All About Ferns

Fern History, Fern Care, Fern Culture

Where Ferns Come From

Ferns are as alluring as they are ancient, and growing a fern just gives you those ethereal otherworldly vibes – a place in time that’s neither here, nor there.

Before ferns, there were mosses, lichens, algae, and fungi scattered about and nothing tall grew on the landscape. The tallest primitive plants grew to be less than 1.5’ tall, and the landscape looked much like what Iceland looks like today–rocky, covered with moss, and not a lot of topsoil or organic matter. Ferns are different from earlier plants such as mosses, in that they have developed a vascular system – true roots, and xylem and phloem to transport water and materials throughout the plant. This vascular system allowed ferns to tower over mosses and grow to heights never before seen on earth–growing above 1.5’ was a big deal.
With a vascular system to organize water absorption and storage, ferns got bigger and colonized more environments previously uninhabitable by mosses. Hills, cliffs and mountains that were too dry for mosses were easily inhabited by ferns, and helped to keep these previously dry places moist enough to expand moss’ range. With the help of ferns, plants finally spread in-land.

Other proto-vascular plants also evolved alongside ferns. These early vascular plants (including ferns) came to dominate and colonize the mid-late Devonian landscape about 400-360MYA. Lycopods, which are not ferns, but cousins, evolved earlier during the Silurian ~440MYA and are grouped together with ferns, and the whole group is often referred to as “Ferns and Fern Allies”. During these times through the mid-Carboniferous (360-~335MYA), the continents were separate, and in different configurations than we know them today. This allowed water between the continents, which led to milder, wetter climates (FYI, weather is caused by large bodies of water between land. Can’t have rain without large bodies of water to evaporate and make clouds. That’s why Central Asia is a big desert…).

Again, while these continents were coming together, they formed shallow seas between them, allowing for highly humid weather patterns, and ease of dispersal for Ferns and Fern Allies. Ferns and Fern Allies became dispersed onto all land masses, and the early humid climate of 360-335MYA contributed to this. The coming together of Pangaea around 335MYA caused warming during the mid-Carboniferous, which accelerated plant growth, even as the planet began to slowly dry out from the seas being drained from the landmasses coming together. This entire period from 360MYA-300MYA is known as the Carboniferous Period, and is often called the “Age of Ferns”.

The Age of Ferns

The Age of Ferns was a period of change for both the earth’s landscape and climate. Great swamps and forests of ferns and other plants dominated the planet, and most of the planet at that time was warm and tropical. With ferns and their allies covering more of the landscape, and general plant populations increasing, they caused the atmosphere to change as well. During the Carboniferous Period, there were so many plants that the oxygen level of the atmosphere increased from ~15% to ~35%. Carbon dioxide levels fell by about the same amount–all of that free carbon was fixed by the plants into themselves, and eventually the soil. This led to periods of cooling, and a few ice ages in along the way, but nothing incredibly severe to threaten too much life on earth.

An artist’s rendition as a diorama of what a Carboniferous forest may have looked like.

It was during the Carboniferous Period that most of our coal and oil deposits were formed. Sea levels would rise and fall with the ice ages and shifting of the land masses, covering great swamps of plant life with sediments. The sediments built over time, crushing the plant matter under immense pressure, forming coal and oil. That’s right, coal and oil come from dead plants–particularly dead ferns and fern allies–not dead dinosaurs. Although, they still make for interesting archaeological discoveries. The removal of the greenhouse gas and carbon dioxide caused a drop in the climate of the planet, and it spurred an ice age at the end of this period.

The Great Dying

But over time, from the mid-late Carboniferous Period, when Pangaea formed (335MYA) from the crashing together of landmasses, the earth began to heat up due to the drying-out of the seas between the continents, as well as the slowing and changing of the ocean currents.
Perhaps “drying” isn’t the right term, but rather, water was forced out of the seas between the continents by the continents colliding together, raising the sea beds and forcing the water out. With the lack of seas to create rains, the supercontinent began to dry out and desertify. This desertification, along with several massive volcanic events, led to what is known as “The Great Dying”, or the Permian-Triassic (P-T) extinction event, around 252MYA. The climate shifted to hot and dry, and the lack of seas meant the lack of rains inland, leading to the supercontinent Pangaea being rich with rains, water, and life ONLY towards the outskirts of the supercontinent, but relatively barren inland (Think the way Australia is today or Central Asia). Most fern and fern-ally life was wiped out by the drying and lack of rain.

Pangaea around the PT Extinction 255MYA
Pangaea around 255MYA, the time of the Great Dying. This map shows low oxygen levels. Do not let the green color fool you – most of these places are brown deserts.
Credit: Nicolle Rager, National Science Foundation, based on Pangaea map data, Paleogeographic Atlas Project, University of Chicago

The Great Dying did not get its name from just plants dying. No, in fact, the entire world changed. Oceans acidified, currents which made weather waned away, and what little life that could exist on the edges of Pangaea had to constantly be barraged with extraordinary volcanic activity poisoning the air and water. In fact, this extinction event was so terrible, that life on earth never looked the same. The world before the Great Dying had life forms that we would not recognize. To put that into perspective, normally after an extinction event, some species die off, and life moves on with the survivors, which resembled their ancestors, but with new features. After the Great Dying, life was so changed, it was unrecognizable.

