The Mystery of the Unusual Polypody Fern

Cut-leaved Rock Polypody

The more time I spend outdoors, the happier I am. You might head out somewhere to see a particular plant, but you never know what surprises there might be along the way. That is the case with this wonderful frilly polypody, more correctly described as a Cut-leaved form of the Rock Polypody (Polypodium virginianum). In June 2021 I was hiking in the woods of Shutesbury MA with some friends, looking at interesting stone features. We happened upon a patch of these unusual polypodies growing on a boulder, next to a patch of normal Rock Polypodies. There was short distance between the two populations, each with just its own form, no mixing. I took photos and showed Randy, who called around to local fern people, who had not seen any like this. On the chance he might get a response, Randy contacted the fern expert Robin Moran and sent him some photos. He was wonderfully kind to respond, and told us it was not a new species or variety, but just a different form. He also stated at that time that he had only seen it twice before, in VA and WV. We were thrilled!

Since then we have been going back to check on the population at least once a year. We estimated originally that there were about 60 or so individual fronds of this frilly form in the patch. It seems pretty close to the same now. We have searched the area for more, and have only found 6 very small "patches" on the same large boulder. Most of these are only a couple fronds and still small in size. The mystery of this site is not only how this patch of Cut-leaved Rock Polypody developed here, but also how did the other little patches get started? We have looked for but never found any fruit dots (sori) on any of these Cut-leaved Rock Polypody ferns. There is a distance of about 4 feet of boulder between the main patch and the first little patch, and similar or greater distances between the other little patches. If there are no sori there are no spores to develop into new ferns, and it does not seem possible there could be a root system that extends through the rock. Are they all just starting vegetatively from fragments of a fern in the main patch that happen to land on the little ledges and holes in the boulder? We have shown this population to a few fern people, and we have not been able to figure it out yet.

As it says on one of our webpages, "There is something of the marvelous in all things of nature" (Aristotle). Happy exploring!

Posted: to PV Fern News on Sun, Sep 20, 2026
Updated: Sun, Sep 20, 2026