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.