The quantity and quality of sexual reproduction may significantly impact long-term persistence of rare, clonal species. Trifolium stoloniferum, running buffalo clover, is a federally endangered plant inhabiting disturbed woodland, lawn, and floodplain sites in several Midwestern states. To explore possible connections between the reproductive ecology of Trifolium stoloniferum and the plant’s rarity, research was conducted to determine if the species is self-compatible and to evaluate the extent and quality of sexual reproduction in four Ohio populations. Flowers bagged at the bud stage in both the greenhouse and the field failed to produce seeds, while openly pollinated (field) and hand-tripped (greenhouse) flowers set seed. These results reveal that T. stoloniferum is self-compatible but does not autonomously self-pollinate. In 1996 and 1997, we collected senescing inflorescences in two large (>1000 ramets) and two small (< 270 ramets) populations. The following data were analyzed per inflorescence: number of florets, number of fruits, percent fruit set, seed set, and seed quality. Population measures of mean seed set per inflorescence ranged from 4.3 to 39.0 seeds in 1996 and 7.8 to 68.6 seeds in 1997. In both years, the smallest population set a greater number of seeds than either large population, and the largest population generated significantly fewer seeds than all other populations. Therefore, seed counts do not indicate a positive correlation between population size and reproductive success for this species. Potential reproductive problems for T. stoloniferum include low seed set and germination in large populations and dependence on pollinator service to produce seed.

Key words: clonal species, federally endangered, population size, self-compatibility, sexual reproduction, Trifolium stoloniferum