Osmunda cinnamomea L.
Cinnamon ferns are natives of the Americas, as well as eastern Asia. They date all the way back to the Paleozoic era, somewhere between 500 million and 250 million years ago—they may be the oldest living species. Their longevity is due in part to their prodigious production of spores, estimated at somewhere between 8 and 43 million per plant. Until 2008, these ferns were known as Osmunda cinnamomea.
Identification: Cinnamon ferns produce sterile fronds 12-59" (30-150 cm) tall and 6-8" (15-20 cm) wide, with opposing leaflets 1¾-4" (5-10 cm) long and ¾-⅞" (2-2.5 cm) wide. The leaflets are so deeply lobed that the fronds appear to be bipinnate. These ferns also produce separate fertile fronds 8-18" (20-45 cm) tall, and it is the light brown color of these fronds that give the fern its common name. As the plant ages, the fronds darken to brown and almost black. These ferns reproduce by spores as mentioned above, and also by cloning themselves, forming huge clonal groups.
Osmunda cinnamomea at Illinois Wildflowers
Osmunda cinnamomea on the Connecticut Botanical Society's Connecticut wildflowers site
Osmunda cinnamomea on the USDA Forest Service's Fire Effects Information Database
Osmunda cinnamomea on Wikipedia
Osmunda cinnamomea on nametheplant.net (Native & Naturalized Plants of the Carolinas and Georgia)
Cobb, Boughton, Farnsworth, Elizabeth & Lowe, Cheryl, Peterson Field Guides: A Field Guide to Ferns and Their Related Families of Northwestern and Central North America, Houghton Mifflin Company, 2005, p. 170
Osmunda cinnamomea description by Thomas H. Kent, last updated 25 Oct 2018.