Stems slender, short-creeping or ascending, not climbing. Leaves dimorphic, cespitose, erect or spreading, fertile leaves more erect and longer than sterile leaves. Petioles of fertile leaves reddish brown to purple-black, 15-60 cm, coarsely scaly proximally. Petioles of sterile leaves reddish brown, 2-30 cm, coarsely scaly proximally. Fertile blades erect, narrowly rhombic, 1-pinnate, without conform terminal pinna, 25-65 × 3-15 cm, glabrous. Sterile blades spreading, narrowly oblanceolate to linear-lanceolate, pinnatifid to apex and so without conform terminal pinna, 20-75 × 3-14 cm, tapering at base, glabrous. Rachises of fertile and sterile leaves with indument of filiform, spreading scales abaxially. Fertile pinnae not articulate to rachis, sessile, decurrent and surcurrent to rachis; larger pinnae slightly curved, linear, 25-32 × 1.5-2 mm; margins entire, slightly to moderately revolute; costae with indument of a few small scales abaxially, often concealed by sori. Sterile pinnae closely spaced, not articulate to rachis, base fully adnate; larger pinnae curved, linear to oblong-linear or barely wider beyond middle, 15-35 × 3.5-5 mm; margins entire. 2 n = 68. Wet coniferous woods and swamps; 0-1400 m; B.C.; Alaska, Calif., Idaho, Oreg., Wash. Blechnum spicant is found primarily along the coast and in coastal mountain ranges.