Fiddlehead:

As the fern emerges from the ground in early spring it is covered in a light brownish-colored wool but it is quickly lost.

Leaves and stems:

Leaves are once compound, generally lance-shaped in outline, up to 40 inches long and 10 inches across, widest below the middle and gradually tapering at the tip end. Leaflets have deep lobes, rounded to slightly pointed, and forked lateral veins on the underside. The leaves are nearly erect to arching and grow in a circular clump with the fertile spike (if present) growing in the middle.

There is a persistent tuft of whitish to brownish hair on the underside of the leaf at the junction of the main stem and leaflet mid-nerve. Stem is green and slightly grooved on the upper side.

Spores:

In mid to late spring, 1 or more spike-like fertile leaves, nearly as tall as the sterile leaves, grow in the center of the leaf clump. Fertile leaves are hairy and composed of very small bead-like capsules (which contain the spores) that are initially green but turn cinnamon-colored with maturity. After releasing the spores, the fertile leaf dies and is inconspicuous.

Notes:

Since the leaves, size and overall structure of Cinnamon Fern, Ostrich Fern (Matteuccia struthiopteris) and Interrupted Fern (Osmunda claytoniana) closely resemble each other, they can be distinguished by the fruiting fertile fronds. If spores are not present, the easiest way to distinguish the 3 species is to turn over the leaf and see if there is a tuft of hair at the junction of the main stem and leaflet - only Cinnamon Fern has this feature. Cinnamon Fern was formerly known as Osmunda cinnamomea but was recently moved to genus Osmundastrum, presumably because genetic testing found it not as closely related to Interrupted Fern as previously thought. While in some areas of the country Cinnamon Fern may reach heights of 5 feet, it doesn't get quite that tall in Minnesota.