A common mulching mistake has pervaded landscaping trends, and expert gardeners are urging homeowners to understand the harm it can inflict on trees.
“‘Volcano mulching’ is still a thing with landscapers despite decades of evidence showing how bad it is for trees,” the Cornell Cooperative Extension Onondaga Master Gardener Program wrote in a post to its Facebook Page.
Volcano mulching is when mulch is piled up to look like a volcano on the base of a tree. Many landscaping enthusiasts have adopted the trend, believing that more mulch will protect their trees from weeds.
“Volcano mulching” is still a thing with landscapers despite decades of evidence showing how bad it is for trees. Mulch…
Posted by CCE Onondaga Master Gardener Program on Friday 20 June 2025
Mulch is a powerful resource for landscaping as it can act as a barrier to weeds without harsh chemicals, insulate trees, and create an effective fertilizer to keep soil healthy. Some find mulch volcanoes aesthetic.
One commenter on Facebook wrote beneath the original post that they went to a house where they took “pride and joy into their garden” that had a massive maple tree with a mulch hill piled four feet high.
Too much mulch piled up can cause far more problems for plants, sometimes furthering the very same issues mulching is meant to fix, all the while leading to a costly mistake.
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Birds & Blooms explained that too much mulch can lead to root rot and give cover to rodents such as mice, chipmunks, and voles that chew on tree bark. Others described how mulch volcanoes can block oxygen from reaching trees.
Meanwhile, the trend can encourage disease by blocking out air and the sun. The issue of “stem girdling roots,” where roots grow around the tree trunk and merge with its stem tissue, can restrict vascular flow and kill trees.
Experts still encourage gardeners and landscapers to opt for mulch as a useful alternative to using chemicals in the garden. But they emphasize that proper mulching is necessary to get the optimal benefits from the resource.
“Mulch should be raked away from the trunk,” the expert gardeners said in the Facebook post. “[It] should be applied no more than three to four inches deep.”
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Commenters under the post agreed that this gardening trend has gone too far.
“It is so prevalent. I can’t understand why,” one concerned commenter wrote.
Another mentioned that landscaping this way is their “Major pet peeve.”
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