If you grow spore-producing plants in your greenhouse, you might assume they’re all ferns. That’s easy to do, especially if label reads simply “green thing that likes humidity.” Botanists have a more detailed view. To them, there are not only true ferns but their leafy cousins who reproduces without seeds. The chart of classifications makes it clear: it is a pyramid, with true ferns called Polypodiopsida on one branch. On the next two branches is whisk ferns and horsetails. Casual gardeners tend to lump in clubmosses, too. These are really quite far away cousins and quite differently-leafy creatures.
Why does it matter? Since true ferns (and their allies) is not alike, knowing the difference matters. They aren’t exactly alike in their needs. They don’t grow the same way. They’re different than their ability to tolerate drought. They differ in their architecture.
Why Knowing the Difference Matters
Large leaves distinguishes true ferns. They have large leaves, split into parts, that capture light and look showy against a stone wall. They typically has sori on their underside. What’s that? Sori are clusters of spore cases. (Fern allies, by contrast, frequently lack any leaves or just have tiny ones called microphylls.)
For example: Horsetails depend on those jointed stems reinforced with silica. Feel it: rough. Whisk ferns just fork (leafless). That’s a detail. Makes a difference when you tend to them. Don’t expect a picky maidenhair to be happy where a tough old horsetail would do well, like in dry shade. Usually the attempt to treat them similarly mean frustration and brown tips.
If you zoom in on families among the true ferns, the number gets impressive. The two biggest ones, according to the infographic, are Polypodiaceae and Dryopteridaceae, both of which has well over a thousand species. And there’s one thing after another of them to try to figure out. This doesn’t mean you have to remember all their genera names to identify something growing on your bench. Examine it for the shape of its fronds, and where the sori, those spore clusters. Is located. Where the spores are tells you a good bit, says the chart: “Sori position appears to be a consistent indicator.”
If they’re covered by a fold of tissue, then it’s probably a Woodfern, which as the chart explains is a plant whose family name is Dryopteridaceae. They tend to grow naturaly in woodland settings; they are used to indirect light and cool, moist soil.
Are the sori positioned just along the edge of the leaf? You’ve got a Pteridaceae. Often this type of fern will curl up that same leaf and form a fake lid. Think of the beloved Maidenhair fern, for instance. It is especially fussy about water consistency.
If you grow plants indoors, you probably have only members of a handful of families. And even though there are hundreds if not thousands of species in the wild, it doesn’t matter. Take the Nephrolepis, or Boston fern, as an example. It is a Nephrolepidaceae. You know one when you see it; those fronds were once pinnately compound. They are ladderlike. They are tough and forgiving. This explains why they dominate houseplant shelving unit.
Compare that to the staghorn fern, a plant in the Polypodiaceae family that grows on other plants, meaning it hangs around in the wild clinging to trees. No wonder it wants to be mounted, not potting-soiled. And the infographic says the epiphytic specialists have naked sori. Their spore-producing structure has no protective flap over them. That’s because their life style demands it: Epiphytes must get their spores fast off into the air. Those woodland ferns can wait a little longer; they can get some protection.
There’s also the life cycle: What do you know about it? Ferns alternate generations. “The diploid phase is what we call the sporophyte; that’s the leafy thing you see.” And that brings us back to those little keys (the spores). How can you tell which ones are which? Partly by shape, and that shape also tells taxonomists which family they belong to (bilateral vs. Tetrahedral). If leaves resemble each other but the species aren’t obvious, knowing this can help.
Perhaps you don’t have a microscope on hand. So there’s more to understanding fern care than simply watering and making sure they stay clean. They require a thin film of water for fertilization. This is part of the reason ferns grow well where humidity is high. That is why you have misting bottles and humidity trays in your collection. It isn’t just about having something pretty to look at. It’s providing what they’ve evolved to require.
The next time you lift out a tagless frond, look closely. Examine its leaf division. Notice where those spore clusters grow. Feel the surface of the stem. Then think: This is no random jumble, this chart of classifications. If anything, it’s an actual how-to manual on maintaining live plants. All these green things in your house aren’t interchangeable. If you treat them that way, you’ve made the first mistake. Provide for each what its ancestors expected. They’ll respond by growing. It wouldn’t of seem so much work then; more like communication.