Life After The Great Dying

Ferns did not immediately spread out and diversify after the mass extinction. Most extant ferns (today’s ferns) actually evolved much later, during the Cretaceous Period, after flowering plants existed (about 100-70MYA). Why? The ferns that survived the P-T extinction were all high-light loving plants. And, as the earth was cooler and drier, Gymnosperms (plants that make seeds without flowers; cone-bearing plants) became the dominant life form. Gymnosperms already evolved at the time of The Great Dying, but were previously restricted to fringe habitats, since they preferred cool and dry or hot and dry habitats. If you think of pine trees (a common gymnosperm example), they live in high, cool and dry, and sometimes hot and dry places. As time progressed into the Triassic, and the planet stayed cool and dry, Gymnosperms radiated throughout Pangaea, and the forests became dominated with taller gymnosperms and seed plants towered over the landscape, shading most of the earlier ferns. The fact that the Triassic was much drier restricted fern radiation (spreading and diversity) until the end of the Triassic about 200MYA. In an attempt to compete with gymnosperms, some ferns evolved into tree ferns (Cyatheales) retaining the ancestral need for full sun, but unlike other ferns, grow into trees to reach for the light. Other fern growth was severely restricted to edge habitats or disturbed environments due to shading from taller plants.

Much of fern diversity was suppressed, and many lineages went extinct. Then, in the Cretaceous, ~100MYA, a separate lineage of ferns caught a lucky break. A horizontal gene transfer from a moss is what is believed to have saved the ferns that we know today. Plants exchange genes with the organisms that grow closely and around them, vectored by gene-transferring bacteria and fungi. A bacterium likely took the gene for making a special protein called Neochrome from a moss, and inserted it into a fern ancestor.

Why is Neochrome key? Well, it allows ferns to make use of shade or indirect light by increasing productivity from using red and far-red light. Plants mostly use red and blue light, some yellow, some UV, and almost no green light. In a shaded understory–the place where plant life grows beneath the forest canopy, where only a small percentage of light penetrates–the blue light is mostly captured by the tallest plants and does not bounce or bend well. Red and far-red light remains to bounce farther down in a higher ratio than blue light. Understory plants that can make good use of what light is available are more successful than the ones who can’t, and it’s this adaptation that allowed the ferns to conquer the understories of many environments. In addition, these ferns (Polypodiales) have adapted to other niches as well–some even becoming epiphytes, like the staghorn fern (Platycerium).

Fern Frenzy

Fast-Forward to Victorian-Era Britain (1800s AD), where there became an obsession with ferns. England’s cool, moist, foggy climate made it perfect for growing ferns and many people added ferns to their gardens. It wasn’t until the discovery that ferns reproduce by spores that they were able to be commercially produced. Until that time, when a fern died, a replacement had to be taken from the wild (something you should NEVER do!!!).

The combination of spore propagation, along with the advent of the Wardian Case, the world’s first glass terrarium, allowed easy care of ferns indoors. The Wardian Case also made Orchidelirium a craze at the same time. Fern collecting transcended social class and barriers at that time, and the aristocracy even encouraged the lower classes to “lift themselves up” by collecting and educating themselves about ferns. The first glass houses appeared and growing plants indoors became a pivotal symbol of “man’s triumph over nature” and shifted how society saw itself and its relationship to nature. We were no longer subject to the whims of nature, and this changed the philosophy of the late 19th and early 20th centuries.

General Care

Reproduction

Ferns do not flower, but reproduce by rhizomes and spores. Ferns have been known to purify the air, retaining ancestral genes to purify the air from when the earth’s atmosphere was more unfavorable than it is today. Although ferns get a bad reputation for being needy, by looking at their evolutionary journey, it’s evident that these ancient survivors are tough and can thrive, so long as their basic needs are met. Ferns are actually generally hassle-free. They also tend to grow faster than other tropical plants if they’re getting enough light.

Light

Bright, ambient light with a few hours of exposure to direct sunbeams is ideal for many. Increase humidity with light and heat. Will grow more rapidly with more light. Tolerant of just ambient window light in a window, but growth may be slow or non-existent. A tickle of direct sunbeams is ideal.

Water

Feel the media before watering. Water when the media has just dried out. Allow potting mix to half-dry out before watering. Soil can be perpetually moist, but not sopping-wet. Water more frequently during warmer and drier months and fertilize during growth periods.

Humidity

Some species require high humidity, and others don’t. Very thin-leaved ferns will perform better with higher humidity. Other ferns can tolerate lower humidity as long as their soil is not allowed to dry out. This is because, like nearly all plants, the majority of the water absorbed into ferns is through their roots. A constant supply of moisture from the roots is key to success with them. A regular misting with a squirt-bottle will help raise the humidity temporarily, but a humidifier is ideal if the fern is not in a bathroom. In bathrooms though, the humidity from showers is enough. Kitchens are the second-best spot for ideal humidity conditions, from boiling water and cooking at home.

Temperature

60°F-85°F. It’s best not to let it go below 55°F. If temperatures swing too low, some ferns may go deciduous.

Common Problems

Ferns commonly get crispy tips, which is a sign that they have started to dry out, or that their humidity is too low. Remember, no matter how high the humidity is, it’s no excuse to miss a watering.

  • SYMPTOM: Leaves turning brown and crispy at leaf edges
  • CAUSE: Under watered, low humidity, high salts, or potassium deficiency
  • SYMPTOM: Pale
  • CAUSE: Too much direct sun or underwatered (They can handle SOME direct sun indoors)
  • SYMPTOM: Dying lower fronds
  • CAUSE: It’s normal for ferns to shed. Clear it out as it happens.
  • SYMPTOM: Yellowing, possible black stems/leaves and a dead core, and/or lack of growth
  • CAUSE: Rot or root disease; overwatering

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