Is this fungus/mushroom harmful for our maple? #816950

Asked November 27, 2022, 2:39 PM EST

We recently noticed this fungus/mushroom growing on a large silver maple. I believe it appeared or grew to this size sometime in the past few weeks. We hoping to find out what this is, if it is harmful to our maple, and if it should be removed. Thank you!

Frederick County Maryland

Expert Response

That is a type of mushroom referred to as a 'bears head' or 'lions mane'.  Unfortunately, it is a sign of heart rot within the tree.
You can see a large area to the right in your first two photos that looks like a deep split.
We think that it's a good idea to contact a tree health expert, a.k.a. an ISA-certified arborist to do an on-site evaluation of the tree and its structural integrity. You should do this sooner rather than later if its fall would threaten people or homes.
This page from our website can help you to find an arborist and learn signs of a tree's decline:

Arborists are usually on staff at larger tree companies or you can search for one at the credentialing agency at .

Christine McComas Replied November 28, 2022, 12:34 PM EST

Thank you Christine. We really appreciate the feedback, we just had an arborist out to assess the tree and plan for trimming branches which may be at risk of falling toward our roof. We also removed the lions mane from trunk. The mushroom was just massive - the pictures didn’t do justice and I weighed it out of curiosity… 19.2lbs!

Thanks again,


The Question Asker Replied December 12, 2022, 2:55 PM EST
You're welcome.
Wow, that is an impressive mushroom! The fungus that produced it is still growing within the tree (mushrooms for fungi are like flowers for plants...they can be removed without killing the whole organism, which in the case of fungi is a network of tissues inside what it's feeding on) so you might see more when the fungus is ready to produce them and the weather conditions are suitable.

Mira Talabac Replied December 12, 2022, 5:21 PM EST

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