Ochrolechia frigida is characterised by a
thallus (the main body of the lichen) that is white to very pale grey in colour, often with a yellowish tinge. The thallus initially forms as a very thin warted crust that quickly develops distinctive small, smooth, spine- or -like extensions reaching up to 1.5 mm in length. These extensions eventually become (coral-like) in appearance. The lichen frequently forms extensive crusts that grow over low vegetation, other lichens,
mosses, and
plant stems.
Apothecia (fruiting bodies) are rarely produced in this species. When present, they measure up to 5 mm in diameter, occasionally reaching 7 mm, and are (attached directly to the thallus without a stalk). The of the apothecium is concave to flat in shape, pale brown or red-brown in colour, and lacks (a powdery or waxy coating). The (the rim around the disc containing algal cells) is relatively thin, smooth, and entire (without breaks or divisions). The (sexual spores produced in asci) measure 25–40 by 15–26
micrometres. Chemical
spot tests show that the thallus is C+ (red), KC+ (red), K–, Pd–, and UV–. These reactions indicate the presence of
gyrophoric acid and sometimes
lecanoric acid. ==Habitat, distribution, and ecology==