A: When listener Kathy first sent me this picture, I was fairly certain this was slime mold. Some are spotting creeping along mulch, plants, and even concrete.

However, when Kathy consulted a certified arborist (which is a smart move when it comes to concerns about the health of large and potentially damaging trees like this oak), she and I learned that the weird formation is ‘oak bracket’ or ‘weeping conk’. Much like a mushroom, this is a fungus and unfortunately, causes decay at the base of the tree and root rot, even before symptoms are visible.

These globs ooze an amber-colored liquid in the warmer months and then dry out as the weather cools, often becoming a dull orange and cracking. Aside from this obvious concern, Perdue University Landscape Report explains that the “infected trees [will exhibit] stunted growth, limb dieback, and/or sparse, off-color foliage.”

Most mushrooms (ie: fungi) signal some weakness or illness in a tree. Slime molds on the other hand aren’t a fungus. They aren’t capable of causing disease and simply thrive when moisture is present.

If you’re concerned about something unusual in or around your trees, please contact a certified arborist. You can find one here. They’re great people!

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