Dahlia “Royal Dahlietta Yellow” plants were grown in controlled temperature chambers under 25 different day and night temperature environments ranging from 10°C to 30°C. The day length was 12 hours with an average PPF level of 300 micromolm-2 s-1 at canopy level. Leaf unfolding rate, shoot elongation and flower development rate were determined and models developed. Leaf unfolding rate increased as temperature increased up to 25°C. Stem elongation increased as the difference between day and night temperature increased. Flower initiation was delayed at high (30°C) temperature and flower development rate increased as temperature increased from 10°C to 25°C. Plants are currently being grown under greenhouse conditions to provide data for validating the models.