Speed breeding has recently emerged as an innovative agricultural technology solution to meet the ever-increasing global food demand. In speed breeding, typically various light qualities (e.g., colour, duration, intensity) are modified to manipulate the circadian clock of the plants, which in turn alter the plant growth and enhance the productivity such as by reducing the flowering time. In order to develop a comprehensive framework describing plant growth, a model incorporating the effect of various light qualities on plant growth needs to be established. Recently a mathematical model of the plant circadian clock for Arabidopsis thaliana has been developed to characterise the hypocotyl growth subject to multiple light quality properties. This is a first step towards developing a more comprehensive model that links light quality, plant circadian clock and plant growth. In this work, we extend the model by adding the effect of various light qualities on the flowering time. The proposed model can capture the flowering time behaviours of plant when subject to red, blue, and mixed lights and can be used to guide experiment of light properties manipulation for optimised plant growth via hypocotyl growth and flowering time.