Summary: Features include chalky white hoof-shaped to columnar fruitbodies on conifers, chalky white flesh, crumbly consistency, and extremely bitter taste. This is a source of agaricin (agaric acid) or 2-hydroxynonadecane-1,2,3-tricarboxylic acid, which has been used in the past to inhibit sweating, for instance the night sweats of the tuberculosis sufferer. The quinine-like bitter taste also caused people to falsely attribute anti-malarial properties to it. With Phaeolus schweinitzii and Porodaedalea pini it is said to be one of the three major destroyers of standing coniferous timber in the West of North America. The name Lariciformes officinalis was supported by molecular evidence in the study of Han(1) but was not the current name in the online Species Fungorum, accessed November 23, 2019 or MycoBank, accessed the same day.
Fomitopsis officinalis has been found in BC, WA, OR, ID, AB, ON, AK, AZ, CA, CO, MI, MT, NM, NV, SD, and WI, (Gilbertson).
Cap: 4-30cm wide and 5-40cm or more high, starting as a knob, becoming convex then hoof-shaped to cylindric, hard and tough when old; white to yellowish but aging grayish and sometimes with a greenish covering of algae; with a thin crust, often cracked or furrowed when old, (Arora), up to 15cm x 23cm x 45cm, hoof-shaped to columnar, without stem, consistency becoming chalky, margin rounded; upper surface chalky white or discoloring to tan, not zoned, margin the same color; upper surface bald, often grooved, becoming cracked, (Gilbertson)
Flesh: thick, cheesy when young but chalky or crumbly when mature or old; white, (Arora), up to 10cm thick, cheesy when fresh, chalky and crumbly when dry; chalky white, not zoned, (Gilbertson)
Pores: 3-4 per mm, white or whitish, discoloring when old or dry; tube layers each 0.3-2cm thick, often stratified, (Arora), typically 4-5 per mm, but up to 1mm in some specimens, circular to angular, with thick entire walls that become torn when old; white to tan; usually rough; tube layers each up to 1cm thick, indistinctly stratified, colored as flesh or pale brownish, (Gilbertson)
Odor: farinaceous (Arora)
Taste: extremely bitter (Gilbertson)
Microscopic: spores 4-5.5 x 3-4 microns, broadly elliptic, smooth, (Arora), spores 6-9 x 3-4 microns, cylindric-elliptic to short-cylindric, smooth, inamyloid, colorless; basidia 4-spored, 20-25 x 6-8 microns, clavate, with basal clamp connection; cystidia none; hyphal system dimitic: context generative hyphae 2.5-7 microns wide, thin-walled, colorless, rarely branched, with clamp connections, lactiferous or gloeoplerous hyphae also abundant, up to 13 microns wide, thin-walled, "some with simple septa, often sinuous or branching, staining strongly in cotton blue", "sclerids also present in context, these contorted and irregularly shaped, often lobed, thick-walled, hyaline, walls up to 9 microns thick", trama generative and skeletal hyphae similar to those in context [context skeletal hyphae not described, but illustrated as thick-walled, nonseptate, and in one case branching], (Gilbertson)
Spore Deposit: whitish (Arora)
Habitat / Range
perennial, single or several on living or dead conifers, (Arora), single on living conifers, continuing decay and fruiting on dead trees and stumps, especially on old growth western larch and Douglas-fir, but also on Pinus (pine), Picea (spruce), Abies (fir), and Tsuga (hemlock), causing brown cubical heartrot of living conifers, commonly called brown trunk rot, thick white mycelial felts develop in shrinkage cracks, (Gilbertson)
