Silvery bladderpod (Lesquerella ludoviciana) is an endangered plant in Illinois where plants are at the eastern edge of their geographic range, occurring in blowout areas of recovering sand prairies at the Henry Allan Gleason Nature Preserve. Little is known about its reproductive potential in these areas. The objective of this study was to characterize population size, production of reproductive structures, and viability of seeds. In June 1999, three populations were identified within the Preserve. For each population, plants with and without fruits (no flowers present) were counted, and population areas were determined. Seedstalks/plant, fruits/seedstalk, and seeds/fruit were counted. Seeds were germinated on filter paper in Petri dishes at 25C. The three populations varied in size from 275 to 2050 m2 with a total area of nearly 3000 m2. Plant numbers were 900, 225, and 10,300 in the smallest, intermediate, and largest areas, respectively. The percentage of reproductive plants was lowest (28%) in the largest area and highest (88%) in the smallest area. Reproductive plants produced 6.5 seedstalks/plant (from 1 to 20). An average of 17.3 fruits/seedstalk (from 0 to 43) and 2.4 seeds/fruit (from 0 to 7) were produced. On seedstalks, seeds matured first on the lower part and last on the upper part. Total seed production for all three populations was estimated at nearly 1,200,000 seeds. Seeds germinated without any treatments to break dormancy. In summary, reproductive potential does not appear to be limited by seed production or by seed viability. Rather, reproductive potential in silvery bladderpod must be limited by other factors.

Key words: Brassicaceae, germination, Lesquerella ludoviciana, reproductive potential, Silvery Bladderpod