I have a 50-year-old Italian plum tree. The limbs have oyster-shaped growths on them. These growths will not come off–they are hard. Is it a fungus or disease? Or is the tree just getting old?
Hard fungal growths on trees are called conks, a type of bracket fungus, and they are not a good sign. According to The Sunset Western Garden Problem Solver, these growths “indicate a hazardous condition from decay inside.” Usually by the time they are seen, decay inside the tree is substantial and you may need to get an arborist’s help to keep the tree from breaking and dropping branches, and to assess whether it is a danger to structures or people. The Pacific Northwest Chapter of the International Society of Arboriculture provides a listing of local certified arborists. You can also get an arborist referral from Plant Amnesty.