Plants 0.5--2.3 cm. Stem leaves loosely erect-appressed and ± loosely twisted when dry; elongate- to ovate-lanceolate, 2--3.5 mm, sharply acute, sometimes acuminate, cuspidate or apiculate; margins revolute to below apex, entire; distal laminal cells 9--14 µm wide, 1-stratose, with 2--3 large, conical or forked papillae per cell; basal laminal cells long-rectangular to rectangular, sometimes nodose at insertion. Sexual condition goniautoicous. Seta less than 1.4 mm. Capsule 1/2--3/4 emergent, sometimes almost exserted; urn oblong-ovate when mature, oblong to short-cylindric when old and dry, less than 1.4 mm, strongly 8-ribbed 2/3 to the entire length; stomates immersed, just below middle of the capsule, ± 1/2 covered by well-differentiated subsidiary cells; peristome double; endostome segments 8 or 16, of 1 or 2 rows of cells, smooth or finely roughened; exostome teeth 8, reflexed, densely and evenly papillose. Calyptra oblong, ± hairy, hairs with large, distinct papillae. Spores 10--15 µm.

Rocks and trees, at the bases of trees and in moist crevices of large boulders, especially common in moist, pine and deciduous forests; 2100--3000 m; Greenland; Alta., B.C., Nfld., Ont., Yukon; Ariz., Calif., Colo., Idaho, Mich., Mont., Nev., N.Mex., Oreg., S.Dak., Utah, Wash., Wyo.; Europe; Asia; Pacific Islands (New Zealand).

Orthotrichum alpestre is distinguished by the highly papillose distal leaf cells, slightly twisted leaves, which are always sharply pointed, a calyptra with papillose hairs, the absence of a preperistome, and the papillose or papillose-reticulate exostome. The endostome is always present in mature capsule and because of the enlarged crosswalls has a shiny appearance. The capsule, as it is usually seen, is oblong and strangulate, although the shape depends on age, and in some specimens the capsule is short-cylindric and not much constricted under the mouth.