The experiment was carried out to clarify the effect of temperature on colouring of petals in Aster spathulifolius Maxim., 'Pink' strain. Plants with flowers were grown at 25, 20 and 15℃ constant temperature in a phytotron, Biotron Institute, Kyushu University. At 25℃ the colour of young petals were pink. The petals getting older, the colour faded and became pale greenish yellow. At 20℃ it was light pink and faded gradually. At 15℃ it was white. Thus the higher the temperature was, the more remarkable the colouring of petals and the change of the colour were.