Intermedia, presumably intermediate between D. carthusiana and D. campyloptera.
Rhizome: erect, stout.
Frond: 70 cm high by 20 cm wide, evergreen, monomorphic, blade/stipe ratio: 2:1 to 3:1.
Stipe: grooved, green, scattered, tan scales, more towards the base, vascular bundles: 5 in an arc.
Blade: 3-pinnate at the base, gradually less above, ovate, herbaceous, glandular.
Pinnae: 12 to 14 pair, anadromous on the lowest pinna pair, ± opposite pinnules above, lanceolate-oblong and more-or-less in plane of blade; lowest pair lanceolate, and not reduced in size; pinnules inner, lower pinnule on the lowest pinna somewhat shorter than the next one; costae grooved above, continuous from rachis to costae; margins serrate, spiny; veins free, forked.
Sori: round, in 1 row between midrib and margin, indusium: reniform, at a sinus, sporangia: brown, maturity: midsummer.
Habitat: moist, rich woods, especially in limestone areas.
Distribution: northeastern North America.
Hardy to -35°C, USDA Zone 3.
Distinguished from the other spinulose wood ferns by the first lower
pinnules of the lowest pinnae the same length or shorter than the
Aspidium intermedium Muhlenberg ex Willdenow
Dryopteris austriaca (Jacquin) Woynar var. intermedia (Muhlenberg ex Willdenow) C. V. Morton
Dryopteris spinulosa (O. F. Mueller) Watt var. intermedia (Muhlenberg ex Willdenow) L. Underwood
Illustration by Edgar Paulton, from How to Know the Ferns and Fern Allies, John T. Mickel, © 1979 Wm. C. Brown Co.