Why Maple Tree Bark Turns Black: Fungal Infestation Explained

Black Bark on Maples: A Sign of Fungal Activity

If the bark of your maple trees has turned a uniform, flat black—resembling a coat of matte paint—you’re likely looking at a fungal infestation. Many wood-decay fungi specialize in breaking down the carbohydrates in dead or dying trees, and they often appear as dark, film-like layers rather than the fuzzy growths people expect.

How to Confirm the Diagnosis

The definitive way to identify the fungus is to culture it on laboratory media, but many of these organisms are finicky about their food source and refuse to grow in a lab setting. In practice, the combination of blackened bark and overall tree decline is a strong clue that a secondary fungus has moved in.

What This Means for Your Trees

The fungus itself is rarely the primary cause of the trees’ poor health; it’s usually an opportunist colonizing already stressed or dying wood. Unfortunately, there’s little a homeowner can do to reverse the process. The best course of action is to consult a certified arborist who can assess the trees’ structural integrity and recommend removal or management options.