Horsesugar Leaf Gall
Let me explain. A gall is an abnormal growth on a plant caused by a fungus, bacteria, insects or mites. This gall is called Exobasidium and its caused by a fungus that attacks the new leaves of Horsesugar (Symplocos tinctoria). It doesn’t seem to harm the plant. I’ve been told that it’s edible but I haven’t tried it yet.