Dryopteris expansa

(C. Presl) Fraser Jenkins & Jermy

Brit. Fern Gaz. 11: 338. 1977.

Common names: Northern wood fern spreading wood fern dryoptère dressée
Basionym: Nephrodium expansum C. Presl Reliq. Haenk. 1: 38. 1825
Synonyms: Dryopteris assimilis S. Walker Dryopteris dilatata subsp. americana (Fischer) Hultén
Treatment appears in FNA Volume 2.

Leaves monomorphic, tardily dying back in winter, to 90 × 30 cm. Petiole 1/3 length of leaf, scaly at least at base; scales scattered, brown with dark brown stripe. Blade green, deltate-ovate, 3-pinnate-pinnatifid, herbaceous, usually not glandular, occasionally finely and densely glandular. Pinnae ± in plane of blade, lanceolate-oblong; basal pinnae deltate, slightly reduced, basal pinnules equal to or longer than adjacent pinnules, basal basiscopic pinnule longer than basal acroscopic pinnule; pinnule margins serrate. Sori midway between midvein and margin of segments. Indusia lacking glands or sparsely glandular. 2n = 82.

Habitat: Cool moist woods and rocky slopes
Elevation: 50–1500 m


V2 405-distribution-map.gif

Greenland, Alta., B.C., Nfld. and Labr. (Nfld.), N.W.T., Ont., Que., Yukon, Alaska, Calif., Idaho, Mich., Minn., Mont., Oreg., Wash., Wis., Wyo., Europe.


Dryopteris expansa is diploid and is one of the parents of D. campyloptera. Where their ranges overlap in eastern Canada, these two species are very difficult to distinguish except by chromosome number. The growth habit (D. expansa leaves are more erect) is useful in the field. Three hybrids involving D. expansa are known; all are very rare.

Selected References


Lower Taxa

... more about "Dryopteris expansa"
James D. Montgomery +  and Warren H. Wagner Jr. +
(C. Presl) Fraser Jenkins & Jermy +
Nephrodium expansum +
Northern wood fern +, spreading wood fern +  and dryoptère dressée +
Greenland +, Alta. +, B.C. +, Nfld. and Labr. (Nfld.) +, N.W.T. +, Ont. +, Que. +, Yukon +, Alaska +, Calif. +, Idaho +, Mich. +, Minn. +, Mont. +, Oreg. +, Wash. +, Wis. +, Wyo. +  and Europe. +
50–1500 m +
Cool moist woods and rocky slopes +
Brit. Fern Gaz. +
Dryopteris assimilis +  and Dryopteris dilatata subsp. americana +
Dryopteris expansa +
Dryopteris +
species +