Because its flower buds have been formed slowly in the autumn of the previous year. After experiencing the environmental changes from hot to cold, the flower buds begin to differentiate. Therefore, when the spring comes, when the climate warms up, the flower buds begin to bloom. However, the requirements of leaf bud and flower bud germination are different. The requirements of leaf bud germination on temperature are high, so it will bloom first, and germinate leaves after the temperature rises.
