Westmont, Illinois – Date Issued: April 20, 2023
With Earth Day and Arbor Day fast approaching, many people are inspired to work in their yards and plant trees. Tree planting activities are common this time of year. However, after your tree is planted, it is important to know how to properly maintain and place mulch around your new tree.
The Village of Westmont Environmental Improvement Committee (EIC) encourages residents to not create a “mulch volcano” around the base of a tree. While some people may think this technique is aesthetically pleasing, they should be aware that this process may actually kill your trees.
Volcano mulching is the practice of piling mulch in an inverted cone up the trunk of a tree. When this happens, moisture gets trapped on the bark and makes the tree highly susceptible to disease and decay. Damaged bark may develop cankers, or wounds, and large limbs, leaves, and other parts of the tree above a canker may die. Mulch volcanoes can also damage a tree’s root system.
Mulching, when done correctly, offers many benefits to trees. Mulch mimics nature by creating a layer of organic material under the spread of a tree. In the woods, fallen leaves, branches, and herbaceous plants cover the ground, which is good for a tree. This organic matter is called leaf litter and it retains moisture, insulates the ground, slowly decomposes, and enriches the soil. There’s an entire ecological system in leaf litter, complete with food webs, unique biochemistry, and micro-climates. Ideally, mulch should be spread within a 3’ to 10’ circle around the tree. The height of the mulch should be 2” to 4” deep around the tree without touching the trunk of the tree.
Additionally, mulch volcanoes shed water like an umbrella. Even in years with lots of rain, an improperly mulched tree may not get moisture where it needs it because the rain runs off the sides of the volcano. Mulch volcanoes can also turn “sour.” This is caused by anaerobic conditions (lacking oxygen) created by thick layers of mulch. The organic material heats up, becomes highly acidic, and smells sour. This acidic mulch burns the tree’s bark. This is especially harmful to young trees that haven’t developed thick bark.
If you employ a lawn service, homeowners are encouraged to talk about this problem with the landscaper and maintenance crews to prevent mulch volcanoes. For more information regarding proper tree care, contact us at green@westmont.il.gov.
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