The Town of Canandaigua is asking residents to avoid a common but harmful landscaping mistake known as “volcano mulching,” where mulch is piled high against the trunk of trees. The practice, often seen in commercial landscapes, can damage or even kill trees, according to a public advisory issued by the town and its Tree Advisory Board.
“Mulch should not touch the trunk of the tree,” the notice states. “The trunk was simply not meant to be covered, and doing so invites decay and pests; it may kill the tree.”
The advisory highlights several dangers of volcano mulching, including:
- Increased disease and decay due to moisture trapped against the trunk
- Attraction of insects and rodents
- Girdling roots that can strangle the tree
- Soil conditions that are too damp or compacted for roots to thrive
- Inhibition of the root flare development, making trees more likely to fall during storms
The root flare—the area at the base of a tree that widens before entering the soil—should always be visible, the advisory explains. When covered by mulch, this vital structure is hidden and the tree’s overall stability is compromised.
Proper mulching, however, offers many benefits. Residents are encouraged to spread mulch 2 to 4 inches deep, ideally in a ring or “donut” shape that keeps it away from the trunk. A common guideline is the “3x3x3 rule”: 3 inches of mulch, placed 3 inches from the trunk, in a 3-foot-wide circle.
Preferred mulching materials include bark, wood chips, and leaves—never stones or other inorganic products. Benefits of appropriate mulching include moisture retention, weed suppression, soil improvement, and temperature regulation around tree roots.
The Town of Canandaigua, recognized as a Tree City USA community, hopes this public awareness effort helps residents protect their trees and landscapes for the long term.
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