Echinacea tennesseensis (Beadle) Small is a federally endangered vascular plant species endemic to the limestone cedar glades of the Central Basin of Tennessee. The vegetation associated with each of the five known populations of E. tennesseensis was sampled in 1987, and its population demographics were analyzed based on observations of 492 marked individuals over two years. Although vegetative cover and species’ frequency varied among sites, Echinacea tennesseensis is an important component of the vegetation at all five sites, and a dominant at three sites. The vegetation of four sites is relatively similar, but the fifth site differs in species composition and reflects a history of human disturbance. In both growing seasons mortality was highest among the smallest plants. A critical stage of growth (>30 cm total leaf length) at which survivability increases was identified. Plants that have not reached this stage have only a 50% chance of surviving an extreme summer drought such as that of 1988. Nearly half of the plants that produced flowers in 1987 did not produce flowers in the exceedingly dry summer of 1988; however, of these, 68% flowered in 1989. In addition, mortality was higher in year 1 (1987-88) than in year 2 (1988-89). These differences between years are attributable to the higher rainfall recorded during the 1989 growing season, and they demonstrate that flowering is sporadic and most likely dependent on growing season rainfall.