Sp. Pl. 2: 1101. 1753.
Horizontal stems on substrate surface. Upright shoots clustered, 0.6–1.2 cm diam., dominant main shoot with 3–6 branches mostly in lower 1/2. Lateral branchlets few and like upright shoots; annual bud constrictions abrupt, branchlets mostly spreading. Leaves spreading, often somewhat ascending in distal 1/3 of branches, medium green, linear, 4–6 × 0.4–0.8 mm; margins entire; apex with narrow hair tip 2.5–4 mm. Peduncles 3.5–12.5 cm, with remote pseudowhorls of appressed leaves, loosely branched into 2–5 alternate stalks, 0.5–0.8 cm. Strobili 2–5 on alternate stalks (if double, usually with stalks 5–8 mm), 15–25 × 3–6 mm. Sporophylls 1.5–2.5 mm, apex abruptly reduced to hair tip. 2n = 68.
Habitat: Fields and woods
Elevation: 100–1800 m
St. Pierre and Miquelon, B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Sask., Alaska, Calif., Conn., Ga., Idaho, Ill., Ind., Ky., Maine, Md., Mass., Mich., Minn., Mont., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., Tenn., Vt., Va., Wash., W.Va., Wis., Mexico, West Indies, Central America, South America, Europe, Asia, Africa, Pacific Islands.
Plants found in eastern North America have been called Lycopodium clavatum var. clavatum; those in the western part of the range, which have been called L. clavatum var. integrifolium Goldie, are distinguished by early shedding of the characteristic hairs on the leaf tips.