Willows and poplar trees produce catkins in late spring to spread their seeds. In Xi'an City, northwest China's Shaanxi Province, catkins can be seen everywhere.

They look like cotton balls with seeds wrapped in fabric. While blowing about, the catkin seeds fall to the ground, where they will germinate and become new trees.

Though willows and poplars are both beautiful ornamental trees, their catkins have become somewhat of a menace. During spring, too many catkins can increase the risk of fire as they are very flammable. The floating catkins can also affect the air quality. They are also a nuisance for urban residents who are allergic.

(Video recorded and edited by CGTN's Xu Chenlu)

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