Doesn’t this little fern look like an innocent beauty? Well, I’m here to tell you: it’s no ingénue!
This is ebony spleenwort (Asplenium platyneuron (L.) Britton, Stern, & Poggenb.), recognizable by the alternately arranged simple leaflets attached to a shiny black midrib. In this species the longer leaves are fertile. Can you see the brown undersides of the taller leaves in the photo? That’s actually hundreds of sori that have expanded and burst, sending thousands of spores into the air. The smaller, lighter-colored leaves in the photo are sterile – they don’t have sori. They are also evergreen, able to gather light energy and photosynthesize year-round.
Reproduction in ferns is fascinating – in biology class you study fern reproduction before moving on to “higher” plants (like flowering plants and conifers) and “lower” ones (like mosses), because once you understand how ferns do it, reproduction in the rest of the Plant Kingdom makes sense.
You may remember some of it from high school biology. If not, here’s a crash course.
But here’s the thing – ebony spleenwort is positively undiscriminating. Not only does it successfully reproduce with its own species, but put it within range of a mountain spleenwort, a walking fern, or a wall rue, and chances are you’ll be finding hybrid offspring in the area. Sure, there is hybridization throughout the natural world. But the spleenworts are responsible for so many hybrids that scientists have named the whole interbreeding phenomenon the Appalachian Asplenium complex. Some of the hybrids are sterile, but others can cross with their parent species or a different one entirely to produce still more hybrid offspring.
Promiscuity aside, these plucky little plants are a joy to come upon among the dry leaves on the forest floor on a December afternoon. Because our winter has so far been quite mild, the tall, semi-evergreen fertile leaves are still green, helping the hard-working little sterile leaves grab some usable light energy on sunny days like today.