Wednesday, November 4, 2009

Discovering Wood Ferns

It was over 6 months ago in late April that I noticed the first fiddleheads of the spring. I was at home (my first home) with my parents, helping my mother recover from a fracture. And now a half-year later, Mom is stronger than ever, and the ferns are returning to their roots, fading in form and color.

The lacy lady fern and the arching cinnamon ferns, their burst of life above ground now over for the year, are brown and curled. Their fronds almost resuming the shape of the fiddlehead, just as they began the year.

Lady fern (Athyrium filix-femina) in early November

Yet the woods is still full of fern greenery. The wood ferns are there, carpeting the forest floor or tucked in small clumps among rock outcrops, now more visible after the understory shrubs and tree saplings have shed their leaves.

Intermediate wood fern (Dryopteris intermedia)
still lush and green in November

Ferns are a beautiful and diverse group of plants. My interest began early. I have A Field Guide to the Ferns on my shelf, with my father's handwriting inside, "Ellen Snyder 1972." I was not yet a teenager and I got this book as a Christmas present. Although some of the names have changed -- not only do botanists like to reclassify, but the ferns themselves have interbred -- the book is a treasure trove of still valid information about fern biology with delicate sketches of each fern.

Ferns have many different families. One of the biggest families is the spleenworts -- Aspleniaceae. This includes the lady-fern, the wood ferns, sensitive, Christmas and New York ferns, and more. The other family names are just as wonderful -- the royal fern family, the curly grass family, the polypody family, the filmy fern family, the bracken family, and the ever lovely maidenhair fern family.

The wood fern group (Genus Dryopteris) is a tricky bunch. They like to hybridize. I am sure they have confused humans since time began (well not that long since humans are younger than time....). Akin to identifying confusing fall warblers. For the warblers you need to look out for wingbars, eye rings, streaks, dabs of color, and behavior. The wood ferns require a good hand lens to look at veins, sori, and indusia and a study of the stalk or stipe for scales, the leaf or frond for once, twice, or thrice-cut leaflets (or pinna, pinnules, and pinnulets), and a knowledge of their preferred habitat.

One of my favorite wood ferns, is the marginal wood fern. It grows in rocky areas under oak and pine, its fronds are darker green and a bit leathery, and its sori (the fruit dots or spore cases) are along the margins of the underside of the leaflets. Why do I like it so much -- besides its beauty, I can identify it!

Marginal wood fern (Dryopteris marginalis)

Marginal wood fern leaflet or pinna

Underside of marginal wood fern -
note the sori (fruit dots) on the margins

Intermediate wood fern (Dryopteris intermedia) --
note the sori near the mid-vein, not on the margins

Intermediate wood fern, one of those confusing green ferns.

For the intermediate wood fern, take note of the second, upper pinnulet; it is longer than the first, upper pinnulet next to the main stem. That is the only visible difference between intermediate and spinulose wood fern. In the later the second pinnulet is smaller than first. You need to look at several fronds to be sure of the size comparison.

Go out and discover the wood ferns, still green in the woods. If you want to know if it is marginal, or intermediate, or spinulose, or crested, or one of the other many Dryopteris, take a hand lens and a key. Other still green ferns are there too -- Christmas fern and rock polypody. It is all fine greenery whether you know the names or not.

Earl J.S. Rook has a fine website on the natural history of the north woods with fine photos and descriptions of the ferns. See the wood ferns and other families there.

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