Ferns are ancient plants that have proved adaptable and resilient. Ferns grow on sea-sprayed cliffs, in the crevices of rocks and bluffs, in lakes and rivers, in high mountainous regions and even in semi-deserts. They grow most abundantly, however, in the shady, moist understory of temperate forests and in rainforests at all latitudes, where they often grow on trees.
Of the 10,000-12,000 species of ferns and "fern allies" living today, only 69 are found in Missouri. Fern allies are species of plants that have been historically grouped with the true ferns because of similarities in reproduction and their internal systems for the circulation of water and food. These species include horsetails or scouring rushes (Equisetum), quillworts, and spike (Isoetes) and club mosses (Lycopodium and Saliginella).
Missouri's ferns and fern allies can be traced to ancient climatic or geographic connections to northern forests, to dry regions of the southwest and to the moist, warm tropical forests of the Central America and the Caribbean.
Hay-scented fern (Dennstaedtia punctilobula) and club mosses (Lycopodium), for example, once grew throughout boreal forests. The purple cliff brake (Pellaea atropurpurea), the lip ferns (Cheilanthes spp.) and the rock spikemoss (Selaginella rupestris), on the other hand, have southwestern relatives, and the resurrection fern (Polypodium polypodoides var. michauxianum) has tropical roots. The kinds of conditions ferns are growing under can be clues to where the ferns came from.
It is easy to identify most Missouri ferns by their unusual leaves or fronds-slender stalks (stipes), together with their much divided, lacy and delicate leaf blades. There is considerable variation among fern leaves, however.
The leaves of walking fern (Asplenium rhizophyllum), for example, have long tapering, undivided blades while those of bracken fern (Pteridium aquilinum) are divided into three blades. Fern leaves range in size from under 1/16" in the eastern mosquito fern (Azolla caroliniana) to just under 5' in the larger ferns-bracken, log, cinnamon and royal.
Unlike mosses and algae, ferns and fern allies have a vascular system for carrying nutrients and water throughout their roots, stems and leaves. And, unlike flowering plants, they do not have flowers, fruits or seeds.
How ferns reproduced without flowers and seeds remained a mystery for many centuries. During medieval times, people believed that ferns produced flowers and seed invisible to the human eye.
By the mid-18th century, scientists had discovered that fern "seeds" were actually very small spores produced in tiny, one-cell thick capsules called sporangia. These typically grow in dark patches called sori on the underside of the frond segments or on separate stalks. When the sporangia mature and dry, wind or water disperses the tiny spores.
Ferns release millions or even billions of spores during their lifetime. If the spores settle on a suitably damp surface, the spores germinate to produce a pad of delicate green tissue less than one-half inch long called a prothallus.
Gametes (egg and sperm) are produced in separate areas on the underside of the prothallus. Their union produces an embryonic plant that will develop into a fern. Union of the gametes requires the presence of a thin film of water, which is one reason ferns are generally restricted to moist, shady areas.
In ancient times, people believed that the physical characteristics of plants were clues to their potential effects on humans. The myth developed, for example, that fern seed could bestow invisibility upon the bearer. Along this line of thinking, people also believed the heart-shaped leaf of wood sorrel could cheer the heart, and the yellow flowers of the celandine were an effective treatment for jaundice.
In the past, ferns have been used to treat everything from dandruff and the common cold to smallpox, diabetes and insanity. Scientific evidence supporting the effectiveness of many of these uses is generally lacking. A number of ferns, including the southern maidenhair fern (Adiantum capillus veneris) that grows in parts of southern Missouri, are still used by herbalists to treat a variety of disorders.
People have long used ferns for weaving, thatching and decoration, for packing and shipping goods, for dying various materials and for making soap, glass and fertilizer. In some countries, ferns provide a food source, although they are generally considered unpalatable.
In the western world, ferns in the fiddlehead stage are generally considered edible. The fiddlehead or crosier refers to young ferns whose fronds are still tightly coiled.
People commonly sauteed fiddleheads in butter or ate them raw. In 1994, restaurant diners in New York became ill after eating the fiddleheads of the ostrich fern (Matteuccia struthiopteris), which is found in north central Missouri and in gardens statewide. The Centers for Disease Control now recommend boiling fiddleheads for 15 minutes or steaming them for 10-12 minutes before sauteing or serving.
Caution should also be exercised in eating the fiddleheads of the bracken fern (Pteridium aquilinum), which grows primarily in the southern half of the state. These fiddleheads are an ingredient in Japanese and other cuisines. The bracken fern fiddlehead, however, contains a number of harmful compounds that have been implicated in increased rates of intestinal tumors in regions where it is a frequent part of the diet.
Today, the most common use of ferns in the United States is decorative. People grow them in pots, in hanging baskets and in shady, moist areas of gardens. Homeowners and landscapers also plant ferns with other native woodland species when naturalizing the shady areas of yards and grounds under trees where it is often difficult to maintain grass.
Hot, dry summers, however, challenge Missouri gardeners attempting to grow ferns. Native Missouri ferns, already acclimated to the region, offer the state's gardeners an alternative to non-native species that may require more attention and care and may create off-site problems by spreading into natural habitats. For a list of native plant nurseries in Missouri, visit the Missouri Native Plant Society website at www.missouri.edu/~umo_herb/monps/Brochure_PDFs/6 Native_Plant_Suppliers.pdf, write to Missouri Native Plant Society, P.O. Box 2073, St. Louis, MO 63144-0073, or send a stamped self-addressed envelope to Missouri Department of Conservation, Grow Native!, P.O. Box 180, Jefferson City, MO 65102.
You can also grow native ferns from their spores. Anne Wakeman, of Rock Post Wildflowers in Fulton, monitors the maturation of the spores using a magnifying glass. When the thin covering over or around the sori begins to retract, she collects the frond and places it between two pieces of paper. She then places the spores-the small "dust spots" on the paper-in a commercially available, sterilized grow mix. A green and "mossy" prothallus appears from which the fronds will eventually grow.
Of course, the easiest way to enjoy Missouri's native ferns is to walk through the woods. Readers interested in identifying ferns can refer to the Steyermark's Flora of Missouri, Volume I by George Yatskievych. Additional pictures of ferns and fern allies, as well as distributional maps, can be found on the Southwest Missouri State University herbarium website.
Like many of our smaller plants, ferns are often overlooked where they do not grow abundantly. Take time to get to know Missouri's ferns and fern allies, and you will be rewarded by the surprising variety in this old and venerable group of plants.