Every external quality character in chrysanthemum is influenced by the growing conditions. In general, a good carbohydrate status is a basic condition to guarantee high external quality of chrysanthemum. For instance, chrysanthemum growing under high light intensity, higher CO2 concentration or lower plant density results in taller plants, with greater stem diameter and more lateral branches. Leaf thickness is also increased as well as flower number and size. However, time to flowering in chrysanthemum does not respond to CO2 enrichment but decreases with higher daily light integral. Temperature also plays an important role in chrysanthemum external quality. The optimum temperature is cultivar dependent and differs according to the stage of development.