A large rosette of whitish to cream caps arising from a tough, gnarled base at the foot of oaks and other hardwoods, where it causes a white stringy butt rot. Despite looking like a polypore, it is related to Russula and Lactarius, which shows in its round, spiny, amyloid spores.
Edibility disputed; not recommended. Young, tender cap edges are widely eaten after thorough cooking, but it turns tough, woody and bitter with age, and some field guides list it as inedible or warn of digestive upset or allergic reactions. If tried, eat only a small amount at first. See Notes for look-alikes.
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Habitat
Parasitic on hardwoods, especially oaks (also maple and other hardwoods), causing a white stringy butt rot of roots and lower heartwood; also saprobic on stumps. Alone or in groups at tree bases, summer and fall.
Distribution
North America east of the Great Plains, occasionally reported from Mexico; Wikipedia also lists Europe, Asia (including Guangdong and Hunan, China) and Africa. Western North American conifer material is Bondarzewia occidentalis.
Characteristics
Fruiting body: 20-50 cm or more across, of one to several spiraling caps from a single stem-like base. Cap: 6-25 cm, kidney-shaped or irregular, flat to centrally depressed, dry, velvety or leathery, sometimes radially wrinkled but never scaly; white becoming cream to dull yellowish or brownish. Pores: decurrent, whitish, not bruising or faintly yellowish to brownish; round, 1-2 per mm, becoming angular; tubes shallow. Stem: 4-10 cm long, 3-5 cm wide, off-center and poorly defined, tough. Flesh: white, thick, not bruising. Spore print: white. Spores: 6-7.5 µm, globose to subglobose, with amyloid spines or ridges 1-2 µm long.
