Postia fragilis

Scientific name:  Postia fragilis (Fr.) Julich  
Derivation of name: Postia means ???; fragilis
means "brittle, fragile, easily broken" perhaps in reference
to the quick bruising reaction upon handling.
Synonymy:   Polyporus fragilis Fr.; Tyromyces fragilis
(Fr.) Donk; Oligoporus fragilis (Fr.) Gilbn. & Ryvarden
Common names:   Brown-staining cheese polypore;
Staining cheese polypore.
Phylum:   Basidiomycota
Order:   Polyporales
Family:   Polyporaceae
Occurrence on wood substrate:  Saprobic; solitary or
overlapping clusters or in laterally fused rows on decaying
conifer wood; September through November. 
Dimensions:  Caps 1-10 cm wide.   
Upper surface:  White to yellowish to orange-brown,
staining reddish-brown when bruised; finely hairy to
Pore surface: White, staining yellowish, then reddish-
brown where bruised; pores 2-4 per mm..
Edibility: Inedible.
Comments: Specimens are soft when fresh and much
harder in age. The reddish-brown staining reaction is very

More information at

Figure 1. Postia fragilis on wood. The fruitbodies
show some of the reddish-brown staining characteristic of
this species. Photo ©Willaim Roody

Figure 2. Specimens on a log. Photo © Gary Emberger.

Figure 3. A closer look at some of the specimens in Figure 2.
Photo © Gary Emberger.

Figure 4. These are the same specimens as in Figure 3 but
photographed after sitting around on a collection table for
awhile. Note the great extent of staining from the repeated
handling. Photo © Gary Emberger.

Figure 5. Reddish-brown stained pore surface. Photo © Gary


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