Leaves dimorphic, 45–100 × 12–20 cm; fertile leaves dying back in winter; sterile leaves 1–several, smaller, green through winter. Petiole 1/4–1/3 length of leaf, scaly at least at base; scales scattered, tan, sometimes with dark brown center. Blade green, lanceolate, with nearly parallel sides, pinnate-pinnatifid, herbaceous, not glandular. Pinnae of fertile leaves twisted out of plane of blade but not fully perpendicular to it, narrowly elongate-deltate; basal pinnae narrowly elongate-deltate, much reduced; basal pinnules longer than or equal to adjacent pinnules, basal basiscopic pinnule and basal acroscopic pinnule equal; pinnule margins serrate or biserrate, with spiny teeth. Sori midway between midvein and margin of segments. Indusia lacking glands. 2n = 246.
Habitat: Swampy woods
Elevation: 50–600 m
N.B., Ont., Que., Conn., Ind., Maine, Mass., Mich., N.H., N.J., N.Y., Ohio, Pa., R.I., Vt.
Dryopteris clintoniana is a North American endemic and an allohexaploid derived from D. cristata and D. goldieana. Dryopteris clintoniana hybridizes with six species. Hybrids can be identified by the fairly narrow blades and elongate-deltate proximal pinnae.