The transcription factor LEAFY is a master regulator of flowering and of flower development. It acts as a component of a switch that mediates the transition from the vegetative to the reproductive phase of plant development. Auxin is a plant hormone with many different roles in plant growth, including the induction of new primordia of both leaves and flowers at the shoot apex. We report that LEAFY acts in part by controlling the auxin response pathway in new primordia. Therefore, regulation of flower development by transcriptional master regulators and hormonal control of morphogenesis appear to be interacting processes. We found that hormone perception not only controls but is also controlled by the transcriptional signals that create plant form.