Synonyms & Characteristics for Year-round Identification of Dryopteris - R. Parker

Each fern frond is made up of the stipe (lower ‘stem’) and blade (with the ‘leafy parts’). The blade has a rachis (‘stem’) and, if divided, pinnae. Each pinna can be further divided into pinnules (twice divided), each of which could even be further divided (thrice-divided). Indusia cover the sori which contain the spores.

All four Dryopteris species below have brown-to-golden scales on the rachis and stipe, especially at the base, clustered fronds up to 30" long. D. intermedia can be 8" wide, D. marginalis & D. carthusiana up to 10 inches, D. campyloptera up to 12" wide. The sori are round with kidney shaped indusia.

Dryopteris intermedia

Synonyms (ref 3,9): Aspidium intermedium, Dryopteris austriaca var. intermedia, Dryopteris spinulosa var. intermedia, American or intermediate shield or wood fern. (Compare w/ D. carthusiana, below.) Fronds evergreen, oblong-lanceolate (almost triangular), twice-thrice divided, toothed, very lacy. Lower half of basal pinnae almost always have second pinnule elongated compared to first pinnule. Sori are small, round, evenly spaced along midrib of pinnules.

Dryopteris marginalis

Synonyms (ref 3,9): Aspidium marginale, Polypodium marginale, Aspidium filix-mas var. marginale, Filix-Mas marginalis, Lastrea marginalis, Nephrodium marginale, Polystichum marginale, Thelypteris marginalis, evergreen or leather wood fern, marginal shield fern. Fronds evergreen, lanceolate (longest pinna fifth from base), dark blue-green (lighter in spring), heavily veined, leathery texture, twice divided, not toothed. Sori very large, almost on margin of pinnules. Indusia attached at center looks like short-stemmed mushroom. Basal scales long and dense.

Dryopteris carthusiana (& D. campyloptera)

Synonyms (ref 3, 9): D. spinulosa, Aspidium spinulosum, Polypodium carthusianum, Dryopteris austriaca var. spinulosa, Polypodium spinulosum, Polystichum spinulosum, Thelypteris spinulosa, toothed wood fern, spinulose shield fern. Fronds deciduous, oblong-lanceolate (longest pinna roughly center of blade), twice-thrice divided, toothed. Smooth rachis. Lower half of basal pinnae has elongated first pinnule compared to the second pinnule. Pinnules usually angled "up" toward tip (vs. D. campyloptera which is also deciduous but has wider blades and pinnules almost straight out from stem). Sori small, situated on veins near pinnule midrib. Reported to occasionally have some green leaves remaining through very mild falls & winters.


"Dryopteris intermedia and the other taxa in the 'D . spinulosa complex' have long confounded taxonomists. Dryopteris intermedia is diploid and is one of the parents of the allotetraploids D . carthusiana and D. campyloptera. Dryopteris intermedia hybridizes with eight species. All hybrids are easily detected by the distinctive glandular hairs on the indusia and, usually, on the costae and costules." (reference 10)

"Even though (D. marginalis) hybridizes with 10 other species, and some of these hybrids are fairly common, D. marginalis is not known to be involved in the formation of any fertile polyploid. Hybrids can be detected by malformed spores and the nearly marginal sorus position." (reference 10) 


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• 2. New York Natural Heritage Program, NY State DEC.
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