Wildflower is published quarterly by the Wildflower Center. Its content is national in scope with articles about the conservation and use of native plants as well as news from the Wildflower Center. A subscription is provided to Wildflower Center members as a benefit of membership.
Fronds Fare Well - Summer 2011
The lady fern (Athyrium filix-femina) is in many respects what people think of when they think of ferns: a shade lover with long, wavy fronds composed of delicate leaflets many times symmetrically divided. Ferns are, in fact, highly diverse in appearance and the conditions in which they grow.
With enchanting qualities, ferns have stood the test of time
Article by Bibi Wein, Photography by Bob Fisher
THE BEAUTY AND MAJESTY OF FERNS have long captured the imagination of plant lovers everywhere, and writers both legendary and modern-day have extolled their mysteries.
In many cultures, ferns have been regarded as magical plants with numerous powers. In Shakespeare's day, eating fern seeds was said to enable a person to become invisible. A variety of legends prevailed about exactly where and when these seeds could be acquired – a difficult task, since, as we now know, ferns have no seeds.
Ferns hold a different kind of magic for many of us today: They evoke a powerful sense of the earth's deep history. In a memoir, "Oaxaca Journal," about a fern-hunting trip to Mexico, neurologist Oliver Sacks recalls how in his childhood ferns filled him with wonder because they "had survived, with little change, for a third of a billion years … dinosaurs had come and gone, but ferns, seemingly so frail and vulnerable, had survived all the vicissitudes, all the extinctions the earth had known."
About 345 million years ago, during the Carboniferous Period, before dinosaurs, birds or mammals, and some 200 million years before the first flowering plants evolved, ferns and lycophytes – another ancient group of spore-bearers – dominated a landscape populated by reptiles and amphibians. Those early fern species went extinct some 290 to 270 million years ago, but not before they or their relatives gave rise to lineages leading to present-day ferns, according to Robbin C. Moran, Ph.D., curator of ferns at the New York Botanical Garden.
Star cloak fern (Notholaena standleyi) is one of the most striking ferns of Mexico and the American Southwest.
To be or not to be...a fern
Imagine creating an enchanted forest from the ground up. You'd likely begin with some moss and then go on to the clubmosses and spikemosses, collectively known as lycophytes. These small, charming plants, many of them evergreen, thrive in the same moist habitats in which many fern species are found. Their myriad textures are tantalizing to the eye and soft to the touch. If this imaginary forest were inhabited by elves, surely they would rest each night among the ferns and their smaller lycophyte neighbors.
Until recently, lycophytes were known as "fern allies" because, like ferns, they are vascular plants that have neither seeds nor flowers and reproduce by dispersing spores. But new DNA evidence, along with the fossil record, shows that the lycophytes (which also include the aquatic quillworts [Isoetes spp.]) are not closest cousins to the ferns after all but have evolved along a different – and distant – branch of the botanical family tree. "Over the past 20 years or so, we've learned that ferns have more in common with seed plants than with lycophytes," says fern scientist Robbin C. Moran, Ph.D. "And ferns share a more recent common ancestor with the seed plants."
Some 1,200 to 1,400 species of modern lycophytes are living representatives of the world's oldest surviving group of vascular plants. Their leaves, which have a different evolutionary origin from other plants, are never lobed or divided, according to Moran. Commonly called ground pine, firmoss, princess pine or running pine, the clubmosses and spikemosses (Selaginella spp.) provide groundcover, sheltering smaller plants and holding moisture in even the thinnest soil.
Not all fern species are ancient. Moran estimates that 80 percent evolved after the appearance of flowering plants. But some of our most familiar ferns can be traced back to the age of the dinosaurs.
The large, strikingly beautiful Osmundas are among the first ferns to emerge in the spring. "Some [Osmunda] species have hardly changed for 200 million years – they are truly living fossils," explain George Diggs and Barney Lipscomb, authors of "The Ferns and Lycophytes of Texas." Royal fern (O. regalis) can reach 6 feet in height. Its widely spaced oblong leaflets, unlike those of most other ferns, resemble the leaves of a locust tree. It is widespread in moist habits throughout the eastern and central United States, as is the cinnamon fern (O. cinnamomea). The latter plant's name reflects the color of the woolly tufts at the base of each leaflet.
Fern allies – not true ferns but vascular seedless plants that also reproduce by spores – that retain characteristics of their extinct cousins are the horsetails (Equisetaceae). Widespread in a variety of habitats and often described as resembling bamboo, the horsetails are related to treesized Calamites spp. that flourished in the Carboniferous swamps. Calamites spp. and horsetails have round hollow-jointed stems that carry out all the plant's photosynthesis.
Some horsetail species produce whorls of branches from the stem joints. Species with unbranched stems are called scouring rushes. Some prehistoric scullery man or maid discovered that their rough stems, studded with tiny bumps of silica, make excellent pot-scrubbers. "They also conveniently occur along streams and riverbanks, where pots and pans were washed," Moran points out.
Worldwide, there are 13,000 species of ferns, found on every continent but Antarctica and most abundantly in tropical climates. About 420 species are native to the continental United States, and there are ferns in every state. States with many indigenous fern species are Hawaii, Florida and Texas, which has 123 native species of ferns and lycophytes – with a greater number in the arid western part of the state than the wetter east.
