AgCenter: help trees with proper mulching

Mulching trees is a recommended cultural practice with many benefits, yet too much can literally kill a tree if applied improperly.

A common tendency for some homeowners when winter time arrives is to pile mulch high up around the base of their landscape trees that often resembles a volcano or fire ant mound.  Unfortunately, mulch when piled high up around the base of a tree, can be more detrimental than beneficial.

Typical problems that often result from piling mulch high up around the trunk of a tree include: oxygen starvation of the shallow roots; increased fungal and bacterial infections due to increased moisture around the trunk; a degradation of stem and trunk tissue due to heat buildup from the decomposition of the mulch; a habitat created for various undesired insects, especially fire ants; and as well, a home for rodents. Keep in mind that trunk tissue is quite different from root tissue and cannot survive a continually moist environment. Also, mulch when piled high around the trunk of a tree, decreases the ability for proper gas exchange causing the tree to become highly stressed which often kills the inner bark tissue and eventually the tree.

Proper mulching of trees would include applying the mulch horizontally, and at a depth of 2 to 3 inches rather than piling the mulch vertically up the tree.  Equally important is that the mulch be placed several inches away from the trunk and making sure there is no contact between the trunk and the mulch.

Various types of mulches can be used that work well for trees such as pine straw, pine bark or cypress mulches and, of course, leaves raked from the yard.  Since most shade trees used in Louisiana landscapes are cold hardy the mulching of trees is really not necessary.  But mulching, when used correctly, can be a benefit to trees as a source for maintaining moisture, controlling weeds and providing additional nutrition through decomposition.Rene’ Schmit is the LSU AgCenter County Agent for St. Charles Parish and can be reached at 985-785-4473.


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