Many plants flower in response to changes in day length. In Arabidopsis, long days induce expression of FLOWERING LOCUS T (FT) and the resulting protein is transported to the shoot apical meristem (SAM). Previous evidence suggests that, in the SAM, FT interacts with FD, a bZIP transcription factor, to initiate flower development by upregulating floral meristem genes, such as APETALA1 (AP1). However, FT-FD ‘florigen’ complex formation in the SAM has not yet been shown. Now, Mitsutomo Abe and colleagues use improved bimolecular fluorescence complementation (iBiFC) to identify FT-FD complex formation in the SAM, and they show that the complex and AP1 are colocalized in the floral anlagen. In addition, the authors use a heat-inducible improved bimolecular fluorescence complementation (iBiFC) assay to investigate FT-FD dynamics during floral transition. They reveal that the FT-FD complex cannot be detected in the SAM soon after the transition, likely because of repression of FD. The researchers also show that FD is necessary for the retention of FT in the nucleus and for FT-FD complex formation. Finally, they report that prolonged expression of FD causes abnormal flower development and reduced fertility. Taken together, these results suggest that the FT-FD complex is regulated by controlling FD expression and is required for a transient period for floral transition.