Vernalization

This low temperature requirement for flowering, called vernalization, begins at germination. Vernalization is assumed to occur at temperatures between 0 and 18°C (Ahrens and Loomis, 1963; Tirone and Metzer, 1970).

Species needing vernalization do not flower when grown in a warm climate.

For some plants, however, exposure to low temperatures during winter is an essential step in their development. Two of these processes, vernalisation and the breaking of winter dormancy, have important implications for gardeners.

Furthermore, vernalization has been shown to override the late-flowering phenotype. […] Both VRN1 and VRN2 genes have been identified to be associated with vernalization.