One homeowner recently turned to the r/Arborists subreddit for advice after growing concerned about the health of one of the trees in their yard.

"Maple in front yard has this going on at the base," the poster wrote. "A brief search says slime Flux and that it's not really treatable. I'd hate to lose the tree. I did not plant it, trunk is about 12". I feel like the fact that it seems like it's on a mound may have something to do with it. My tree knowledge is minimal."

As several commenters were quick to jump in and point out, the problem was, of course, the dreaded "mulch volcano" — a term used to describe the common but misguided practice of piling mulch high around the base of a tree.

"Remove the mulch volcano, cut out the adventitious roots. Hundreds of posts on the tree subs with this problem, scores if not hundreds of posters with photos of before and after when they did this very task," wrote one (possibly a little bit exasperated) commenter.

"Second this. Get rid of the mulch at the base. Let the root flare breathe," another chimed in.

"Slime flux discoloration is different. That's more than likely a bleeding canker," a third commenter contributed.

Although the creators of mulch volcanoes — who are often, surprisingly, professional landscapers — are probably well-intentioned, hoping that the pyramid of mulch will protect the tree; in reality, it does the opposite. By not allowing the tree's root flare to breathe, the mulch volcano traps moisture against the trunk, leading to rot and giving access to insects that can damage the tree.

The mulch volcano can also often confuse the tree's roots into growing upward and wrapping themselves around the trunk instead of down into the dirt. This deprives the tree of essential nutrients while also basically strangling itself with its own roots.

Luckily the fix is a relatively easy one: As the first commenter said, remove the excess mulch and allow the root flare to breathe.

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