Fiddleheads and Fronds
Sensitive fern (Onoclea sensibilis)
By Scott Kobal, Natural Resources
Of all the plants that grow in DuPage County, no group seems to attract more curiosity and questions than the ferns. “True” ferns and closely related plants called “fern allies” make up only 29 of the 1,000 native species that grow in the county, but their intricate, often delicate symmetry makes them appealing to many forest preserve visitors.
Ferns and fern allies are members of an ancient division of plants that dates back to the Carboniferous Period 359 million years ago — if not earlier. Similar to grasses, trees and flowers, they’re “vascular plants,” which means they have stems, roots, leaves, and internal tissues that carry water and minerals and convert light, carbon dioxide and water into food, a process better known as photosynthesis.
Unlike other vascular plants, though, ferns and fern allies don’t use seeds to reproduce. In fact for decades botanists didn’t know how they did it, referring to them as “cryptogams,” meaning “hidden reproduction.” Eventually, scientists discovered that the plants relied on a method that predated seed production by roughly 40 million years: spores.
Sporangia on a frond of spinulose woodfern (Dryopteris carthusiana) © Robert Klips
Spores are dust-sized, single-celled bodies that develop inside sacks called “sporangia.” The specific way a plant produces spores and the ensuing path those spores take to develop into new plants determines if a species is a “true fern” or a “fern ally.” The sporangia develop on a plant’s “fertile” leaves, versus its “sterile” ones, but because sporangia can be different shades of red or brown, some first-time observers may mistakenly think they are signs of disease or pests.
Once the spores mature, the plants release them into the air, but few land in appropriate places to grow, and for those that do, the road to becoming a plant is complex. Unlike a seed that becomes a coneflower or an acorn that develops into an oak, a spore does not grow directly into a fern or fern ally. For most species, the spore first develops into a tiny heart-shaped plant, which then develops the male and female reproductive parts that release the cells that join to create a new plant.
Sensitive fern (Onoclea sensibilis)
To grow, ferns and their allies require specific temperatures, moisture levels and soil pH. Some require rock with particular mineral compositions. Like flowering plants, some can handle a range of conditions while other less-tolerant species have restricted distributions. In DuPage County, the majority of ferns grow in moist woodlands.
This time of year ferns are helping to fill in the bare spring soil, although in a slightly different manner than other plants. Fern leaves, which are also called “fronds,” develop underground and emerge in tight coils, which help them push through the soil. Because the young leaves resemble violin scrolls, they’re known as “fiddleheads.” (Specialty grocery stores carry certain species of fiddleheads in their produce department. Cooks prepare them like asparagus. Several kinds of ferns are carcinogenic, though, so never pick your own.)
Christmas fern fiddlehead (Polystichum acrostichoides) © Uli Lorimer
One of the more common species of fern is the sensitive fern, which also grows in marshes and other habitats. Its name may suggest it’s a less-than-hardy species, but “sensitive” refers only to the sterile fronds on the plant, which die back after the first frost. In southern Pratt’s Wayne Woods Forest Preserve in Wayne, sensitive ferns and marsh ferns were so numerous when the District purchased the land in the late 1980s it named the area Fern Meadows. Lady fern has an elegant appearance, as does the spinulose woodfern with its “spinule-” or spine-tipped leaves. Rattlesnake fern, which usually grows singly rather than in clumps, gets its name from its fertile leaves, which look like the snakes’ tails. Ebony spleenwort is one of the ferns that remains green year-round; you can see it through winter, provided the snow isn’t too deep. A personal favorite, though, is the maidenhair fern with its finely textured, somewhat frilly fronds and curved, fingerlike stalks. Unfortunately, this fern has become rare in DuPage County.
Maidenhair fern (Adiantum pedatum) © Uli Lorimer
Ferns are familiar to most visitors, but fern allies likely are not. To add to the confusion between the two groups, some allies have “fern” or “moss” in their common names.
Like true ferns, fern allies grow in different circumstances, sizes and shapes. Horsetail and its relatives do just fine in the gravel along railroad tracks and in other degraded habitats, but bulblet fern and purple cliff brake can survive only in shaded cliffs and canyons rich in the mineral dolomite. The water fern, a true aquatic species, floats, but bracken fern requires dry soil. The marsh club moss is so tiny that people often mistake it for a moss; the leaves of an ostrich fern can span over 3 feet. And although glade quillwort has narrow grasslike leaves, the always green trailing ground pine and other “ground pines” and “ground cedars” look like miniature trees (while adding to the list of confusing common names).
Common horsetail (Equisetum arvense) © Uli Lorimer
You can see images of all of these ferns and fern allies at dupageforest.org/ferns. DuPage County’s list may be short, but the beauty these plants bring to our forest preserves is endless.
Image © Suzanne Cadwell
Water fern (Azolla carolinana)