Capsules mature fall. Soil, sandstone, calcareous rock, bluffs, boulders, under overhanging ledges, seepage areas, logs; low to high elevations (0-2300 m); B.C., N.B., N.W.T., Ont.; Ala., Alaska, Ariz., Ark., Calif., Colo., Iowa, Ky., Maine, Md., Mass., Mich., Mo., Mont., N.H., N.Y., N.C., Ohio, Pa., Tenn., Tex., Vt., Va., Wash., W.Va.; Mexico; West Indies; Central America; South America; Arctic; Eurasia; Africa; Indian Ocean Islands; Pacific Islands (Hawaii, New Zealand); Australia.
H. A. Crum and L. E. Anderson (1958) detailed the abundant variation between specimens with very narrow, often fragile (W. C. Steere 1978) leaves and those with comparatively broad leaves, the latter commonly identified in herbaria as var. holtii (Braithwaite) Dixon. Variety tenuirostre often has a thin line of hyaline cells running up each leaf margin from the differentiated proximal cells, but this is largely of a single row of cells rather than a distinctly tapering broad wing of a V. Although the Mexican type of Trichostomum mollissimum (Brotherus) H. A. Crum is Pseudosymblepharis schimperiana (Paris) H. A. Crum with typical bushy, crowded linear-lanceolate leaves, specimens from the range of the flora previously identified under the former name are T. tenuirostre. Trichostomum tenuirostre, T. spirale, and T. recurvifolium share a similar areolation by the leaves with a band of rather thick-walled rectangular cells between the thinner walled basal cells and the distal medial cells.
Stem: rounded-pentagonal in section. Leaves: flattened, lanceolate, distal margins plane, entire or weakly toothed, not bordered; apex acute, plane or keeled; basal cells differentiated across leaf base as a U or V, commonly running up margins, not distinctly enlarged submarginally; distal laminal cells pluripapillose with low papillae; mucro conic, of 3–6 cells. Sexual: condition dioicous. Peristome: teeth bluntly lanceolate. Widely distributed in temperate and high-elevation tropical areas of the world, ranging into the Arctic.
Varieties 2 (2 in the flora). 1. Gemmae absent 3a. Trichostomum tenuirostre var. tenuirostre 1. Multicellular gemmae on rhizoids from adaxial surface of the costa or in soil 3b. Trichostomum tenuirostre var. gemmiparum.