IT is the season of catkins — and the irritating white stuff that floats in the air from the trees that can pose potential health risks.

Shanghai’s roads and streets are lined with about 1 million trees. It is the plane, poplar and willow trees that create catkins, which are typically downy, pendulous, composed of flowers and wind-pollinated.

The peak season for catkins is from April to mid May, according to Li Xiangmao of the Shanghai Greenery Management Station.

“Plane trees are the biggest producer of catkins, while poplar and willow trees are commonly found around residential complexes,” Li said.

There are about 400,000 plane trees in the city, or 40 percent of Shanghai’s planted trees.

Plane-tree lined Shaanxi Road S., Fuxing Road M. and Hengshan Road are among the worst hit in the city.

“Authorities have taken measures such as injecting a liquid agent into trees and trimming them to curb catkin production, but there is no effective way to completely stop them,” he said.

Residents suffer from coughing, sneezing and itching due to catkins. Those who are allergic to it are advised to wear masks.

Yang Yuxin, who lives on Dongfang Road in Pudong, is allergic to catkins.

“It is the most disturbing season for me ... I really hate those flying catkins,” she said.

“I wear masks if I have to go out. I coughed for a month once due to these catkins,” Yang told Shanghai Daily.