Plants in dense tufts, light green to yellowish, glossy. Stems to 8 cm, 1-1.5 mm wide across leafy stem, erect, julaceous. Leaves erect, closely imbricate, ovate or oblong-ovate, symmetric, con-cave, 1.5-2.5 × 0.8-1.2 mm; margins broadly recurved throughout, entire or denticulate at apex; apex acuminate, not abruptly contracted, ; costa with one branch sometimes reaching 1/3 leaf length; alar cells rectangular or inflated and oval, 40-60 × 9-24 µm, in 2-4 vertical rows, terminating in 1 cell at base, region triangular or rarely somewhat oval; medial laminal cells 85-141 × 6-12 µm. Specialized asexual reproduction unknown. Sexual condition unknown. Sporophytes unknown.

Swales, wet tundra, rocky slopes, cliffs; low to moderate elevations (0-1200 m); Greenland; N.W.T.; Alaska; n Europe (Norway).

Plagiothecium berggrenianum is an Arctic species that has been confused with P. cavifolium, or with julaceous forms of P. denticulatum and P. laetum. The acuminate leaves with recurved apices separate P. berggrenianum from P. denticulatum, while the inflated, oval cells in the decurrencies will distinguish it from P. cavifolium and P. laetum.