Athyrium distentifolium var. americanum
American alpine lady fern
(c) J Straka, some rights reserved (CC BY), uploaded by J Straka · licence
Family: Athyriaceae · Type: Perennial · Native
Athyrium distentifolium var. americanum (American alpine lady fern) is a native California perennial in the Athyriaceae family, recognized by . Key differences: habitat (alpine rocky vs woodland streams), blade division (2-3-pinnate vs 1-2-pinnate-pinnatifid), elevation range.
American alpine lady fern is a native perennial found in the Klamath Ranges, California High Cascade Range, Sierra Nevada, Warner Mountains, and White and Inyo Mountains in moist or wet rock crevices, talus, cliffs, boulder bases, and streamsides at elevations of 1,700 to 3,700 meters. While not producing flowers, this delicate fern is characterized by its distinctive leaf structure. Growing with narrow, elegant fronds that can reach substantial heights, the fern develops complex multilayered leaves with intricate pinnate divisions. Its leaf blades are narrow-elliptic or lanceolate, intricately divided into 2 to 3 pinnate layers, with lower pinnae pairs slightly shorter than those above and ultimate segments showing shallow to deep pinnate lobing. The fern's midribs are notably glabrous or sparsely scaled, creating a refined and delicate botanical texture.
Identification and appearance
Key characters: 1 sympatric species. Key differences: habitat (alpine rocky vs woodland streams), blade division (2-3-pinnate vs 1-2-pinnate-pinnatifid), elevation range
Habitat and range
Habitat: Moist or wet rock crevices, talus, cliffs, boulder bases, streamsides
Elevation: 1700-3700 m
California counties: Mono, Tulare, Butte, Sierra, Nevada, Siskiyou, Tehama, Inyo, Alpine, Tuolumne, El Dorado, Shasta, Mariposa, Madera, Placer, Fresno, Plumas, Modoc, Trinity, Del Norte
Outside California: to Alaska, western Canada, Montana, Colorado, also eastern Can, Greenland, eastern Asia
How to tell it apart
vs Dryopteris: Athyrium has elongated or J-shaped spore covers; Dryopteris has round, kidney-shaped covers.; vs Pteridium: Athyrium grows in clumps; Pteridium spreads aggressively by underground runners forming large patches.; vs Woodwardia: Athyrium has scattered individual spore clusters; Woodwardia has chain-like rows of spore cases along veins.; vs Cystopteris: Athyrium is large (1-5 feet) with thick stems; Cystopteris is delicate and under 1 foot with hair-thin stems.; vs Dennstaedtia: Athyrium spore covers are on the vein; Dennstaedtia spore covers form cups at leaflet margins.
Frequently asked questions
Is Athyrium distentifolium var. americanum native to California?
Yes. Athyrium distentifolium var. americanum is native to California (recorded as native).
Where in California does Athyrium distentifolium var. americanum grow?
Athyrium distentifolium var. americanum occurs in Mono, Tulare, Butte, Sierra, Nevada, Siskiyou, Tehama, Inyo and other counties, at elevations of 1700-3700 m.
What plant family does Athyrium distentifolium var. americanum belong to?
Athyrium distentifolium var. americanum is in the Athyriaceae family, genus Athyrium.
What habitat does Athyrium distentifolium var. americanum grow in?
Athyrium distentifolium var. americanum grows in Moist or wet rock crevices, talus, cliffs, boulder bases, streamsides.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-09-30
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.