Abstract: The first flowering time, changes of p lant height, crown diameter, branch number, and flower number of Petunia hybrida ‘Fantasy Pink’cultivated separately in long days and short days were recorded. Seedlings of petunia ‘Fantasy Pink’were transferred from short days to long days upon reaching 2, 4, 6, 8, 10, 12, 14, and 16 leaf stages respectively, the time from transfer to first floweringwere measured. It is concluded that petunia ‘Fantasy Pink’ tends to have an up right habit under long days and a compact habit under
short days; petunia ‘Fantasy Pink’ is a quantitative long day plant; it should be more vegetatively developed before flowering under short days; and the end of the juvenile phase of petunia ‘Fantasy Pink’ is 8-leaf stage. Primary suggestion was p resented that petunia ‘Fantasy Pink’planted under short days before 8-leaf stage to be compacted in morphology, and then under long days to be fast in flowering.

Key words: Petunia hybrida, Photoperiod, Morphology, Juvenility, Leaf