Catkin: Catkin belongs to plant flowers. When the preface of poplar is about to mature, the catkins will fly all over the sky as soon as they crack. Spreading catkins everywhere in the street will cause environmental pollution. Therefore, street trees should be planted with male poplars instead of female poplars.
Spring is the mature period of Chinese white poplar capsule (fruit). After the capsule is cracked, the seeds float in the air with the help of white catkins, which is an important way of poplar propagation. Populus tomentosa is suitable for planting in Beijing and was once the main tree species for urban road greening in Beijing. With the growth of tree age, the fruit setting of Populus tomentosa increased, and the female flowers of Populus tomentosa in Beijing were not vigorous, and catkins easily fluttered with the wind, forming a landscape of catkins flying everywhere in Beijing in spring.