A very distinctive shelf-like fruiting structure forms singly on the wood at or near the soil line. It is brown to reddish brown on top with a cream to white-colored margin. The brown portion appears to have been varnished. The shelf grows perennially for 5 to 10 years and may reach 8 to 12 inches across. The underside of the shelf is light colored with millions of tiny pores in which the spores are formed.
Infected trees slow in growth rate, have branches dying, and their leaves are small and yellowed.
Although it may require several years for the tree to die, an infected tree poses a hazard. This fungus can cause a root and butt rot particularly on oaks. Trees may topple before any obvious symptoms are noted. Infected trees often have a branch dieback, and fewer than normal leaves that are yellowed. Although the root rot begins well out on the root system, the fungus eventually reaches the butt of the tree where it forms large , tough, irregularly shaped gray to light brown or dark brown shelves at or just above the soil line.