Osmundastrum cinnamomeum

Osmundastrum cinnamomeum, commonly known as the cinnamon fern or the buckhorn fern, is a species of royal fern native to the Americas and Asia. It is the sole living representative of the genus Osmundastrum, which was separated from Osmunda after modern phylogenetic studies demonstrated that Osmunda was not monophyletic. In North America it occurs from southern Labrador west to Ontario, and south through the eastern United States to eastern Mexico and the West Indies; in South America it occurs west to Peru and south to Paraguay. In Asia it occurs from southeastern Siberia south through Japan, Korea, China and Taiwan to India, Myanmar, Thailand and Vietnam.

Osmundastrum cinnamomeum has a fossil record extending into the Late Cretaceous of North America, approximately 73 million years ago, making it one of the oldest living plant species. The genus itself goes back to the Triassic.

The cinnamon fern mainly inhabits swamps, bogs and moist woodlands. It also thrives in open meadows as a dominant species. The fern often grows in wet savannas, wetlands, floodplains, marshes, dry-mesic forests and subtropical prairies. The cinnamon fern is a highly successful species and can thrive in temperate, subtropical and tropical ecosystems.