(NEXSTAR) – It may look like an innocuous garden feature to you, but to arborists, these piles of mulch are an atrocity.
They’re nicknamed “mulch volcanoes” – essentially a mound of moisture-retaining mulch that’s piled up around the trunk of a tree. Well-intentioned gardeners may think this helps a tree get more water, but that volcano could actually be killing the trees in your yard.
“We want to say no to mulch volcanoes,” says Emily Porter with the University of Maryland Extension. “This is happening way too much. It’s an epidemic in our landscapes.”
“These mulch monstrosities have been a source of continual frustration for anyone who cares for trees or cares about trees,” agrees Ohio State University Extension professor Joe Boggs in a blog post. “Yet, despite years of educational efforts, we just can’t seem to stamp out the abominable practice.”
Why are the experts so heated about these volcanoes?
“The problem here is that this mulch is going to create a moist spot around the bark,” Porter explains. “It’s going to encourage roots to grow up on the trunk of the tree, and those roots are going to want to search for oxygen.”
When that happens, the roots can start to wrap around the trunk of the tree, “choking” it, Porter says.
It can also contribute to rot on the bark.
Mulch isn’t the enemy, Porter says, but it needs to be used properly. Photos provided by the University of Maryland Extension help illustrate the right way (on the left) and the wrong way (on the right) to use mulch at a tree base.
“You do want to use mulch to help protect the trunk of the tree and keep the ground nice and moist for the roots of the tree, but you want to spread it out in the root zone and kind of taper it into the trunk.”
You don’t want that mulch layer to be too thick, either. Porter recommends 3 to 4 inches, tapering down toward the trunk and not touching the bark.