Q: What is this? Itโs growing at the base of our palo verde.
A:ย That is a Ganoderma fungus and unfortunately itโs not a good sign. The part you see is the fruiting body of the fungus and the rest is inside the tree. It begins as a root rot that infects the tree from a wound of some sort. The fungus is found in the soil. Once it is in the tree there is nothing you can do to treat the problem. A tree that is rotten on the inside is a liability. The tree may live a bit longer but its days are numbered. I canโt see the whole tree from your photo so it would be good to have an arborist examine the tree in person to determine the gravity of the situation. If this tree is of significant size and location that it could harm people or property nearby if it fell, you should look into having the tree taken down soon. Consulting a couple certified arborists would be wise to get multiple estimates on the potential cost and timing for this operation.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
