Rare species are put at risk of extinction by our limited knowledge of them perhaps as much as by their limited numbers and habitat. The traditional management response has been passive and protective but it is becoming increasingly clear that preservation alone may be insufficient to safeguard many rare species. This study examined two populations of the threatened American hart’s-tongue fern (Asplenium scolopendrium var. americana) growing on the Saint Ignace District of the Hiawatha National Forest in Michigan. Objectives of the study were to make inferences about the fern’s ecology, to identify possible management strategies, and to make recommendations about further scientific study. Substantial variation in fern physical characteristics were documented both within and between the populations, with much of the variation attributable to micro-climate and canopy closure patterns. Demographic and geographic distributions further suggested that the fern’s reproductive behavior may be a response to heat and moisture variations resulting from the disturbance regime of northern hardwoods forests. Future management practices recommended include blocking conifer invasion into the sites and placing rocks within the colonies to see if fern habitat can be maintained by introducing rocks to replace the original ones as they are covered by litter. Studies of rock chemistry, fern genetics, bryhophyte relationships, and localized perturbations are also suggested as avenues for further scientific inquiry.