Cinnamomea means cinnamon color.
Rhizome: erect, massive, forming a trunk, occasionally branching, hairs and old stipe bases woven together with black, fibrous roots.
Frond: 110 cm high by 30 cm wide, deciduous, dimorphic, outer ring of fronds longer, arching, sterile, inner fronds erect, fertile, earlier, blade/stipe ratio: 3:1 for sterile fronds.
Stipe: stipules (flared leaf base), unique to the family/genus, rusty wooly hairs when young, soon glabrous, vascular bundles: 1 in a U-shape where the top of the arms continue to curl.
Blade: 1-pinnate-pinnatifid, sterile fronds elliptic to oblong, arching, pinnae broadly oblong; fertile fronds with pinnae pairs greatly constricted, bearing sporangia, withering soon, somewhat waxy, shedding water, tuft of reddish hairs at the pinna base persistent for a while, rusty wool on pinnae and rachis soon falling.
Pinnae: 20 to 25 pair, catadromous, rotated to the horizontal; pinnules oblong, obtuse; costae costaee and rachis shallowly grooved above; margins entire; veins free, forked.
Sori: none, indusium: absent, sporangia: large, globose, greenish young, tan or black when mature, spores green, maturity: mid to late spring.
Habitat: stream banks, bog, swamps, acidic habitats.
Distribution: eastern North America and eastern Asia.
Hardy to -35°C, USDA Zone 3.
The tuft of hairs at the base of the sterile pinnae distinguishes this fern from O. claytoniana when fertile fronds are absent.
Osmundastrum cinnamomeum (L.) C. Presl see notes
Osmunda cinnamomea L. var. fokiensis Copel.
Osmundastrum cinnamomeum (L.) C. Presl var. fokiense (Copel.) Tagawa
Osmunda cinnamomea L. var. asiatica Fernald
Osmunda asiatica (Fernald) Ohwi