Horizontal stems on substrate surface, 1.3--2.7 mm wide; leaves appressed to ascending, linear to narrowly lanceolate, 1.8--4.5 X 0.6--1.2 mm, apex acute, scarious, often lost. Upright shoots 15--50 cm, branching regularly successively to 3 times; leaves appressed with decurrent base, subulate, 1.8--3.5 X 0.6--1 mm, apex acute. Branchlets flat in cross section, narrowly bladelike, 2.8--3.9 mm wide, annual bud constrictions very rare; underside dull, pale, flat; upperside green, flat, shiny. Leaves of branchlets 4-ranked; upperside leaves appressed, linear-lanceolate, free portion of blade 0.7--1.5 X 0.5--0.9 mm; lateral leaves appressed to spreading (spreading especially in juvenile stages), 3.1--5.5 X 1--2 mm; underside leaves very weakly developed, spreading, narrowly deltate, 0.3--1 X 0.3--0.7 mm, apex pointed. Peduncles mostly 2, 4.4--12.5 X 0.1--1.3 cm; leaves usually somewhat whorled, linear-lanceolate to nearly filiform, 2--3.3 X 0.5--0.9 mm, apex blunt to acute. Stalks mostly pseudowhorled, 2-forked, forks basal. Strobili 2--4 per upright shoot, 14--40 X 2--3 mm exclusive of elongate sterile tip; sterile tips to 11 mm (occurring on ca. 50% of specimens), apex blunt to acute if sterile tip is absent. Sporophylls deltate, 1.7--2.6 X 1.8--2.8 mm, apex abruptly tapering. 2 n = 46. Coniferous and hardwood forests and second growth, shrubby or open fields; 0--1500 m; St. Pierre and Miquelon; N.B., Nfld., N.S., Ont., P.E.I., Que.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Va., W.Va., Wis. An endemic in eastern North America, Diphasiastrum digitatum is the most abundant species of Diphasiastrum on the continent, much used for decoration as wreaths. It was long confused with the circumboreal D . complanatum .
Horizontal stems surficial or nearly so; erect stems more regularly branched, the branches determinate, without annual constrictions, the branch- systems flattened and fan-shaped; cones 2-4+ cm, commonly (not always) with a slender sterile tip several mm, the typically 4 peduncles tending to be subumbellately clustered; otherwise much like no. 16 [Lycopodium complanatum L.]; 2n=46. Dry open woods or meadows; Nf. and Que. to Man. and Minn., s. to Ga., Tenn., and La. (L. dillenianum; L. flabelliforme; L. complanatum var. f.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.