Open areas within otherwise forested regions captured the attention of both early settlers and botanists. Among these are cedar glades–open, rocky areas of variable size and shape. The designation “cedar” comes from the Eastern red-cedar trees, a conspicuous component of the mixed woods that surround glades. Found principally in the Central Basin of Middle Tennessee, cedar glades are ecosystems of considerable biological and geological significance.
The limestone that underlies cedar glades was formed during the Ordovician geological period some 500 million years ago. The weathering of this rock has resulted in thin soils that support an interesting assortment of plants, some of global importance. Several species are endemics found nowhere else.
Glade plants tend to be associated with soils of a particular range of soil depths. These zones are recognized as: (1) exposed rock (no soil; lichens); (2) gravely glades (soil 0-2 inches; several herbs, including Nashville glade-cress, Gattinger's lobelia, limestone fame flower); and (3) grassy glades (soil 2-8 inches; annual grasses, also Nashville breadroot, Gattinger's prairie-clover, and Tennessee coneflower).
The cedar glade microenvironment is a harsh, imposing one. Summers are hot and dry, and the thin, exposed soil dries out soon after rains. Winters are cold and wet; rains are more frequent, and evaporation rates much slower. Plants and other organisms must have life cycles synchronized with these changing conditions.
Once occupying approximately 5 percent of the Central Basin, cedar glades have been considerably reduced in extent by man's activities. As a result, some of the plants indigenous to the glades are in peril. The conservation of glades and other special habitats is, therefore, imperative.
Jerry M. Baskin and Carol C. Basin, “Cedar Glade Endemics in Tennessee and a Review of Their Autecology,” Journal of Tennessee Academy of Science 64 (1989): 63-74; Thomas E. Hemmerly, Wildflowers of the Central South (1990)