Northern Ontario Plant Database

Plant Description

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Osmundastrum cinnamomeum (L.) C.Presl

En: cinnamon fern
Fr: osmonde cannelle

Osmundaceae (Flowering fern Family)

General: A large, perennial fern; fronds large and erect, growing from thick rhizomes. The sterile (1) and fertile (2) fronds are separate and differently shaped (dimorphic fern). The fertile fronds appearing before the sterile fronds, and shrivel soon after spores are shed.

Sterile Fronds: Oblong to oblanceolate, to 1.6 dm long, pinnate. Pinnae alternate to nearly opposite along the rachis, with each pinna deeply lobed (pinnatifid); each segment oblong, blunt, and with entire margins; veins forked (dichotomous). Stalk of the frond (stipe) and young fronds bearing cinnamon-brown hairs, which persist at the bases of the pinnae.

Fertile Fronds: Narrow, bladeless, erect, bipinnate, densely covered in woolly, cinnamon-brown hairs, bearing clusters of many small sporangia; indusia are lacking. Fertile fronds grow from the centre of the crown of fronds; they appear before, and are slightly shorter than, the sterile fronds.

Habitat and Range: Swamps, low wet woods, wet thickets. Cinnamon fern is native to eastern North America and eastern Asia. Its range extends westward around Lake Superior, but it is absent from other regions of northern and northwestern Ontario.

Similar Species: The cinnamon fern has sterile fronds that are similar to those of the interrupted fern, Osmunda claytoniana. But the interrupted fern can be distinguished by the several pairs of fertile pinnae situated in the middle of an otherwise sterile frond. These fertile pinnae shrivel and drop off after the spores are shed, leaving the frond with an obvious interruption between the sterile pinnae. Compare the webpages of Osmunda cinnamomea and Osmunda claytoniana from the Connecticut Ferns website, published by the Connecticut Botanical Society.

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