there are mushrooms growing out of a whole where there use to be a limb-- is this bad for the tree??
The mushrooms that you see growing from the tree are most likely there because there is dead wood where the cut was made. The mushrooms simply are decaying the dead wood. In and of themselves they aren't causing damage to the live wood. But they may be an indication that dead wood has spread deep within the heart of the tree. It might be wise to have a professional arborist look at it if it poses a possible hazard to any structures.