Plants 3--10 mm. Stem leaves stiffly erect-appressed, tips incurved when dry, spreading to wide spreading in distal portions of branches, ranging from ligulate to lanceolate-oblong, 1.3--2.6 mm, polymorphic, obtuse to broadly acute, rarely ending in short, hyaline cell, apiculate, or serrulate, concave; margins revolute to below apex or sometimes broadly reflexed in distal 1/2 of leaf, entire; distal laminal cells 8--13 µm wide, 1-stratose, with 2--3 conical papillae per cell; basal laminal cells broadly-rectangular, non-nodose. Sexual condition usually cladautoicous, rarely goniautoicous. Seta less than 2 mm. Capsule 2/3 emergent to shortly-exserted; urn cylindric to cylindric-elliptic when mature, 1.3--2 mm, strongly 8-ribbed entire length; stomates immersed in proximal 1/3 of capsule, ± completely covered by projecting subsidiary cells; peristome double; endostome segments 8, rarely 16, finely papillose, exostome teeth 8, rarely split to 16 when old, erect when mature, reflexed when old. Calyptra conic-oblong, naked or sparsely hairy, the hairs sometimes papillose because of projecting walls. Spores 11--18 µm.

Trunks of deciduous trees in dry, open areas, rarely on rocks; restricted to lower elevations; 100--2000 m; B.C.; Calif., Nev., Wash.; Europe, n Africa; Atlantic Islands (Azores, Canary Islands).

Orthotrichum tenellum is the only western species with deeply immersed stomates, blunt leaves, and oblong-cylindric capsules. Its small size distinguishes it from other Californian species found on trees.