Commelina caroliniana Walter is an andromonoecious rainy-season weed. It bears staminate and hermaphrodite flowers in spathes. In some spathes, structurally hermaphrodite flowers of the third and fourth orders function either as male or female. The flowers are structured for cross-pollination. Events of floral biology suggest weak protandry which also contributes to cross-pollination. Large numbers of hymenopterans (nine species) visited the flowers and transferred pollen to stigmas. Whenever cross-pollination failed, selfing took over. Auto-fertility and self-compatibility indices revealed that the plants were self-compatible. Only some flowers of the third and fourth orders within a spathe were partially self-compatible. These facts notwithstanding, manual cross-pollination of flowers yields increased fruit and seed set.