Ferns, Fronds, Fiddleheads Are Diverse
The local woodlands, wetlands and streambanks of the Chautauqua watershed beckon us to explore their gifts of natural beauty and biological diversity, and the complex community of creatures living there has much to teach us.
One lovely but often over-looked group of organisms, the ferns, represent a unique history lesson and ancient legacy of adaptation, longevity and survival. Ferns trace their earliest ancestry back 400 million years to the late Devonian Period, long before flowers and trees appeared on earth. During the Carboniferous period, from about 360 to 300 million years ago, many ancestral ferns, horsetails and clubmosses grew to tree size, forming vast highly-oxygenated, swampy forests over much of what is now Eurasia and North America. These forests supported an amazing array of creatures, including early amphibia and reptiles, giant three-foot millipedes and dragonflies with six-foot wingspans.
Remnants of these ancient plants and the solar energy they photosynthetically harvested were eventually transformed into today’s energy-rich fossil fuels, coal, oil and gas. One University of Massachusetts study estimated that each gallon of gasoline powering today’s vehicles represents 196,000 pounds of ancient plant matter. It is sobering to think that in less than 200 years humanity is burning our way through tens of thousands of years of prehistoric biomass and stored energy – and releasing all that carbon dioxide in the process.
Today’s ferns, numbering more than 10,500 species worldwide, are best found locally in shady, moist habitats and growing as understory plants in undisturbed wooded wetlands. They may be found in a variety of other habitats as well, growing prolifically throughout the tropics but extending well into the Arctic and even floating in quiet waters and tucked among the crevices of hot, dry desert rocks. Locally-encountered species include woodfern, Christmas fern, lady fern, cinnamon fern, interrupted fern, sensitive fern, bracken fern, New York fern, hay-scented fern and many others. Several are included in the NYSDEC Protected Plants list due to potential threats from exploitation and habitat loss.
Ferns help maintain the moisture content and stability of wetlands, filter out toxins (including heavy metals) and serve as bio-indicators of ecosystem health. They provide shelter and shade, nesting and resting sites for countless little creatures, and they have symbiotic relationships with soil fungi and other partner microbes. And while some young ferns are nibbled by snails, slugs and beetles, many species host defensive chemicals to deter herbivory. Some of these compounds even mimic insect molting hormones that interfere with development.
Certain ferns, such as bracken, can be toxic to mammals including cattle and horses and are carcinogenic when consumed in large quantities by humans. Others, like young ostrich fern, can be cooked and eaten like asparagus, while still others have been used medicinally by Native Americans.
All ferns have a life-cycle very unlike those of the trees and wildflowers around them, for they retain a more ancient mode of reproduction and never produce flowers, pollen, seeds or fruit. Instead, ferns are dependent on the production of vast numbers of single-celled spores and express two very distinct and dissimilar plant forms. The more obvious stage, called the sporophyte stage, is the fern we normally see. This form is composed of the often-frilly green fronds (leaves) which may be sub-divided into lacy little leaflets (pinnae) and even lacier tinier leaflets on the leaflets (pinnules); an underground, perennial stem (rhizome) with true roots attached; and spore-production capability. The genetically-unique spores are produced by the zillions in specialized structures called sporangia, either within separate, modified fronds (as in ostrich, sensitive and cinnamon ferns) or on the undersides of leaves in tiny dot-like clusters called sori (as in woodfern, Christmas and lady fern).
One study by Dr. Robin Moran of the New York Botanical Garden estimated that the sori on a single frond of woodfern could produce more than 7 million spores! Such spores provide the genetic diversity and potential for sexual propagation, and when the time (and humidity, temperature and season) is right, they are explosively flung from the parent plant and dispersed into the world on the wind. If all goes well, these tiny specks will find suitable habitat in which to germinate into teeny heart-shaped, sexually-reproductive gametophyte plants called prothalli that few people ever see. It is here that eggs and swimming sperm are created and where fertilization occurs if sufficient moisture allows sperm to reach the eggs.
If successful, these “little green valentines” will birth new sporophyte youngsters, which will eventually attain the size and appearance of the more familiar ferns once more. Once established, ferns may live for many decades, creating new fronds from the perennial underground rhizomes for years to come. Some, like those of Christmas and wood ferns, remain evergreen even under the snow, while the leaves of lady, cinnamon and sensitive fern die back each fall. Young tightly-curled replacement fronds, or “fiddleheads,” remain dormant throughout winter and patiently await the warmth and light of longer days to unfurl among the wildflowers in the season of spring.
Becky Nystrom is a Professor of Biology at Jamestown Community College, a founding trustee and former board director of the CWC, and a longtime CWC supporter and volunteer.
The Chautauqua Watershed Conservancy is a local not-for-profit organization dedicated to preserving and enhancing the water quality, scenic beauty and ecological health of the lakes, streams, wetlands and watersheds of the Chautauqua region. For more information, call 664-2166 or visitchautauquawatershed.org or facebook.com/chautauquawatershed.