A Redditor shared a scary sight last year, documenting a ubiquitous landscaping mistake with a short video, and it’s too bad the scarecrow in the video didn’t keep away the person who did this.
“Is this ‘mulch volcano’ too big for a tree of this size?” they wrote.
“Any mulch volcano is too big for a tree of any size,” one commenter wrote. “There should be a mulched circle out to the drip line but not touching the trunk. The root flare needs to be visible.
“This is true no matter what the size of tree.”
The poster noted the previous homeowner had lived there 27 years, so they thought it might be OK. But then they took matters into their own hands, deconstructing the volcano, removing secondary roots growing in the mulch, and making a mulch donut.
This type of mulch volcano is something many gardeners and homeowners fall victim to, like this Redditor, who also turned to the platform — where people like this user are happy to educate on the issue — for advice.
In an educational and demonstrative video, This Old House showed how mulch volcanoes harm trees — and how to fix them.
Roots need oxygen to breathe, and too much mulch suffocates the root mass and can cause cankers and splitting in the bark — and even kill the tree. Mulch volcanoes may also lead to disease, decay, and insect infestation, among other problems.
Certified arborist Matt Foti told This Old House he likes to spread mulch by hand so he can gauge the depth of it, which shouldn’t exceed two inches.
Proper mulching around a tree keeps grass and weeds at bay and retains moisture in the soil. That’s the key issue: Mulch volcanoes trap moisture around the trunk of the tree, which “inhibits the transportation of oxygen and nutrients by the phloem, effectively girdling the tree,” according to The Tree Care Guide.
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