Bracken fern (Pteridium spp.) is the most widespread of all the ferns and in many places the least loved, although we've used it for centuries for thatch, basketmaking, livestock bedding, potash and food. "This fern or a closely related species occurs in multiple habitats on every continent except Antarctica," says Moran. It is known as "the preeminent weed of the fern family." Its resilient rhizomes can colonize an area quickly and are impervious to cold, heat, herbicides, fire – you name it – because they are 6 to 12 inches beneath the ground surface. Moran dubs it "the Lucrezia Borgia of ferns," thanks to its history of poisoning livestock, people and insects. But in some cultures, primarily in Asian communities, its fiddleheads are still cooked and eaten.
The fronds of most ferns pop from the earth in early spring in the form of fiddleheads. "So elegant is this spiral, so exquisite is its shape that the fiddlehead has become firmly associated with ferns in the minds of most people," says Moran.
Equally fixed in many minds is the iconic fern, a shade-lover with long, wavy fronds that are composed of delicate leaflets many times divided in mesmerizing symmetry. The lady fern (Athyrium filix-femina), widespread throughout the United States, fits this image, as do some of the Osmundas. But ferns are actually a highly diverse group, with species acclimated to some of the harshest conditions a plant can endure, and many bear little – if any – resemblance to our iconic fern.
TOP Northern maidenhair fern (Adiantum pedatum) is native from the Atlantic coast to the central Great Plains. BOTTOM Spikemoss (Selaginella oregana) with licorice fern (Polypodium glycyrrhiza).
"Plants with 'ferny' leaves aren't all ferns, and not all ferns have 'ferny' leaves," explains Moran. Some ferns resemble grasses or mosses; others are succulents like the widespread rattlesnake fern (Botrychium virginianum), the grape ferns (Botrychium spp.) and the adder's tongue ferns (Ophioglossum spp.), which have leaves that resemble those of lilies or orchids.
There are desert ferns (xerophytes) in the Southwest, with decidedly "unfernlike" leaves that may be leathery (Pellaea spp.), waxy (Notholaena spp.) or scaly (Astrolepis spp.) to help preserve moisture; giant tree ferns in the tropics; and epiphytes or air ferns that live on tree trunks high in the sunny canopy. Our most widespread epiphyte is the resurrection fern (Pleopeltis polypodioides), common from the coastal southeast through parts of Texas. Its fronds wither and turn brown in drought but quickly revive again when it rains, as if by magic. Of Cheilanthes species, or lipferns, a desert genus with several strikingly hairy species, researchers Hope Diamond and Lucinda Swatzell write, "Look closely at…the rock crevices in which they grow... Rock crevices, particularly sedimentary rock, silt catchments or humus mats on stone outcrops retain moisture…And remember, these ferns are adept at extracting moisture out of 'thin air.'"
So what makes a fern a fern? Until the end of the 18th century, everyone, including the great Swedish botanist Carl Linnaeus, believed that ferns had seeds. Botanists were well aware of the spores, which they called "fern dust," on the underside of the fronds but remained uncertain about their function until 1794, when British surgeon John Lindsay, stationed in Jamaica, noticed hundreds of young ferns popping out of freshly exposed soil. Expecting to find fern seeds at last, he put a pinch of this soil under his microscope but saw only "dust." He sprinkled the dust on top of some soil in a flowerpot and became the first human, as far as we know, to propagate ferns from spores.
Spores and seeds are completely different in structure. "Spores are simple microscopic one-celled structures, whereas seeds are complex many-celled structures usually visible to the naked eye," explains Moran. "Unlike seed plants, ferns depend on water to complete their typical life cycle. They grow in places where, when the time comes to reproduce, enough water is available for the sperm to swim to the egg." So what about those xerophytes? Desert ferns have deep roots and the ability to use every bit of available water.
TOP Western sword fern (Polystichum munitum) is a good choice for a Pacific Northwest garden. BOTTOM A close-up view of northern maidenhair fern (Adiantum pedatum).
Although 95 percent of the world's plants reproduce by seeds, spores have some distinct advantages. They are so small that ferns can make tremendous numbers of them, and they are so lightweight that they can easily be blown or otherwise carried for hundreds or even thousands of miles – which is why some species are found where we would least expect them, thousands of miles and/or oceans away from others of their kind.
Ferns are distinguished from other spore-bearing plants, like algae and mosses, by their vascular tissues, which conduct food and water and in tropical climates may grow strong enough to produce a tree-sized stem. And, like other plants that disperse their spores, ferns produce no flowers.
Nonetheless, their unique structures and textures make a strong contribution to the garden. Planted en masse, they can evoke wildness without disorder – unless you want a jungle, which is an option if you garden in Florida or Hawaii. Planted individually as accents or in containers or rock gardens, they invite a close look at the repetitive, almost mesmerizing patterns of the multiple leaflets that make up each frond.
Becoming familiar with these patterns is a first step toward beginning to identify ferns in the wild. But beware: fern-hunting – seeking out new or rare species in their native habitat – is probably second only to orchid-hunting in triggering obsession among the botanically inclined.