Dryopteris expansa

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

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

Discussion

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

None.

Lower Taxa