Numbers of flowers and their arrangement in time and space greatly influence levels of pollination and fruit set in natural populations of flowering plants. We examined relations between flowering phenology, floral display and reproductive success in the nectar-producing orchids Sirindhornia mirabilis, S. monophylla and S. pulchella in Thailand. We found each species to be self-compatible and dependent on insects for pollination. Sirindhornia mirabilis exhibited prolonged longevity of individual flowers and produced more flowers per inflorescence — features that may have evolved in response to low visitation rates. Patterns of reproductive success in relation to floral display suggest selection for increased inflorescence size in S. mirabilis and S. monophylla, but this may be counterbalanced by selection for a sustainable annual fruit set. In all three species, the female (and in S. mirabilis also the male) reproductive success decreased from the basal to the apical part of the inflorescence. Against this background, we propose a hypothesis for explaining differential fruit set in polinator-rewarding orchid species.