Where the green ferns grow

Photos and story by Scot Stewart

“I fell in love with flora of all types, especially ferns. Loved the sparse

structure and repetition of shape––almost fractal.”

–– Jack Dorsey

 They were the fodder of dinosaurs and grew to the size of trees. They had foot-long dragonflies light on their fronds. It was 359 million years ago. Today, like the dinosaurs and dragonflies, they are much smaller. Ferns started out in the Mississipian or early part of the Carboniferous Period of the late Paleozoic Era, a time that lasted from 541 to 252.17 million years ago.

Much of the early knowledge of ferns comes from fossils formed a little more than 300 million years ago. Two great places where these fossils have been found are near St. Clair, Pennsylvania, and Wilmington, Illinois, both in coal country. Many of the fossils produced during the Carboniferous Period occur near coal deposits formed from about 300 to 360 million years ago. As large tree ferns and other plants growing in swamps died, they fell into the water for the centuries. Low sea levels during this time created large areas of swamps and the plants there took large amounts of carbon dioxide out of the air and returned the oxygen. So much oxygen was being created the levels in the atmosphere were 14 percent higher than now.

Decomposition was extremely slow because bacteria and fungi had not evolved to the point where they could break down lignin and cellulose, two of the large molecules in the plants containing carbon. From time to time floods washed soil over the layers of plants, halting decomposition completely. The high carbon concentration was retained as heat and pressure slowly turned the mass into coal.

Some remnants of life were trapped in silt near the edges of the coal layers fossilizing them. Occasionally minerals like iron were able to precipitate, or settle out of the water too, surrounding plant parts and dead animals creating fossils. Fern fossils in shale along the coal lines can be found at the Pennsylvania site. Great concretions containing fern fossils have been found in the Mazon Creek formations in Illinois. The oval shaped rocks are split open to reveal their trapped treasures. It is from these fossils that a clearer picture of how ferns developed has been painted. Their fossils have also given paleontologists, climatologists and others a greater opportunity to understand how the earth has changed over time.

Ferns reproduce by spores, not seeds. The process is called an alternation of generations. The leafy growths on fern stems are called pinnae. Some of them, particularly the upper leafy sections have structures on their undersides called sporangia—they produce spores, millions of them. Some estimates all the sporangia on a single plant of some ferns can produce more than 50 million spores in a season.

Ferns and their allies during the Paleozoic Era produced more spores—much more. Some fossil layers were made up entirely of spores, up to 50 centimeters thick, nearly 20 inches, according to Cecil Billington’s account in Ferns of Michigan. Because organic material becomes compressed as it metamorphoses, it is thought the original layer of spores may have been eight times thicker, 9 to 12 feet thick.

Spores develop into an intermediate phase in the life of a fern, a gametophyte called a prothallium. It is a small, sometimes heart-shaped plant about the size of a nickel growing on the forest floor. The prothallium produces male and female structures and they produce cells needed to produce a fertilized zygote, a sporophyte, and it begins growing on the prothallium. The new sporophyte then matures into the new fern, growing from a base that thickens into a structure called a rhizome, similar to other flowered plants. The development of this new plant is an amazing process, starting from a miraculous, microscopic spore blown by the wind to a new site.

“Only spread a fern-frond over a man’s head and worldly cares are cast out, and freedom and beauty and peace come in.”

— John Muir

Today, ferns in Michigan, although they are flowerless, are the gorgeous, green trim decorating the forest floor, adding extra green detail to new openings, stream edges and the feet of many large trees. Many are evergreen and add a surprising bit of color to a brown, nearly leafless landscape. They are among the most advanced of the non-flowering plant, the mosses, liverworts, equisetums (horsetails) and club mosses (lycopodia). They live in a wide variety of places—from dry open fields fresh from recent forest fires, to damp shady glades and sandstone rock crevices. The 65-year-old classic, Ferns of Michigan, by Cecil Billlington, Cranbrook Institute, 1952, while a bit dated, is still one of the best guides to Michigan’s club mosses, horsetails and ferns. It contains line drawings, range maps (missing a few newer sightings), natural history profiles and general information about the plants. It is still available through a variety of online sources for less than $5.

