Plants medium to large and robust. Stems 5--10(--20) cm. Leaves 6--12 mm, subsquarrose and broadly spreading-recurved when moist; marginal lamina 2--5 cells wide, erect; lamellae 5--7 cells high, the marginal cells rounded and ± thick-walled. Sexual condition dioicous. Capsule short rectangular, yellowish to brownish; hypophysis cylindric, delimited by a shallow groove; peristome teeth 64, very regular in form.

Low to middle elevations, B.C., N.B., Ont., s Alaska, Wash.; Europe; sw Asia (Caucasus Mts., Turkey), s Russia (Altai Mts., n Africa (Algeria), Atlantic Islands (Iceland, Macaronesia).

Typical Polytrichastrum formosum is rare in N. Am., and its distribution and ecology poorly documented. It may possibly be an introduction, like Atrichum undulatum, another common European species believed to be introduced here. European treatments often compare P. formosum with Polytrichum commune, which scarcely describes our North American expression of the species. The habitat and ecology of the European plant is also distinct: A. J. E. Smith (2004) describes P. formosum in Britain as a common and weedy species of heaths, moorland, woods, outcrops, and old walls, from sea level to 500 m.