Plants: small to large, rusty green, golden green, yellow-green, or pale green. Stems: 1–8+ cm, pale to yellowish green, brown with age, creeping to erect, complanate-foliate or not, irregularly pinnate to nearly unbranched, attached shoots often regularly pinnate, branches 1–3 cm; hyalodermis absent, central strand poorly developed; pseudoparaphyllia filamentous, 1–3-seriate at base. Leaves: strongly imbricate, not to decidedly falcate-secund, ovate to oblong-lanceolate, gradually or abruptly narrowed to apex, 1.5–2 × 0.5–0.8 mm; base not decurrent, not auriculate; margins recurved to plane proximally, serrulate (sometimes weakly) distally, occasionally nearly entire; acumen slender; costa double and short or obscure; alar region well defined, basalmost cells larger, sometimes hyaline, yellowish or brownish; basal laminal cells shorter, wider than medial cells, not pigmented, walls not pitted; medial cells (50–)60–80 × 3–4(–5) µm. Sexual: condition dioicous; inner perichaetial leaves oblong-lanceolate, margins serrulate distally, costa obscure. Seta: reddish, 1–2.5(–3) cm. Capsule: slightly inclined, reddish, cylindric, 1.8–2.5(–2.8) mm; annulus 1–3-seriate; operculum conic to rostrate; endostome cilia 1–2(–3). Nearly worldwide, except Antarctica.

Varieties 9 (4 in the flora). Hypnum cupressiforme is an extremely polymorphic species, reflected in the more than 60 varieties that have been described. The species has a wide ecological amplitude as well as a nearly cosmopolitan distribution and is found in all climatic regions except the Antarctic. Taxonomic features reliable in most other species of Hypnum are plastic in H. cupressiforme. Within a single clone, it is possible to sort out several named varieties. Variety lacunosum Bridel was noted by H. Ando (1989) to be weakly differentiated in North America, and he tentatively cited specimens from Nova Scotia, Newfoundland, and South Dakota. Ando noted that var. lacunosum typically is robust, thick-complanate to julaceous, with leaves almost straight to weakly falcate and abruptly narrowed to a short acumen, but the North American material is not robust and is therefore problematic.

Plants: small to medium-sized, pale to dark green to golden brown. Stems: 1–3 cm, reclining to suberect, weakly complanate-foliate, pinnate to irregularly branched. Leaves: usually falcate, sometimes strongly so, long-ovate or ovate-lanceolate, gradually narrowed to apex; margins subentire to distinctly toothed distally; alar cells many and subquadrate or few and quadrate, not pigmented, region not excavate. Branch: leaves 1–2 × 0.2–0.6 mm, sometimes smaller or larger. Phenology: Capsules mature spring.

Terrestrial, epiphytic, rock. low to high elevations (0-4000 m). Greenland, Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon, Alaska, Ark., Colo., Conn., Del., Ill., Iowa, Maine, Md., Mass., Mich., Mont., N.Y., N.C., Pa., S.Dak., Tex., Vt., Wash., Wis., Mexico, South America, Eurasia, Africa, Atlantic Islands, Pacific Islands (New Zealand), Australia.

Variety cupressiforme accommodates specimens that cannot be placed in any of the nine varieties recognized by H. Ando, including those accepted here. Sporophytes are produced summer to fall.

Plants: small, pale green to dull green, sometimes yellowish. Stems: 2–6 cm, creeping, subjulaceous, irregularly branched to somewhat pinnate. Leaves: straight to somewhat falcate, oblong-lanceolate, gradually narrowed to apex; margins nearly entire; alar cells many, subquadrate; laminal cells 60–80 × 3–4 µm (or slightly larger). Branch: leaves 1–1.4 × 0.2–0.4 mm or slightly smaller. Phenology: Capsule maturity unknown.

Vertical surfaces of cliffs and tree trunks. low to high elevations (0-2500 m). N.B., N.S., P.E.I., Ark., Conn., Maine, Mass., Mich., N.H., N.J., N.Y., N.C., Okla., Pa., Tenn., Tex., Va., s South America, Europe, Asia, Africa, Pacific Islands (New Zealand), Australia.

When well-developed, var. filiforme is distinctive, with filiform julaceous stems and straight leaves. There are variants with somewhat falcate-secund leaves that can be confused with H. andoi. The latter species has long-attenuate leaf apices, is not julaceous, although filiform, and the leaves are not strongly imbricate as in var. filiforme. The many specimens that closely resemble var. filiforme strongly suggest that it may be an environmental form induced by the habitat that holds moisture rather briefly during the growing season.

Plants: medium-sized, yellowish green to brown. Stems: 5–8+ cm, creeping, subjulaceous to complanate-foliate, regularly to irregularly pinnate, to 2-pinnate. Leaves: straight to weakly falcate, sometimes homomallous, oblong-lanceolate, gradually narrowed to apex; margins subentire to weakly toothed; alar cells many, subquadrate, pigmented, region excavate. Branch: leaves 1.5–2 × 0.4–0.6 mm or slightly larger. Phenology: Capsule maturity unknown.

Terrestrial, cliff shelves, horizontal rock surfaces, exposed and sheltered sites, usually calcareous substrates. low to high elevations (0-4000 m). B.C., Yukon, Alaska, Colo., N.Mex., N.Dak., Europe, Asia, Pacific Islands (New Zealand).

Variety subjulaceum is frequent in the Alaskan Peninsula but uncommon (or unrecorded) elsewhere in North America; it is found mainly at high elevations in Europe. The variety has somewhat concave leaves. No sporophytes were found in North American material. The acutely attached branches, closely imbricate, straight leaves with sharp apices, and frequently excavate pigmented alar cells make this a distinctive variety.