Mushrooms on Trees
Mushrooms growing from the base of a tree or the main trunk or branches are usually cause for concern. Many of these mushrooms, which are actually fungi, can cause the wood in the center of the tree to rot and decay. This decay process can occur in a few months or in some cases, several years. This reduces the overall strength of the tree and it can lead to limbs breaking off during windy periods or entire trees to fall during storms.
Decay is often not visible from the outside of the tree, except where the bark has been damaged or cut. Sometimes fruiting bodies, called conks or brackets, will develop where the tree has been damaged or at pruning scars. Some decaying fruiting bodies may produce mushroom-shaped fruiting bodies at the base of the tree. This can be an indicator of a disease called Armillaria.
Once a tree displays signs of this internal decay, there is not much that can be done to reverse it. There are several things that can be done to prevent it, such as following good tree care cultural practices, which includes proper pruning. It is best not to have grass growing right up to the base of the tree. A tree can be damaged if it is continually hit by a lawn mower or string trimmer, which can lead to an infestation by one of the wood decaying fungi.