Fern Cave NWR is named after the profusion of ferns the original explorers found in the Surprise Pit sinkhole. Another entrance used to feature the federally endangered American Hart's-tongue fern ("Phyllitis scolopendrium"). The fern population has disappeared since 1985 from a high of twenty due to the actions of illegal plant collectors. The fern grows in a small pit in Morgan County, but it is closed off due to the species being grown there and the cave it grows in is privatized.