Plants robust. Leaves 3-8(-12) mm, 0.8-1.1 mm wide at mid-limb; cells of mid-limb lamina (8-)9-16(-18) × (8-)9-14 µm; costa ending below apex, papillose on abaxial surface of sheath and limb; base of costa dark and swollen, more strongly attached to stem than is the lamina; with distal leaves often larger and deciduous, but never with loose clusters of linear leaves at stem tips.

Sporophytes extremely rare. Wet calcareous sites such as seepage slopes, moist crevices or cliff ledges, snow patches, edges of small creeks and ponds in Arctic-montane areas, often intermixed with other mosses, including Timmia sibirica, T. norvegica var. excurrens, and T. austriaca; low to high elevations (0-3600 m); Greenland; Alta., B.C., Man., Nfld. and Labr. (Nfld.), N.W.T., Nunavut, Que., Yukon; Alaska, Colo., Mont.; Eurasia (Alps, Russia, Scandinavia, United Kingdom); Atlantic Islands (Iceland); Pacific Islands (New Zealand).

Only three sporulating specimens of var. norvegica are known (one from Alaska). The deciduous leaves undoubtedly act as vegetative propagules.