Plant process by which the shoot apical meristem changes its anatomy to generate a flower or inflorescence in lieu of new nodes with leaves. Anatomical changes begin at the edge of the meristem, generating first the outer whorls of the flower - the calyx and the corolla, and later the androecium and gynoecium.
Flower differentiation can take from only a few days (in annual plants) to 4–11 months (in fruit crops).
The process is preceded by flower induction.
References
Flower differentiation Wikipedia(Text) CC BY-SA