C

Common Polypody, also known as Rockcap Fern and Rock Polypody, is a diminutive charmer that is more or less evergreen and, hence, a target of interest on just about every walk I take. As you can guess from a couple of its common names, Polypodium virginianum likes to grow on the exceedingly thin layers of soil the fern finds on rocks, and it's frequently in the company of mosses and lichens, which inevitably get there first and create the meager earth that will support the plants. P. virginianum also has a seemingly magical ability: it can tell the temperature and serve as a natural thermometer. The colder the day, the more the Polypody curls its leaves. Botanists call this talent thermonasty, and it joins the Rhododendrons in this skillset. Today is relatively warm, so the fern leaves are fully open. Soon enough, they'll be thermonastic.