“Resource limitation” and “pollen limitation” represent incomplete conceptions of seed-production constraints, because they interact dynamically throughout the reproductive season. Instead, consideration of sink-source relations provides a more comprehensive explanation of reproductive investment. For example, when many ovules are fertilized within an inflorescence, the resulting strong resource demand (sink strength) may stimulate disproportionate resource allocation to seed development. With a carbon-tracing experiment and measurements of reproductive output of Thalictrum occidentale, a dioecious wind-pollinated herb, we illustrate such interaction of pollen and resource limitation. Reproductive performance correlated spatially among females. In addition, total ovule production correlated positively with the local density of males, whereas seed development correlated negatively with the local density of females. Ovule fertilization positively influenced carbon investment in reproduction and subsequent seed number and weight. Together, these results illustrate complex influences of external conditions on resource availability and interacting effects of pollination and resource allocation that are inconsistent with a strict dichotomy between pollen and resource limitation.