Dahlia, also known as Dahlia, Tianzhu Peony, Sweet Potato Flower, Dali Flower, Passion Flower and Chrysanthemum, is a perennial herb in Compositae. Chrysanthemums are in full bloom in Ao Shuang, but dahlias are different. It blooms in spring and summer, blooms again in Xia Hou and withers in the first frost. Its flowers are similar to the beautiful peony in that country, and the colors are magnificent and colorful, which makes people fondle it. Dahlia is the national flower of Mexico, the provincial flower of Jilin Province and the city flower of Zhangjiakou City, Hebei Province. Colorful dahlias symbolize generosity, abundance and good luck. It has traveled all over the world, becoming a frequent visitor in gardens and a world-famous ornamental flower.