A given flower is open only for a single day, opening before dawn and closing in the afternoon. Flowers are self-fecundating and protogynous (with female parts maturing first), and will self-pollinate if they have not been pollinated by insects during the day. While many insects visit the flowers, only some bees actually accomplish pollination. The flowering period of "V. thapsus" lasts from June to August in most of its range, extending to September or October in warmer climates. Visitors include halictid bees and hoverflies. The hair on lower stamens may serve to provide footholds for visitors.