Syn. Polyporus squamosus. It causes a white rot in the heartwood of living and dead hardwood trees. This mushroom is commonly attached to dead logs or stumps at one point with a thick stem. Generally, the fruit body is 8 to 30 cm across and up to 10 cm thick. The body can be yellow to brown and has 'squamules' or scales on its upper side. On the underside one can see the pores that are characteristic of the genus Polyporus; they are made up of tubes packed together closely. The tubes are between 1 and 12 mm long. The stalk is thick and short, up to 5 cm long. The fruit body will produce a white spore print if laid onto a sheet of paper. They can be found alone, in clusters of two or three, or forming shelves. Young specimens are soft but toughen with age. The mushroom's smell resembles watermelon rind.
It is particularly common on dead elm and is also found on living maple trees. It commonly fruits in the spring, occasionally during autumn, and rarely during other seasons.