Walking Fern

With the arrival of spring and the proliferation of the wildflower display, I feel that our plants of the day have neglected many of the other major plant groups. While trees and shrubs are largely still dormant, not having let their leaves emerge from their buds and not having had time to send forth flowers and begin the reproductive process that culminates in so many different dispersal mechanisms for fruit, the wildflowers are not the only thing one can see at this time of the year. One group that we have written about in the past but has not been focused on lately are the ferns of our flora. The term “ferns” is a bit of a bit of a misnomer, describing a group that does not represent one lineage, that leaves out more closely evolutionarily linked species, and that is largely assigned by human judgment. Many “ferns” and their allies–plants like ground cedar–a group known as the Pteridophytes, are evergreen, and can be found out and reproducing early in the Spring.

Of the 45 Pteridophytes found on the Domain, 7 come from one family, the Aspleniaceae, many of the taxa of which will hybridize with each other to form a mixture of viable and non-viable hybrids (i.e. ones that can or cannot reproduce). These hybrids and their parents form what is known as the “Appalachian Asplenium Complex.” One of the more intriguing members of that complex is one of the parent ferns, the walking fern (Asplenium rhizophyllum). While its name hints at movement, do not expect to see fronds getting up and moving along the forest floor. The fern gets its “walking” moniker from its unique form of reproduction. As the fern grows, the tips of fronds extend outwards, eventually curving back downwards and making contact with the substrate. At this point a new plant will begin to grow from that tip, forming its own system of roots and eventually sending out its own fronds. This reproductive method creates large clumps of individual ferns that are all genetically identical.

But these ferns do not just reproduce vegetatively. Like most ferns, the underside of the fronds feature sori, pockets containing the spores that are responsible for sexual reproduction in ferns. It is this method of spore-driven reproduction that establishes new populations of walking fern and that is responsible for the hybridization that characterizes the ferns of this genus.

Walking Ferns are typically found on moist, limestone boulder faces, and are especially prevalent in stream beds low in the coves of the Domain’s forests.

Tags: Ferns, Shakerag Hollow, spring flora, Vegetative Reproduction