It was just a little over two years ago that my friends and I came down with a severe affliction. Don caught it first and in no time Robb and I were infected. The symptoms were unmistakable: feverish minds, euphoria, aching backs, frequent confusion, blurry eyes, obsession…

What dread disease plagued us? Why, pteridomania, of course…


It started with Don and, as with all things Don, the spark was lit by a bit of folklore. Once upon a time, people believed that if the “seed” of a fern was in your shoe, you became invisible. It’s even in Shakespeare!

GADSHILL: We steal as in a castle, cock-sure; we have the receipt of fern-seed, we walk invisible.

CHAMBERLAIN: Nay, by my faith, I think you are more beholding to the night than to fern-seed for your walking invisible.

           Henry IV Part 1, Act 2, Scene 1

Who wouldn’t want to be invisible? We needed to find fern-seed! This meant finding ferns. As we soon learned, there are a great many ferns to find, if only you take the trouble to look.

Even in February, there were ferns to find. A few lucky ferns stay green over the winter.

Christmas Fern. Haverford Reserve, PA.

We were familiar with the ubiquitous Christmas Fern. In fact, Don is entirely too familiar with it; Robb and I never miss a chance to point it out to him whenever we spot one.

Christmas Fern. Haverford Reserve, PA.

Christmas Fern has an “auricle” – a funny little bump on each pinna at the rachis. Some say it looks like a Christmas stocking. Others think it earns its name from its evergreen habit and use in holiday decorations.

Sensitive Fern. Haverford Reserve, PA.

The next fern I met, in the blissful days before Fern-Fever hit, was Sensitive Fern, still one of my favorites.

Sensitive Fern. Tyler Arboretum, PA.

Early in the morning, one can find its fronds bedecked in dewdrops.

FUN FACT: “Pteridomania”, an excessive enthusiasm for ferns, swept Britain in the Victorian age. Everyone was crazy for ferns! Books about ferns were in high demand. Scientific knowledge about ferns took a big leap forward, propelled by amateur and professional botanists alike. Growing ferns in greenhouses and gardens was popular, as was collecting them in the wild to display in the home. The plants also became a decorating motif. Ferns appeared on everything: pottery, sculpture, fabric, glass… If there was an item that could be decorated, it had ferns on it.

New York Fern. Haverford Reserve, PA.

New York Fern was the third fern I learned to identify, mostly by the size of its lowest pinnae.

Do you see how they taper down to almost nothing?










Once we really started looking for fern-seed, and ferns, we started seeing them everywhere.

We recognized Christmas, Sensitive and New York. Who were all these other ferns? We needed names! There are 380 species in North America! 90 species of ferns can be found in the Northeast. We bought a couple of books and dug in. We had a lot of learning to do.

In our new study of ferns, the first hurdle to overcome was fern terminology. Wildflowers and trees have leaves; ferns have fronds.

The lower stem is called a stipe. On top of that sits not a leaf, but a blade. The main axis of the blade is a rachis.

Each blade might be divided into pinnae, which may be divided into pinnules, which may be further divided into subpinnules. The number of divisions in a fern frond is an important clue to its species.

There’s a whole other terminology for the reproductive structures. We’ll leave that for another post.

Sensitive Fern. Haverford Reserve, PA.

Christmas and Sensitive have pinnae, but not pinnules. They’re considered once-divided, or pinnate.

Marginal Fern. Hickory Run State Park, PA.

This close-up of Marginal Wood Fern fronds clearly shows the pinnules on each pinna. A twice-divided fern, such as Marginal Wood Fern, is known as bi-pinnate. The pinnules show off the beauty of the prominent vein structure.

Lady Fern. Haverford Reserve, PA.

The edges of the pinnae or pinnules can be smooth, toothed or lobed. Lady Fern is toothed and almost lacy in appearance, compared to the smoothness of Marginal Wood Fern.









Some fern species look nearly identical. Take Evergreen Wood Fern and Spinulose Wood Fern, for example. How to tell these closely related species apart? Well, if it’s winter, you may see Evergreen – it is, as its name implies, evergreen – but you won’t see Spinulose.

In summer, we have a neat trick. Here are the lowest pinnae of a Spinulose Wood Fern. Take a look at the lowest inner pinnules. See how they are longer than the ones directly adjoining them? That’s the clue. On Evergreen Wood Ferns, those pinnules will be shorter than the adjacent ones.

Spinulose: long-short. Evergreen: short-long.

Except sometimes Spinulose and Evergreen hybridize… *SIGH*

Ferns grow in a variety of places. Sensitive Fern can be found in sunnier fields as well as woods. For the most part, though, ferns like shade and can be found in wooded places. Many prefer wet habitat, such as bogs or moist stream banks.

Royal Fern. Mitchell State Park, MI.

Royal Fern in particular likes wet feet; it can sometimes be found rooted in shallow water.

Royal and Cinnamon Ferns. Mitchell State Park, MI.

Perhaps this fern, like Narcissus, is captivated by its own reflection.

FUN FACT: Some ferns grow indoors! Everyone is familiar with Boston Fern, a ubiquitous house plant. Those fern-crazed Victorians took Fern-Fever a step further and built whole houses for their ferns. The last remaining free-standing Victorian fernery in North America is close by in Philadelphia, the Dorrance H. Hamilton Fernery at the Morris Arboretum of the University of Pennsylvania. The glass-roofed structure is filled with ferns – and lycophytes! – from around the world.

Some ferns like Christmas Fern are partial to slopes and hillsides.

Common Polypody. Shawangunk Mountains, NY.

Not all ferns grow in soil. Common Polypody (right) and Ebony Spleenwort are just two of the many ferns that thrive on rocky outcroppings or man-made walls.









Ebony Spleenwort. Hickory Run State Park, PA

No, this photo is not turned sideways!

Here, the Ebony Spleenwort is growing from a vertical wall.












Ferns are social creatures. They like to be in groups. Some form loose amorphous clusters.

Ostrich fern. Mt. Cuba Center, DE

Ostrich (right) and Cinnamon Ferns weave tight circular baskets of fronds.









Still others, like New York Fern, grow in widespread colonies that blanket slopes as far as the eye can see.

What the eye doesn’t see are the tiny cells at the heart of ferns’ complicated reproductive strategy: fern-seed. Or so people once thought…

But that is a tale for another day.

2 thoughts on “Pteridomania

Comments are closed.