The lichen forms a flat, leaf-like structure (thallus) that can grow up to 27 cm in diameter, typically appearing grey or brown and covered in fine hairs.

P. hirsuta grows mainly on trees in forested areas, particularly those dominated by southern beech (Nothofagus) species, but can also be found on rocks, soil, and stumps.

The species is widely distributed in Argentina and Chile, from central regions to Tierra del Fuego, and has been observed in various forest types and elevations.

Joseph Hooker in 1847 and briefly Nylander in 1860 considered it a synonym of Sticta obvoluta, primarily due to the presence of yellow pseudocyphellae.

Additionally, Franz Meyen and Julius von Flotow in 1843 erroneously listed an undescribed species, Sticta pilosa, as a synonym of S. hirsuta, further complicating its taxonomic history.

The margins of the lobes are mostly smooth, slightly sinuous or shallowly folded, and can occasionally bear small, leaf-like structures known as phyllidia.

The upper surface of the thallus is typically dull grey to bluish-grey when wet, and shifts to pale buff-grey, brown, or olive when dry.

[4] Pseudocyphellaria hirsuta does not produce soredia, isidia, or maculae, which are common reproductive or structural features in other lichen species.

It is typically covered in a soft, velvety layer of tomentum, a dense mat of fine hairs, which is whitish at the edges and browner towards the centre.

Scattered across this surface are small, yellow structures called pseudocyphellae, which are slightly sunken and appear as tiny warts without a defined border.

[4] The Chilean endemic Pseudocyphellaria dasyphyllidia shares similarities with P. hirsuta, but can be distinguished by its narrower, more finely divided lobes, true phyllidia on margins and surfaces, and generally smaller apothecia.

It produces smaller spores and is better adapted to drier, sunnier environments compared to P. hirsuta, which prefers humid, lower-altitude forests.

The species has a wide distribution within these countries, ranging from central Chile to Tierra del Fuego and Staten Island in Argentina.