Fruiting body annual or short-lived perennial, 2-10 cm broad, 0.5-2.0 cm thick, at first resupinate, then forming sessile, fan-shaped, tiered brackets or occasionally rosettes emanating from a common base; surface tomentose, concentrically-zoned, often multi-colored, cream, pale-buff, dingy yellow-brown, or greyish-brown, in age sometimes green from encrusted algae; flesh thin, pliant, becoming tough, cork-like, white, unchanging; odor and taste mild.
Gills white, radiating from attachment point, broad, tough, cream-colored.
Spores 4-6 x 1.5-2.0 µm, smooth, cylindrical to elongate bean-shaped, nonamyloid; spore print white.
Scattered to clustered in overlapping shelves on hardwood logs, but not limited to birch as the the species name would suggest; fruiting from early to late winter.
Inedible; too tough for the table.
Lenzites betulina would be just another polypore, except that the the spore-bearing surface is gill-like, not poroid. Despite this apparent similarity to fleshy, gilled, mushrooms, Lenzites betulina is a polypore with the characteristic leathery toughness one would expect of a member of this group. Another polypore, Trametes versicolor has a remarkably similar, zonate, tomentose, upper surface, but is easily distinguished by a poroid hymenium. Less common than Lenzites betulina is Gloeophyllum saepiarium, which also has a gill-like hymenium, but is rusty-brown in color, and grows on conifers as opposed to hardwoods.