Posted on: April 17, 2019[ARCHIVED] EIC Alerts Residents To Volcano Mulching Concerns
Westmont, Illinois
Date Issued: April 17, 2019
Earth Day is Monday, April 22, 2019 and a lot of people are inspired to plant trees. Tree planting activities are common to celebrate this special day. 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 stop “volcano mulching”. 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. Volcano mulching is a familiar sight throughout the suburbs and can be found along parkways, in yards, and in gardens. The intention may be good, but the practice of volcano mulching is harmful to trees.
When mulch is piled up against the tree trunk, 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.
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.
Volcano mulching also wreaks havoc on root systems. It causes some roots to suffocate, reducing overall water intake. It also encourages roots to grow up into the mulch layer, instead of down into the soil. During drought years, roots need to tap deep into the soil where the moisture is, but if they’re up in the mulch layer they get little but air. Thus, the mulch intended to retain moisture may actually cause the tree to die.
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.
Also, mulch volcanoes may 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.
Another issue with volcano mulching is the type of mulch used. Not all mulch is created equal. The composition of mulch is very important for plants because each type of mulch has unique chemistry, water retention properties, and decomposition rates.
In nature, this is all taken care of, but a gardener must match the mulch with the need. In landscaped settings, the ground under a tree may be a thin layer of turf grass or bare soil. Mulch is added as a ground cover to achieve some of the benefits that natural leaf litter provides in the woods. It helps to hold moisture, suppress weeds, and insulate the soil from extreme heat and cold. It also protects trees and shrubs from overly zealous gardeners with lawns mowers and weed whips.
If you’re planting a tree this month, be kind to the tree and give it just the amount of mulch it needs. It can live to see many more Earth Days, if given a good start. For more information regarding proper tree care, contact us at green@westmont.il.gov.
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Contact: Larry McIntyre
Village of Westmont
Communications Director/PIO
630-417-0280
lmcintyre@westmont.il.gov
