A flower development stage (PO:0007615) which begins with the transition of a portion of meristem tissue (PO:0009013) to a flower meristem (PO:0000229) and ends with the onset of the floral organ formation stage (PO:0025585).

During this stage, a process occurs involving a vegetative to reproductive phase transition of meristem (GO:0010228), defined as the process involved in transforming a meristem that produces vegetative structures, such as leaves, into a meristem that produces reproductive structures, such as a flower or an inflorescence.