Zinnia is a very attractive and beautiful ornamental plant due to the diversity of color and flowering period. The effect of cycocel and pot size was studied on growth and flowering of zinnia in a factorial experiment based on a randomized complete design with two factors: cycocel at 3 levels (0, 1000 and 2000 ppm) and pot size at 4 levels (10, 12, 14 and 16 cm) with 12 treatments and 3 replications. The interaction results showed that cycocel and pot size had a significant effect on all studied traits, that 2000 ppm cycocel in 12 cm pots produced the minimum height and that 16 cm pots treated with 1000 ppm cycocel or without cycocel treatment produced the maximum plant height. Maximum flowering period was related to 14 cm pots × 1000 ppm cycocel that had no significant difference with plants in 16 cm pot size in all three concentrations of cycocel. Minimum flowering period was related to 10 cm pot size at all three concentrations of cycocel. Zinnias planted in 10 cm pot size without cycocel treatment exhibited the minimum fresh weight and in 14 cm pot size without cycocel treatment exhibited the maximum root fresh weight. Overall, flowers in 14 and 16 cm pot sizes treated with 1000 ppm cycocel were found to be the best treatments. پرونده مقاله