Flora of North America species comparison

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Dryopteris expansa

alpine buckler fern, dryoptère dressée, northern fern, northern wood fern, spiny wood fern, spreading wood fern
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.
Indusia

lacking glands or sparsely glandular.
Sori

midway between midvein and margin of segments.
2n

= 82.

Dryopteris expansa
Habitat Cool moist woods and rocky slopes
Elevation 50–1500 m (200–4900 ft)
Distribution
from FNA
AK; CA; ID; MI; MN; MT; OR; WA; WI; WY; AB; BC; NF; NT; ON; QC; YT; Greenland; Europe
[WildflowerSearch map]
[BONAP county map]
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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 2.
Parent taxa Dryopteridaceae > Dryopteris
Sibling taxa
D. arguta, D. campyloptera, D. carthusiana, D. celsa, D. cinnamomea, D. clintoniana, D. cristata, D. filix-mas, D. fragrans, D. goldieana, D. intermedia, D. ludoviciana, D. marginalis
Synonyms Nephrodium expansum, D. assimilis, D. dilatata subsp. americana
Name authority (C. Presl) Fraser Jenkins & Jermy: Brit. Fern Gaz. 11: 338. (1977)
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Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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