No difference. There is no difference between the emperor's cabbage and Chrysanthemum coronarium, they are the same kind of vegetable, only the emperor's cabbage is the alias of Chrysanthemum coronarium. Because in ancient times, Chrysanthemum coronarium is specially dedicated to the emperor to eat the tribute, so called the emperor vegetable. In most parts of China are planted, and can be used to make dishes, drinks or various foods.