it may look attractive and tidy to merely place red mulch in a small ring right around the tree trunk, the tree's roots radiate outward far from the tree. This is where the tiniest growing roots exist in the topsoil. Mulch that far out prevents weeds and lawn from robbing the tree's fibrous roots from moisture and nutrients.