Distribution: Widespread in western North America from Alaska to southern Mexico.
Habitat: Coniferous forests, wherever hosts are present: Abies, Sequoiadendron, Tsuga, Pseudotsuga, and Picea. Generally inside stumps, at the base of snags or on the undersides of logs.
Substrate: Coniferous wood.
Origin: Widespread in coniferous forests.
Conservation Status: Not of concern
Differs from Fomitopsis mounceae in thinner, rougher, sulcate cap, sharper margin, and never a red band. Differs from Heterobasidion irregulare primarily by host preference: H. irregulare is found on pines, junipers, and incense cedars.
PNW Herbaria: Specimen records of Heterobasidion occidentale in the Consortium of Pacific Northwest Herbaria database
CalPhotos: Heterobasidion occidentale photos