Shoots erect, indeterminate, 8--12 cm, becoming short-decumbent; leaves of mature portion slightly smaller than leaves of juvenile portion (more pronounced in sun form); indistinct annual constrictions present (more pronounced in shade form); juvenile growth erect. Leaves spreading-ascending (shade) to appressed-ascending (sun) in mature portion, more reflexed in juvenile portion, green (shade) to yellow-green (sun), lustrous; largest leaves triangular, widest at base, 4--7.5 mm; smallest leaves lanceolate, 3.5--5 mm; margins almost entire, papillate; stomates on both surfaces, numerous on adaxial surface, 30--90 per 1/2 leaf. Gemmiferous branchlets produced in 1 pseudowhorl at end of annual growth; gemmae 4--5 X 3--4.5 mm, lateral leaves 1.5--2 mm wide, broadly acute. Spores 29--37 µm. 2 n = 268.

Terrestrial in sandy borrow pits, ditches, lakeshore swales, and conifer swamps, rarely on acidic, igneous rock or calcareous coast cliffs; 0--700 m, rarely to 1600 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Conn., Maine, Mass., Mich., Minn., N.H., N.Y., Ohio, R.I., Vt., Wis.; Europe; Asia.

Plants from Greenland formerly identified as Huperzia selago are H . appalachiana .