Horizontal stems on substrate surface. Upright shoots clustered, shoots 0.5--0.8 cm diam., dominant main shoot branches 2--3(--4), mostly in lower 1/2. Lateral branchlets few and like upright shoots; annual bud constrictions abrupt and conspicuous, shoots 0.5--0.8 cm wide, branches mostly erect. Leaves ascending to appressed, medium green, 3--5 X 0.4--0.7 mm; margins entire; apex with narrow hair tip 1--3 mm. Peduncles 3.5--12.5 cm, with remote pseudowhorls of appressed leaves, unbranched. Strobili solitary (if double, usually nearly sessile), 20--55 X 3--5 mm. Sporophylls 1.5--2.5 mm, apex rather gradually reduced to hair tip. 2 n = 68.

More or less exposed, grassy fields and openings in second-growth woods; 50--1500 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Maine, Mich., Minn., N.H., N.Y., Vt., Wis.; Eurasia.

Lycopodium lagopus is generally more northern than its sister species, L . clavatum (W. J. Cody and D. M. Britton 1989). Where they come together, however, they can grow side by side (even in southern Michigan) and maintain their distinctions.