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. 2 n = 246.
Dryopteris clintoniana is a North American endemic and an allohexaploid derived from D . cristata and D . goldiana . Dryopteris clintoniana hybridizes with six species. Hybrids can be identified by the fairly narrow blades and elongate-deltate proximal pinnae.
Perennial fern 0.5 - 1.2 m tall Leaves: clustered, stalked, green, 30 - 90 cm long, 12 - 20 cm wide, in outline lance-shaped with nearly parallel sides, but pinnately compound. The leaves are typically hairless on the upper surface, never glandular-hairy, but the lower surface of the main "midrib" (rachis) has sparse scales, and a lengthwise groove along its upper surface. Fertile leaves die back in winter, but at least one sterile leaf remains green through winter. Rhizome: short-creeping to erect, scaly. Leaf stalks: one-third length of blade (up to 35 cm), with scattered, egg-shaped, about 1 cm long, tan (sometimes with dark brown center) scales at base. Spores: 64 per sac, brownish, all of one kind, single-sectioned (monolete), oblong or kidney-shaped, and coarsely wrinkled or with folded wings. The spores give rise to the gametophyte (the sexual phase of the plant), which is small, green, heart-shaped, hairless or often with glands or hairs, and sits above the ground.
Similar species: Dryopteris clintoniana is most similar to one of its parents, D. cristata, but that species differs by having wider basal leaf divisions (pinnae), the lowest pair of pinnae are usually under 5 cm long, and the pinnae of the fertile leaves are twisted at nearly a right angle (ninety degrees) to the main plane of the blade. Also incredibly similar is the other parent of this fertile hybrid species, D. goldiana, but that species can be distinguished by its more egg-shaped basal pinnae that are over 10 cm long, a very abruptly tapering leaf tip, and very dark brown (almost black), pale-edged scales at the base of the leaf stalk.
Habitat and ecology: Very rare, possibly extinct in Indiana, typically was found in our eastern most counties in wet thickets, low wet woods, and along swamp margins.
Occurence in the Chicago region: native
Notes: The Chicago Region is at the farthest west point of the range for this species. It is endemic to North America, and originated from hybridization of D. cristata and D. goldiana. Dryopteris clintoniana hybridizes with six other species, and those hybrids can usually be recognized by the fairly narrow leaf blades and more elongate-triangular lower pinnae.
Sterile and fertile lvs similar or only slightly different, evergreen, to 13 dm; petiole to 3.5 dm, scaly at the base, the scales ovate, ca 1 cm, concolorous or with darker brown center; blade lanceolate, commonly 1.5-2 dm wide, pinnate-pinnatifid, ±acuminate; pinnae mostly 10-18 pairs, the larger ones mostly 7-11 נ2-4 cm, short-petiolulate, lance-oblong, acuminate, the 10-15 pairs of segments oblong, 10-23 נ6-9 mm, obtuse, incurved-serrate or biserrate, the teeth subspinulose; veins 5-7 pairs per segment; basal pinnae relatively short and broad-based, mostly 1.5-2.5 times as long as wide; 2n=246, thought to be an alloploid of nos. 3 [Dryopteris cristata (L.) A. Gray] and 5 [Dryopteris goldiana (Hook.) A. Gray]. Swamps and wet woods; Me. and Que. to Wis., s. to N.Y., n. N.J., n. Pa., n. O., and n. Ind.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.