Abstract: Flowers are necessary for sexual reproduction in angiosperms; however, they are also costly for a plant to construct and maintain. Therefore, to maximize efficiency of resource expenditure, flowers are expected to senesce shortly after reproductive function is complete. In protandrous plant species, male sexual function precedes female sexual function. In such plants, one might expect the male phase to terminate shortly after completion of male function (pollen removal) and the female phase to end with floral senescence shortly after female function (pollen receipt) has been achieved. The relationship between pollen removal and the length of the male phase, and between pollen deposition and the length of the female phase, was explored in Campanula americana, a protandrous woodland herb. Three observational and manipulative experiments were performed on both natural and greenhouse-raised individuals to address (a) whether fulfillment of sexual function affects duration of the floral sexual phase, and (b) what patterns of pollinator visitation saturate male and female function in a natural population of this species. As predicted by theory, pollen removal significantly decreased the length of the male phase, and pollen deposition significantly decreased the length of female phase in Campanula americana. In a natural population, sexual function saturation for both gender phases was found to occur within a few hours of morphological sex phase onset. However, in contrast to theory, each sexual phase was found not to terminate immediately upon completion of sexual function.