Descriptions of structure and flowering phenology of the tropical tree species Cedrela mexicana, Cordia glabra, Erythrina poeppigiana, Tabebuia rosea and T. ochrea neochrysantha are used to analyze and illustrate the complex relation between structure, vegetative development and flowering in tropical trees. Because of the strong positional differentiation within tree crowns and the repetition of vegetative and reproductive growth cycles in trees, flower develoment and its control are more complex than in herbaceous plants. Formation of terminal inflorescences, as found in Cedrela, Cordia and Tabebuta, regularly occurs at the end of a flush of determinate shoot growth; flower initiation, like shoot growth cessation, is controlled by internal, correlative factors rather than by environmental changes. Initiation of lateral inflorescences is usually preceded by growth cessation in the indeterminate, vegetative shoot, but the timing and control of flower induction in lateral buds are unknown. For many tropical trees, particularly those growing in seasonal climates, flower development is discontinuous, i.e., flower initiation and anthesis are separated by a prolonged rest period and must be controlled separately. Delayed anthesis is usually triggered by rehydration of previously water-stressed trees resulting from leaf shedding or, in dry habitats, by rainfall. Because of different degrees of seasonal water stress, leaf fall and subsequent anthesis in several species extend over 3-4 mo. The observed periodicity of anthesis in tropical trees is thus largely determined by seasonal changes in tree water status and is unlikely to be the result of selection for optimum tree-pollinator interaction.