Osmundastrum cinnamomeum (Cinnamon Fern)

Plant Info
Also known as:
Genus:Osmundastrum
Family:Osmundaceae (Royal Fern)
Life cycle:perennial
Origin:native
Habitat:part shade, shade; marshes, wet woods, bogs, swamps
Fruiting season:spring
Plant height:24 to 40 inches
Wetland Indicator Status:GP: FACW MW: FACW NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Fiddlehead:

[photo of fiddleheads] 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: Leaf attachment: basal Leaf type: compound

[photo of sterile frond] 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.

[photo of leaflet base] 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: Fruit type: spores on stalk

[photo of 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.

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More photos

Photos by K. Chayka taken at Long Lake and Sucker Lakes in Ramsey County. Other photos courtesy Peter M. Dziuk.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: luciearl - Lake Shore, MN
on: 2016-07-17 09:11:42

A few of these grow in the ditch at my parent's place. Wish I could transplant a portion to my property a mile away, but the roots are almost like tree roots making it almost impossible to dig up.

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