Osmundastrum cinnamomeum

Native

Moist. Swamps, streambanks. Full shade.

Spring to early summer

12″ to 36″

Cinnamon fern has conspicuously clumped sterile fronds up to 60″ long. In Minnesota they are unlikely to reach more than 36″ long at maturity. They are slightly tapered at the base. The lowest pinnae are more than half as long as the longest one. On the undersurface of the leaf there is a small area of woolly, cinnamon-colored hairs at the base of the pinnae.

Fertile fronds are much shorter and rigidly erect. They are green when they emerge and turn cinnamon-colored when they mature. After spore dispersal they fall to the ground and become inconspicuous, making identification more difficult.

Interrupted fern (Osmunda claytoniana) fertile fronds are silimar to sterile ones but taller, more erect, and with brown fertile fronds in the middle of the blade that fall off early in the season leaving a gap. The sterile pinnae do not have a tuft of hairs at the base.