Why do Xi 'an's trees float cotton in spring?

Growth characteristics of willow, poplar and buttonwood. It is a natural law that the hair on the tree will be blown off by the spring breeze in spring.

Catkin and poplars. Catkin and poplar are the seeds of willow and poplar. Willow and poplar choose to spread seeds around the wind direction in their evolution, so that their descendants can spread more widely.