Abstract: From investigation of the development of pollen grains combined with flower growth, the inflorescence development in Wedelia trilobata was divided into 7 phases, from P1 to P7. The growth of ray and disc florets was determined during inflorescence development. Ray florets elongated faster than disc florets from phase P3, when tetrads of haploid microspores appeared, and the pigmentation of the ray floret began when the pollen grains showed germination apertures in the disc florets of the first whorl. The effects of light, sugar and GA3 on flower growth and development were investigated in vitro. Inflorescences in the P2 phase or later could grow and bloom in vitro, and sucrose, GA3 and light promoted flowering.