A Fondness For Ferns
Cool shade, fragrant earth, lush green-all are reasons to relish Minnesota ferns.
By Janet Boe
Photography by Richard Haug
A few years ago, my botanist friends Carol and Steve Mortensen and I took a boat trip out to Bear Island in Leech Lake to look for one of Minnesota's nearly two-dozen rare ferns and fern allies (closely related plants, such as horsetails and clubmosses). We searched the northern part of the island, in shady, moist woodland-the preferred habitat of most of the world's more than 10,000 species of ferns and fern allies. The goblin ferns (Botrychium mormo) we found that day are among the smallest of Minnesota's 100-plus species of ferns and fern allies.
Spore Power. Ferns and their allies differ from mosses in that they have a vascular system-tubes that carry water and nutrients from one part of the plant to another. They differ from other vascular plants (flowering plants and conifers) in their method of reproduction. Flowering plants and conifers produce pollen and ovules and rely on pollination to produce seeds. Ferns and their allies are flowerless and seedless; they reproduce by means of spores, dust-sized structures held in small balls called sporecases.
Ferns differ from fern allies in two important features: leaf size and the arrangement of sporecases. Ferns have large leaves, sometimes called fronds. The leaf includes a large, expanded part called a blade and a stalk, or stipe. Sporecases occur in dotlike clusters, called sori, on the underside of leaves or in grapelike clusters on specialized leaves. In contrast, fern allies tend to have small leaves, and their sporecases are single on some leaves or grouped in cones at the top of the plant.
To reproduce, ferns and their allies shed spores, which land on the ground and develop into tiny plant forms, which are all but invisible to us. These tiny plants produce eggs and sperm that unite and grow into a leafy plant.
Ancient History. Ferns and their allies have been traced far back in the fossil record. More than 300 million years ago, relatives of modern-day clubmosses, horsetails, and ferns were abundant and diverse; some were tree-sized and scraped the backs of the reptilian forebears of dinosaurs. Remains of these plants became an important part of the fuel we know as coal.
As seed-bearing plants evolved several hundred million years ago, the huge fern relatives with their spore-based reproductive systems declined. Because the outer covering of seeds protects the tiny plant within, seed-producing plants were more successful than ferns. They began to take over, leaving much less space and sunlight and fewer nutrients for ferns and their allies. Today relatively few species of ferns and fern allies remain.
Ferning for Fun. While birders walk around with their heads up, Dale Yerger watches the ground at his feet because he loves ferning-hunting for and identifying ferns. Although ferns have their own specialized terminology, most people, including Yerger, find them a good place to start when learning plants.
Executive director of Deep Portage Conservation Reserve, Yerger started ferning years ago in Vermont and has kept it up. Now he looks for ferns on vacations with his family using A Field Manual of the Ferns and Fern-Allies of the United States and Canada by David Lellinger. He already has goblin fern on his list, but I've promised to take him along the next time I go looking for its rare relatives: pale moonwort, lance-leaved grape-fern, and Mingan moonwort.
To get started ferning, walk the trails in Savanna Portage State Park near McGregor-where moist, shady conifer swamps and maple--basswood forests hold at least 16 species of ferns and fern allies, including a few rare moonworts (Botrychium spp.).
Maidenhair-fern (Adiantum pedatum) grows in moist, deciduous forests with nutrient-rich soil. It is most common in southeastern Minnesota.
Round-branched ground-pine (Lycopodium dendroideum) is a common clubmoss with horizontal, underground stems. Its upright shoots resemble a tiny pine tree. Stalkless cones atop the leafy shoot hold sporecases. Clubmosses have been used in holiday wreaths and medicinal teas. Their spores have been used in fireworks, as powder in condoms, and for stage lighting.
Shining Clubmoss (Huperzia lucidulum) lacks horizontal stems, or rhizomes, that Minnesota clubmosses usually have. It has shiny, bright green leaves, hence its common name and species name, lucidulum, from the Latin word for bright or shining.
Water-horsetail (Equisetum fluviatile) is a common fern ally that thrives in ponds and other places with slow-moving water. It usually has branches. The horsetail genus, found around the world, might have been present 300 million years ago. Equisetum may, in fact, be one of the world's oldest living groups of vascular plants.
Bulblet-fern (Cystopteris bulbifera) is the only fern in eastern North America that produces well-formed bulblets for vegetative (asexual) reproduction. Bulblets form on the underside of the long, feathery leaf blade, then fall off and develop into new plants. This fern also reproduces sexually by spores.
Walking fern (Asplenium rhizophyllum) grows on shady, moss-covered limestone boulders in southeastern Minnesota. Leaf blades have a long, tapering tip, which bends to the ground and takes root, forming new plants. In this way the fern seems to be "walking" around.
Sensitive Fern (Onoclea sensibilis) has green, vegetative fronds that are easily damaged by frost. Fertile fronds are produced in August or September, have beadlike segments that enclose the sori, turn brown at maturity when spores are released, and often persist throughout the winter.
Royal fern (Osmunda regalis) has broad fronds with large, well-separated leaflets that make it look like a flowering plant. How did royal fern get its name? One possibility is that the genus was named after King Osmund, who ruled in the British Isles in the eighth century. Someone might have thought this species, the largest in the genus, was stately and royal-looking.
Cinnamon-fern (Osmunda cinnamomea) has pointed leaflet tips. It gets its common name from cinnamon-colored fertile leaves that appear in early summer, mature quickly, and wither after spore dispersal.
Janet Boe is the DNR regional plant ecologist in northwestern Minnesota.