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As part of the genus Rhododendron, azalea is well known for its luxuriant flowering. High-quality flowering is essential and is considered to be a homogeneous bud burst in the forcing greenhouse and a continuous development to fully open flowers at indoor conditions. Growers continuously strive to improve the quality of their products and a simple question arose: “Why do azalea flowers not always open at indoor conditions?” We tried to answer this question by an in-depth physiological approach of the complex flowering process. In a first part, we focused on the effects of altered production processes on flower differentiation and flower bud dormancy. The increased use of plant growth regulators (chlormequat, paclobutrazol) did not affect flower differentiation, but increased the need for cold to break flower bud dormancy. Overall, large genotypic variations were found. In the second part of this research, carbohydrate metabolism and source-sink relationships were investigated. Based on photosynthesis measurements and forcing experiments, we defined the minimal light level needed to force azalea. The reasons for the two main problems with flower quality (non-homogeneous flowering and the arrest of flower development at indoor conditions) have been identified and can be prevented by correct production techniques. First, flower homogeneity is influenced by the amount of cold which plants receive during the dormancy period. Unfulfilled cold requirements will lead to non-homogeneous flowering. Second, the arrest of flower opening at indoor conditions is due to insufficient leaf starch reserves. Forcing plants to flower with the appropriate amount of supplemental light will prevent this problem by building-up reserves before sale.