Plants are required to synchronize not only for mating but also for successful seed maturation and dispersion. Synchronous reproduction has long been noticed in plants but none of the studies have focused on the role of germination timing and age difference among the individuals. To distinguish between age-dependent and environment-dependent synchrony, plants of different age and experiencing the same environment, are needed. We performed sequential seeding experiment using selected Arabidopsis thaliana accessions to test whether the reproductive behavior is influenced by germination timing or by seasonal condition. We found strong synchronization of senescence among cohorts regardless of their ages. In early flowering accessions, the influence of germination timing appeared to be mostly buffered by length of flowering period to achieve synchronization at senescence. They de-synchronized in flowering but by shortening the flowering period in later cohorts kept the senescence synchronized. In late flowering accessions, flowering period was more or less fixed to make the whole reproductive phase synchronized. Understanding the mechanisms controlling senescence synchronization may lead us to identify novel regulatory systems in plants.