Ferns Through the Ages

Ferns grew in full sun three hundred forty-five million years ago when they were among the dominant plants on the planet. There were no trees to provide shade, and flowering plants were not to provide competition until two hundred million years later. Three hundred forty-five million years is quite a figure to contemplate, and adjusting to and surviving the earth's intervening vicissitudes is an incredible accomplishment that much of the flora and even the dinosaurs could not manage. According to fossil records and geological theory, the impact from an asteroid led to the extinction that doomed the dinosaurs sixty-five million years ago between the Cretaceous and Tertiary eras. It also led to a temporary (geologically speaking) fern spike as the fern flora rapidly filled the barren landscape and once again became the world's dominant plants.

Even as they apparently did historically, ferns today willingly colonize disturbed or burned areas. The reforestation on the 1980 volcanically destroyed flanks of Mount Saint Helens serves as a contemporary example. (Not surprisingly, Equisetum [horsetail] was among the leaders.) So it was that the ferns prospered and survive in variety today. Some, such as Osmunda claytoniana, believed to be the oldest continuously living fern species, can trace a family tree back two hundred million years. Others are, of course, younger (say two or three million years old, or about the same as humans). However, many of our most-familiar ferns are, at seventy-five million years old, truly juveniles, and one imagines that "new" ferns via hybridization or mutations are yet to come.

Ferns were once fairly uniformly distributed throughout the world, as evidenced by remnants of botanical relationships with prehistoric connections still in existence. On the land masses of the Southern Hemisphere, united before being separated by continental drift, South American blechnums have much in common with those of New Zealand. Eastern North American flora, including the ferns, has Japanese counterparts that were transported via ancient land bridges. Then as now, spores wafted on the air currents and were particularly significant in establishing island populations.

The uniformity of the world's floral distribution reached its zenith fifty million years ago when the earth was significantly warmer than today (envision tropicals in Greenland). It was interrupted as the ice ages developed. Plants migrated along with the warmth to the south and away from the glaciation. However, the upheavals of volcanic activity and the resultant creation of mountain ranges were influential here as well. In North America the uplifted mountains run north to south and consequently never presented a barrier to the southward floral shift or the forward movement and retreat of glaciers. In Europe the mountains run east to west, and the ice flows and plant survival were blocked resulting in a greater degree of plant extinction. As a direct effect the numbers of natives are far fewer in Europe than in the rest of the world.

In the social world, fern motifs appeared early in primitive artwork and have long been used in architectural ornamentation as well. By the mid 1800s, hand in hand with the fashionable interest in the live plants themselves, enthusiasm for ferns as art spilled into every opportune and marketable manifestation from decorating chamber pots to fine china. While not as extensive, their decorative uses continue to be popular today.

Scientifically, with their non-traditional reproductive system, ferns were very poorly understood botanically. Where were the flowers? And seeds? Speculation led to some fanciful theories, the most common being that the seeds, though there, were invisible. In turn this brought forth some magical connotations. Per the Doctrine of Signatures that gave life's issues and medical complaints a relationship with cures that were based on the visual attributes of plants, ferns with their "invisible seeds" offered, as oft quoted from Shakespeare (Henry IV, act 2, scene 1), the power to "walk invisible." First, however, one had to catch the elusive seeds or "fairy dust."Various theories, and one suspects a fair amount of revelry, surrounded the chase which was to be carried out on Midsummer Night's Eve with the sprinkling of the invisible seed powers showering and ready to be caught precisely at midnight.

Eventually, science caught up with the ferns. Their "dust" had long been noticed and sometimes confusedly considered as being pollen, but not otherwise related to

Ripe fern spores on the underside of a Dryopteris frond.

propagation. And, as accidents will happen (and someone must be alert enough to appreciate the significance), in 1794 John Lindsay, a British surgeon stationed in Jamaica, noticed that after rains quantities of ferns emerged from freshly disturbed soil (the best incubation sites in the wild for ferns today as well). Curious, he sprinkled some fern "dust" in a flower pot and soon discovered the development of the young plants', liverwort-like, small heart-shaped fertile structures, known scientifically as the gametophyte (sexual) generation. In time, these produced fronds, convincing Lindsay that he had found the "fern seed." He sent "dust" home to England along with sowing instructions, and fern propagation began in earnest at the Royal Botanic Gardens Kew as well as in horticultural and botanical circles throughout the country. Nurseryman Conrad Loddiges is credited with being an early proponent of carrying on propagation for commercial purposes and was the first to experiment with and recognize the value of shipping plants in Wardian cases some years later.

Although the discovery of the "seeds" answered some questions, true knowledge of the fern life cycle was yet several research stages later. In 1844 Karl von Nageli, a Swiss botanist, observed and described the presence of sperms in the intermediate generation. The egg-producing female structure was in turn discovered in 1848 (and rather impressively, hybridization shortly thereafter in 1853). Thus the alternation of generations, as we know it today, became science.

The Wardian case, an unbelievably significant contribution to science, agriculture, and commerce, was probably as equivalent in importance to growers as the discovery of the life cycle was to botanists. Again its origins were accidental, this time the result of an entomology experiment by Britain's Nathaniel Ward in 1830. He had placed a moth chrysalis in a covered jar and some time later discovered two plants growing in mold in the jar. One was Dryopteris filix-mas, which, we are told, he kept alive without additional water for nineteen years. Although it is noted again and again in horticultural literature that Ward was not the first to experiment with an enclosure for growing plants, his promotion of the discovery must be credited as being the most consequential.

Glass enclosures were immediately recognized as beneficial protectors of plants from the ever-present smog of London, preparing the way for the ensuing fern craze. An industry of case-making, with some taking on elegant designs and proportions, followed. Meanwhile, their life-sustaining properties soon became of obvious commercial value enabling the transportation of plants around the world. (Prior import attempts, including the collections by Captain Bligh, yielded very poor survival rates, although Bligh actually brought back some live ferns.) Thus it was that the Wardian case carried tea plants from China to India establishing the huge tea industry there. Rubber plants were transported from South America to Malaya. In short, all manner of plants, including ferns, were protected on their long voyages from port to port enabling new and profitable agricultural industries to flourish. The system continued in its practicality until relatively recently when it was replaced by the ubiquitous plastic bag and derivations thereof.

A fancy British cultivar of Polystichum setiferum at Lakewold Gardens.

Britain's well-documented Victorian fern craze followed and brought ferns to widespread public attention. Collecting parties were the vogue, and unusual fern forms with various aspects of the foliage departing from the norm were especially prized. Hundreds made their way to the market, and an entire vocabulary developed to describe the abnormalities. Although many were subsequently lost to cultivation, culti-vars in their assorted manifestations are popular and available to gardeners today.

In time the fern craze faded, perhaps from overexposure, and became subservient to other horticultural fancies. Happily, beginning in the 1960s, a balanced rejuvenation of horticultural interest in ferns returned and continues today, enriched by an ever-increasing body of knowledge, the support of enthusiasts along with their dedicated societies, and the ongoing introduction of varied plant selections from around the world. Long may it endure.

North American native ferns growing adjacent to a waterfall in a lightly shaded wild setting.

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