We study the mechanisms by which the life cycles of annual and perennial plants are synchronised to the changing seasons. Arabidopsis thaliana is a model annual species and we have shown how circadian-clock regulation of transcription of specific regulatory genes and photoreceptor signaling combine to promote flowering of this species in response to long summer days. This process activates expression in the leaf of a protein that moves systemically to the shoot meristem and reprogrammes transcription leading to flower development. Perennial relatives of A. thaliana show interesting differences in their responses to seasonal cues, and we have developed Arabis alpina as a model perennial. This species flowers predominately in response to winter cold, and shows characteristic features of perennials such as only becoming sensitive to environmental cues after it reaches a certain age and cycling between episodes of flowering and vegetative development within its life cycle. Using a combination of forward genetics, genomics and comparative analyses in a phylogenetic context we have defined some of the mechanisms by which flowering regulation differs between annuals and perennials, contributing to the divergence of these life histories during evolution.