Flowering is the cornerstone of floricultural crops, regardless of class (bedding plants, herbaceous perennials, cut flowers, flowering potted plants); the only crop exceptions are those grown for their colorful foliage. During flower breeding and crop domestication, both public and private sector flower breeding programs must conduct research to discern the various control mechanisms for flower initiation and development. Important flowering concepts covered in this chapter include autonomous regulation (phase change; species, meristem size, and environmental factor affects), external regulation (photoperiodism, vernalization, devernalization, irradiance and light quality, and their interactions), irradiance induction, stress induction (ehtylene, water), flower development requirements (photoperiodism, temperature, stress), and dormancy.