The Joyful Botanist: These ferns rock, and roll
Rock ferns will protect themselves from drought by curling into a tight roll.
Adam Bigelow photo
I’m a fairly serious person, usually sticking with facts, data and science. But occasionally I enjoy a good joke or a bout of silliness. Actually, anyone who has been reading these columns or has been on a walk among the wildflowers with me knows that silly puns and jokes are my bread and butter.
One of my favorites is teaching in the woods and, fully deadpan, describe the mosses growing on a tree as “Tree Moss” and those growing on rocks would therefore be called “Rock Moss.” You can tell because it’s growing on a rock, ba-dum-tss.
Then, when we come across ferns growing on a rock, people have a hard time believing me when I tell them that this is a rock fern. They’ll scoff and say, “yeah because its growing on a rock,” but they have no idea how true that is and how useful habitat or where a plant is growing and what lives with it can be helpful for identification purposes.
So yeah, that fern growing on a rock is a rock fern, or rockcap fern, in the genus Polypodium. That’s a lot of fun to say, Polypodium. The prefix “poly” means many, and the suffix “podium” translates to little foot, so polypodium to means “many little feet,” a reference to nodules on the rhizome that are said to resemble feet.
There are two species of rock fern found in the Southern Appalachian Mountains, common rockcap fern (Polypodium virginianum) and Appalachian rockcap fern (Polypodium appalachianum). According to distribution maps, their habitats overlap in the mountains. They also look similar and are hard to tell apart as they were only recently split out from one species in the science of taxonomy.
Rock ferns are observed growing on rocks (ahem) and have dark green fronds that remain aboveground all winter long. This is one of a handful of evergreen fern species that you can see in the winter woods, including Christmas fern (Polystichum acrostichoides) and marginal woodfern (Dryopteris marginalis), also called evergreen woodfern.
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The fronds, or fern-leaves, of rock fern are around 6 to 8 inches long, and 3 to 4 inches wide and are often found growing in spreading clusters. These low-growing ferns are interconnected by rhizome type roots and will grow together to form mats.
Rock ferns have a defensive characteristic to help protect them from the scarcity of drought. The fronds will dry up and curl themselves up into tight rolls. This conserves energy and creates a micro-climate to protect them from the lack of water. Once the rains come again or an attentive hiker shares some water from their bottle, the rock fern will rehydrate itself and unfurl to its full size again, ready to continue the work of growth and reproduction.
This capability is shared with a similar and related fern called resurrection fern, named for this trait of coming back to life after being rehydrated. The resurrection fern has one of my favorite botanical names, Pleopeltis polypoidiodes. I don’t think I’ve ever been able to say it without a chuckle and saying polypoidi-odi-odi-odes. Its ridiculous.
The rock ferns and resurrection ferns have a lot of good advice to offer us in addition to their silliness, especially as we lean into the lean time of the year and are experiencing economic and food scarcities. And that is, to fold in on yourself, hold on to what you’ve got, create a little comfortable habitat for yourself and your kin, and wait for the abundance to return. No matter how dry it gets, the rains will return. And as I’ve said before, no matter how long and dark the winter, the wildflowers will bloom again. I promise you, friends. Just hold on.
(The Joyful Botanist leads weekly wildflower walks most Fridays and offers consultations and private group tours through Bigelow’s Botanical Excursions. This email address is being protected from spambots. You need JavaScript enabled to view it..)
