Plants green to yellowish green, becoming brown with age, dull, in loose to somewhat dense tufts. Stems 2-5 mm, simple or seldom branched, with a few dark red rhizoids near the base. Leaves erect-spreading, slightly crisped to falcate-secund when dry, 1-3 mm, lanceolate to linear-lanceolate, channelled, lamina 1-stratose except near margins; margins plane to narrowly recurved from just beyond the leaf base to mid leaf, serrate to strongly serrate from mid leaf to the acute apex, 2-stratose distally and rarely a cell inward; costa distinct, percurrent, occupying ¹/6-¹/3 width of the leaf base; lamina cells thick-walled, distal cells 8-24 × 8 µm, becoming slightly broader and longer in the base. Specialized asexual reproduction unknown. Sexual condition dioicous. Seta orange-yellow, brownish or reddish, 0.8-1.2 cm, erect. Capsule erect, yellow or light brown, curved and asymmetric, 1-2(-2.5) mm, often swollen at the base; operculum rostrate, 0.5-0.8 mm; peristome 200 µm, 2-fid, the filaments ± unequal, linear, somewhat twisted when dry, strongly papillose to spiculose. Spores round, 9-13 µm, appearing smooth to minutely papillose. Capsules mature spring (Jun). Primarily on serpentine soils, clearings along roads; moderate elevations (ca. 400 m); Md., N.H., Vt. Ditrichum tortuloides was synonymized by H. A. Crum and L. E. Anderson (1981) with D. ambiguum. However, R. R. Ireland and H. Robinson (2001) discussed reasons for distinguishing the two species. For a discussion of the similarities and distinguishing characteristics, see under 1. D. ambiguum.