[8] The fruit bodies (basidiocarps) are pale, with a smooth greyish-brown top surface, while the creamy white underside has hundreds of pores that contain the spores.

These fungal "individuals" can sometimes be seen if a slice of brown-rotted birch wood is incubated in a plastic bag for several days.

In a large-scale study of over 2600 fruit bodies collected in eastern Canada, 257 species of arthropods, including 172 insects and 59 mites, were found.

[17] Old fruit bodies that have survived the winter are often colonized by the white to pale yellow fungus Hypocrea pulmonata.

[18] Fomitopsis betulina has been widely used in traditional medicines, and has been extensively researched for its phytochemistry and pharmacological activity.

[20] Agaric acid, found in the fruit body of the fungus, is poisonous to the parasitic whipworm Trichuris trichiura.

[21] The velvety cut surface of the fruit body was traditionally used as a strop for finishing the edges on razors,[15] and as a mounting material for insect collections.