To increase the understanding of between-sex differences in flowering patterns of dioecious plants, we tested two hypotheses: (i) sexual differences in year-to-year flowering variations result from differences in sensitivity to inter-annual variations of environmental factors; and (ii) the degree to which clonal integration within genets controls the flowering of ramets differs between the sexes. We monitored the flowering patterns of a dioecious shrub both at the ramet and genet levels over five years.

The flowering of genets and ramets annually fluctuated, relating with the hours of sunshine during summer in the previous year. The extent of inter-annual variation in inflorescence numbers was larger for males than females. There was significant inter-annual variation in the number of flowering ramets within male genets, but not within female genets. These patterns resulted from differences in the sensitivity between sexes to the inter-annual sunshine variation.

Moreover, male ramets exhibited a stronger sensitivity of flowering than females to the growth status of the genets to which they belonged. This suggests that individual ramets within genets bloom in an integrated manner rather than in an autonomous manner, and that the flowering of the lower-level module were controlled within the higher-level module differently by male and female genets.