Plants come to flower after a certain period of vegetative growth. The process until plants come to flower is classified into three stages, that is (1) differentiation of flower buds, (2) development of flower bud, and (3) opening of flower. The differentiation of flower buds is the most important turning point in this process, and the plant's life cycle switches from vegetative growth to reproductive growth. The switching from vegetative growth to reproductive growth is called "flowering". Flowering physiology is the study aimed to clarify the mechanism switching the mode of growth from vegetative to reproductive.
　　Flowering occurs when flowering genes are activated. The activation of the flowering genes occurs autonomously or is triggered by environmental factors. Autonomous flowering occurs when plants reached a certain age. The environmental factors triggering the activation of flowering genes are photoperiod, low temperature and various stresses. Photoperiodic flowering regulated by photoperiod and vernalization regulated by low temperature have been well studied.
　　Recently, flowering is being studied by molecular biologists and molecular genetists. Studies on flower morphogenesis have rapidly developed in the field of molecular biology and molecular genetics. Under such circumstances, the terminology of flowering has come to be misinterpreted and flowering is often confused with flower morphogenesis. Accordingly, it is necessary to clarify the definition of flowering.