Syst. mycol. 1: 347. 1821.
Common Name: none
Synonyms: Polyporus decurrens Underwood; Polyporus mcmurphyi Murr.
Fruiting body annual, cap 50 to 150 mm broad, round to semicircular in outline, convex, becoming plane, depressed to infundibuliform; margin incurved when young, sometimes upturned in age; surface buff, ochre, tawny to brown, covered with dark fibrils and scales, the latter often with erect tips; context pallid, up to 10 mm thick, tough, hard when dry; odor and taste not determined.
Pores white, cream, to pale tan, 2-3/mm, round, angular, to irregular in shape, edges entire to dentate; tube layer 1-3 mm in depth, concolorous with the pores.
Stipe 30-70 x 15-30 (40) mm thick, solid, fleshy-tough, round, equal to enlarged at the base, cap attachment central, eccentric to occasionally lateral; surface concolorous with the cap or lighter, pores descending the apex a short distance, sometimes leaving reticulations; terrestrial fruitings attached to a belowground dark brown to blackish, irregularly shaped sclerotium.
Spores 10-16 x 4-6.5 microns, oblong-cylindrical, smooth, thin-walled, hyaline, inamyloid; spores white in deposit.
Mostly solitary, terrestrial, occasional on downed wood of various hardwood trees such as oaks (Quercus spp.), willows (Salix spp.), and madrone (Arbutus menziesii) etc.; fruiting after fall rains along the coast; uncommon.
Young specimens edible if thoroughly cooked; sclerotium inedible.
Polyporus tuberaster is a ground-dwelling polypore (with some exceptions) that from a distance could be mistaken for a gilled mushroom. The cap is buff, tawny to brownish, covered with small dark scales, often with raised tips. A whitish, decurrent pore layer and central to eccentric stipe are also helpful fieldmarks. Fruiting bodies of Polyporus tuberaster are unusual in that they develop from an underground blackish potato-like tuber called a sclerotium, thought to be a resting stage or storage structure. Apocryphal stories aside, the blackish potato-like tubers are not edible, because of a tough texture and embedded dirt. Polyporus tuberaster is occasionally found on downed wood. Whether a mycelial connection exists from these fruitings to a buried sclerotium is unknown. Polyporus tuberaster can be confused with Polyporus squamosus, a similar but larger, strictly wood-dwelling species that has caps with coarser scales but these typically lack erect or tufted tips. Additionally a sclerotium is not produced. Several members of the genus Albatrellus, another ground-dwelling polypore are also similar, but none have the combination of cap colors and scales of Polyporus tuberaster.
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