The Carlisle Mosquito Online

Friday, June 18, 2010



Cinnamon Fern

A cinnamon fern found at Great Meadows. (Photo by Kay Fairweather)

The underside of a frond. (Photo by Kay Fairweather)

Name: The Cinnamon Fern is Osmunda cinnamomea. It is a member of the Osmundaceae family which has only three members living in this area. The other two are the Interrupted Fern and the Royal Fern. All three are common in Carlisle. Reputable sources claim that the genus is named for the Saxon god of war, Osmunder, but provide no reason for it. Other sources have stories about Osmunder hiding his wife and daughter in the ferns to protect them from invading Danes, which doesn’t seem very god-like. The species name refers to the cinnamon color of the fertile fronds.

When and where seen: Cinnamon Fern is one of our more common ferns. They were in their full glory with both sterile and fertile fronds in the Great Meadows National Wildlife Refuge on June 6 along the River Trail. The ones along the Fern Trail in Great Brook Farm State Park, where there are thousands, are on an earlier schedule and the fertile fronds are already dying back and no longer cinnamon colored.

Distinguishing characteristics: Cinnamon Fern has separate fronds specialized for producing spores. Many ferns have only one type of frond and produce spores in localized spots on the underside of the leaves. Cinnamon Fern is easy to recognize when it is fruiting i.e. when its namesake spore-bearing fertile fronds are present. These cinnamon-colored fronds tend to stand straight up in the center of a whorl of outward-curving green sterile fronds. The sterile fronds are what the fern people call “twice-cut.” The frond is “cut” once into leaflets on each side of the main rib, and each leaflet is “cut” again into sub-leaflets. The second cut does not go all the way to the mid-vein. The fronds reach around three feet. When the fertile fronds have died back, the Cinnamon Fern looks most like the Ostrich Fern but there are two good ways to tell the difference. One is that the Cinnamon Fern sub-leaflets have forked veins and the other is that they have little woolly tufts where the leaflets are attached to the main rib. The tufts are the remnants of all the woolly fibers that covered the young frond before it unfurled. Hummingbirds have been known to take this “wool” to line their nests. Another difference is in the timing of production of the fertile fronds – typically May and June for the Cinnamon Fern and July for the Ostrich.

Sources: Peterson Field Guide for Ferns, Boughton Cobb; Royal Fern, How to Know the Ferns, Frances Theodora Parsons

Submissions: Please feel free to claim this space and write the Biodiversity Corner about any species that occurs in the wild and can be found in Carlisle.

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