The only extant native population of Astragalus tennesseensis A. Gray in the midwest was monitored from 1984 through 1995, during which time there was a severe drought that extended from 1987 through early 1989. The total population size reached a low of 14 plants in 1989 and a high of 176 plants in 1990. The average number of plants present per year was 76.3. The average life span for 29 plants that survived their seedling year was 3.6 years, and the longest any plant lived was 7 years. Mortality of mature plants was due primarily to stem boring insect larvae. Mortality of seedlings in their first year was 67% and was apparently caused by moisture stress and uprooting by wind.