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OSMUNDACEAE (Royal Fern Family)

References: Lellinger (1985); Whetstone & Atkinson in FNA (1993b).

A family of 3 genera and about 15-35 species.

Osmunda Linnaeus (Royal Fern, Cinnamon Fern, Interrupted Fern)

A genus of about 10 species, tropical and temperate.

1. Leaves bipinnate, each pinna fully divided into distinct pinnules, the larger pinnules 3-7 cm long and 0.7-2.0 cm wide; spores borne on modified pinnae in the terminal portion of the leaf blade; veins mostly 2-forked...... O. regalis var. spectabilis

1. Leaves pinnate-pinnatifid, each pinna pinnatifid but not divided into distinct pinnules; spores borne either on separate, modified, fertile leaves, or on modified pinnae in the middle of the leaf blade; veins mostly 1-forked......2

3. Leaf surfaces and upper portion of the rachis not glandular......O. cinnamomea var. cinnamomea

3. Leaf surfaces and upper portion of the rachis densely glandular pubescent......O. cinnamomea var. glandulosa


Osmunda cinnamomea Linnaeus var. cinnamomea, Cinnamon Fern. Cp, Pd, Mt (NC, SC, VA): bogs, peatlands, pocosins, wet savannas, floodplains, blackwater stream swamps; common. March-May. Ranging from Labrador west to MN, south to FL, TX, NM, Central America, and South America. Another variety occurs in e. Asia. Sterile plants are sometimes confused with Woodwardia virginica, which also has rather coarse, pinnate-pinnatifid leaves and grows in similar wet, acid places. Osmunda is much coarser, has cinnamon tufts of tomentum present in the axils of the pinnae (vs. absent), has the rachis greenish and rather fleshy in texture (vs. brown and wiry), and bears fronds clumped or tufted from a massive, woody, ascending rhizome covered with old stipe bases (vs. fronds borne scattered along a thick, horizontal, creeping rhizome). [= C, F, K; O. cinnamomea -- RAB, FNA, G, S, W, in part (infraspecific taxa not distinguished)]

Osmunda cinnamomea Linnaeus var. glandulosa Waters, Glandular Cinnamon Fern. Cp, Mt (VA): acidic seepage swamps, sphagnous seeps; rare (VA Rare List). March-May. This taxon is poorly understood, but appears to be worthy of taxonomic recognition. It is known from scattered locations in e. North America. [= F, K; O. cinnamomea -- FNA, in part (infraspecific taxa not distinguished)]

Osmunda claytoniana Linnaeus var. claytoniana, Interrupted Fern. Mt (NC, SC, VA), Pd (VA), Cp (VA): upland forests, woodlands, and balds, moist to rather dry; common (uncommon in Piedmont, rare in Coastal Plain). March-June. Ranging from Newfoundland west to MN, south to n. GA, TN, and AR; another variety occurs in e. and sc. Asia. [= C, F; O. claytoniana -- RAB, FNA, G, K, S, W, infraspecific taxa not distinguished]

Osmunda regalis Linnaeus var. spectabilis (Willdenow) A. Gray, Royal Fern. Cp, Mt, Pd (NC, SC, VA): bogs, marshes (including tidal), moist forests, floodplains, swamp forests; common. March-June. Ranging from Newfoundland west to Saskatchewan, south to FL, TX, and Mexico; var. regalis is widespread in Eurasia. [= RAB, C, F, FNA, G, K, W; O. regalis -- S, varieties not recognized]

The hybrid Osmunda Hruggii R. Tryon [O. claytoniana var. claytoniana H regalis var. spectabilis] is known from Giles County, VA and one other historic population in CT. It has 2-pinnate sterile leaves, with the pinnules sessile.


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Flora of the Carolinas and Virginia, Working Draft of 27 October 1997 -- KEY TO PTERIDOPHYTE GENERA. Alan S. Weakley. The Nature Conservancy, Southeast Regional Office, Southern Conservation Science Department.