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Mushroom at Base of Tree #378427

Asked November 28, 2016, 8:11 PM EST

We have what we believe to be a fruitless mulberry in our front yard that was already a large tree when we bought our home in 1986. In the summer of last year we noticed a large mushroom growing at the base after weeks of rain. This summer after another rainy spell the same type of mushroom appeared again in about the same location. Recently my aunt told me this was a sign the tree is rotting on the inside and therefore the tree is a hazard despite it appearing healthy. I hate the thought of having this great shade tree cut down and I'm afraid we don't have it in our budget at this time to do so anyway. However, at the same time I'm very worried about the possibility of the tree falling on our home or worse our neighbors! Can you please tell me if mushrooms at the roots of a tree are always a sign the tree is rotting inside? Or if there is any way for us to check the tree ourselves to see if it is rotting?

Dallas County Texas

Expert Response

Based on the close up picture of the white/tan growth at the base of your mulberry tree, it appears to be a form of growth known as a slime mold (not considered a true fungus). If it is indeed a slime mold, while unsightly, it likely does not indicate any health concerns for the tree. It is generally brought on by humidity and warmth and is not know to be harmful to plants or animals (it is most common in mulch).

What your aunt is likely referring to is a condition known as Mushroom (or Armillaria) Root Rot, where the presence of mushrooms at the base of a tree does indeed indicate a dying tree. However, these mushrooms (multiple "Armillaria" species can cause this) look quite different from that in your picture. Likewise, trees with true mushroom root rot would likely show some signs and symptoms of disease indicative of overall poor health. The following link, has an excellent explanation of Mushroom Root Rot, pictures to help with identification, as well as signs and symptoms to look for:

http://edis.ifas.ufl.edu/pdffiles/EP/EP47800.pdf

The following link contains an explanation and images of slime mold:

http://plantclinic.tamu.edu/files/2010/09/Slime-Mold.pdf

Hopefully, between these two documents you are able to make a better identification closer up to the specimen.

While it is possible that your tree is not at risk, an inspection by a certified arborist would be your best bet for a definite diagnosis for your tree and any concerns you may have regarding its health.

An Ask Extension Expert Replied November 30, 2016, 12:40 PM EST

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