There are nearly 50 species of ferns in Michigan and around eight allies—the moonworts and grape-ferns, and a species called adder tongue. These three are interesting relatives, easily overlooked due to their small stature and limited vegetation. The former two get their names from their clusters of spore-producing structures that look like grapes and their transitory lives among the mix of other ferns, wildflowers and grasses.

Bracken ferns may be the best-known ferns in Michigan. Their three frond formations spread across many open areas and along roadsides. After a fresh rain they bring a crisp, green fragrance to the land. When they first emerge, and their curled, violin peg head tips are just emerging from the ground slowly unraveling, they are often picked as “fiddleheads”—fresh greens to be par-boiled and topped with melted butter, with freshly caught brook trout and fried morels. Later it is necessary to push through them to reach blueberry and blackberry patches for summer picking.

Hart’s tongue fern is one of the rarest in the Upper Peninsula. It is a relic of the end of the Pleistocene Epoch 11,700 years ago. Endangered in the United States today, it’s found in only a handful of states: Michigan New York, Maryland, Tennessee and Alabama. Hart’s tongue thrives in limestone cracks and pockets usually close to the soil. Its leaves are a shiny deep green, looking positively tropical. It is one of the true gems of the Hiawatha National Forest.

Walking fern is another eastern Upper Peninsula fern of the limestone forests. Like the hart’s tongue, its limited range in heavily forested, moist areas makes it difficult to find. Sometimes though, they do develop in large clusters, spreading from rooting leaf tips, allowing them to walk across rock faces and other calcareous (limestone) areas as they spread.

A positively mesmerizing fern found mostly in limestone-sandstone areas of the eastern Upper Peninsula is the maidenhair fern. Its narrow, dark mahogany colored stem spins in a spiral about a foot up then explodes into a spray of fine leaves. It is one of a number of large ferns found in the rich, damp soil along the lower reaches of the trail to Laughing Whitefish Falls, near Sundell, in Alger County. They double up in the fall to turn a bright golden color, highlighting the now ebony colored stem even more.

The wet remnant of Marquette City’s swamp north of Lakeview Arena is a great place for large ferns like royale fern, ostrich fern and smaller ferns like the sensitive fern. The larger are quite beautiful, spaciously leafed ferns. The sensitive is a simple small fern common along streams and even some ditches. All three produce separate fertile fronds, which bear the spore-producing structures. These fronds are a bright, deep golden color when they are producing spores.

Another large fern found on slightly higher, drier ground is the interrupted fern. Its delicate long fronds bear fertile pinnae in the middle of its greenery. After their spores are produced, the fertile pinnae dry and wither, leaving a space, hence the name interrupted fern.

Rock outcroppings are home to Woodsia, brake and polypody ferns. All are much smaller, delicate looking ferns. The Keweenaw Peninsula is a terrific place to look for all of these and other harder to find ferns. The only place several are found in the U.P. is the Keweenaw.

Plenty of polypody ferns are found in the large cracks in the boulders and rock outcroppings along the Sugarloaf Mountain trail north of Marquette. These hardy ferns dry out during the winter but have come back to life with the warmer conditions of spring.

Some of the slender cliff brake ferns and northern holly-ferns are easy to find along the Pictured Rocks National Lakeshore trail. One of the best spots for a great diversity of species is on the stretch of the trail just east of the Miners Beach parking lot. With a maze of sandstone cliffs, small creeks, waterfalls, and damp, rich shaded soil, the conditions are perfect for a wide range of species.

Ferns are an amazing group of beautifully designed pieces to the natural history puzzle of the region. They create a delightful addition to the list of plants to look for while outdoors as artful patterns in nature’s design, a roosting spot for a cranefly or dragonfly or an evergreen sprucing up a spot along a trail still filled with melting snow. With so many to find, a good field guide is a helpful addition to a trip outside. It’s another part of the great outdoors to keep you amazed and delighted.

MM

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