Shelf Mushroom on Cottonwood Tree

January 17, 2022


Photographer: Dale Hugo

Summary Author: Dale Hugo

On May 5th, 2004, this cottonwood tree (Populus deltoides) was struck by lightning, damaging about one third of the tree. Sixteen years later, part of it later fell on a neighbor’s house in June of 2020, which unfortunately caused extensive roof damage. Last September, I noticed that about 8 feet off the ground a shelf fungus suddenly appeared. The shelf fungus appears rubbery although it will likely harden over time. My Australian friend called it a conk. Look closely and you can also see a second spherical fungus underneath it. Fungi thrive on decaying, wet wood, so interestingly the mushrooms we see on the surface are actually the fruiting bodies of the mycelia growing inside the tree. The mycelium can be 10 times the volume of the mushroom itself. They aid in the breakdown of the dead portion of the tree. I hope a mycologist can identify the species these two fungi. One thing for sure, I’m not going to eat them!