In the spring with catkins all over the sky, please be careful of allergies

It is April again, the spring has come. After the snow has completely melted, another "snow" comes. This spring snow is all over the streets and alleys, and white fluff is piled up everywhere. These snowflakes are what we commonly call catkins or poplar catkins. But catkins, which symbolize spring, make people who are prone to allergies avoid them. But in fact, catkins can do more than just make people sneeze. Let's learn about the harm and prevention of catkins.

01

How are catkins produced?

Willow mainly refers to plants of the Salicaceae family, such as white poplar and weeping willow. Willow has a long history in my country. It was first recorded in the Book of Songs and is a common image in literary creation. Now, willow is a common street tree in northern my country. Because of its high survival rate, fast growth rate and low maintenance cost, it has been planted in large quantities since the 1960s and 1970s.

Willow trees in spring | Tuchong Creative

Botanically speaking, willow is a dioecious plant. Unlike the common flowering monoecious plants that have both pistils and stamens, a willow plant only has stamens or only pistils, so willows are divided into male and female plants.

After entering the reproductive maturity period, the male flowers on the male plants mature and the anthers naturally split open. The pollen is spread by wind to the female flowers of the female plants for fertilization. The fertilized eggs form fruits, and a large number of white fluffy hairs are contained in the fruits of the willow. The mature capsules gradually split open, and the white fluffy hairs carry the sesame-sized seeds of the willow and fly all over the sky with the wind, expanding the family, and the phenomenon of "willow flying catkins" appears.

Since willows carry out this reproduction process in a massive way every spring, cities that have planted a large number of female willows (such as Beijing, which has 284,000 trees planted in the urban area) can see quite spectacular "spring snow" every spring, which is beautiful but also brings great harm.

02

The willow catkins floating in the wind hide evil intentions

The specific hazards of willow catkins are as follows: First, willow catkins can spread germs and irritate the human body, causing allergies and inflammation, etc., thus posing a threat to human health; secondly, willow catkins can block vision and affect the heat dissipation of the car. At the same time, willow catkins are flammable and may cause fires, so they will also affect traffic safety and public safety; finally, willow catkins can affect the operation of some precision instruments, affecting industrial production and scientific research activities.

In order to investigate the impact of catkins on the environment, scientists in Beijing collected catkins from several parks in Beijing, washed them with simulated rainwater, and measured the content of lead and zinc in the water. They found that the content of heavy metal ions was higher than that of surface water, indicating that catkins have a certain enrichment effect on heavy metal ions. Since people can easily come into contact with catkins, safety in this regard should also be paid attention to.

The seemingly innocent catkins are actually a nuisance to the locals | Tuchong Creative

In April and May, when willows are in bloom, you can often see clusters of catkins, whether indoors or outdoors, in offices or at home. According to statistics, each willow tree can produce 25kg of catkins during the two-month flowering period. In Beijing, these catkins floating in the air can account for 2%-10% of the particulate matter in the air. These catkins carry a lot of dust and germs in the dust, which can cause people to cough, eye inflammation and various other allergic symptoms.

During these two months, we should stay away from catkins, because catkins are still very dirty. Especially for people with allergies, they must wear masks, try to avoid flying catkins, and clean up catkins on their bodies after returning home, so as to avoid being "infected" in Beijing in April and May. At the same time, we must not try to ignite the accumulated catkins out of curiosity, as catkins burn very quickly and can easily cause fires.

However, there are rumors that willow catkins floating in the air can actually carry the new coronavirus. Is this true? Although willow catkins can indeed carry some bacteria and dust, they are not a suitable carrier for the new coronavirus. There will not be too much new coronavirus attached to the catkins, and the new coronavirus cannot remain too active on the catkins. Therefore, under normal circumstances, the probability of willow catkins carrying the new coronavirus and causing infection with COVID-19 is extremely low (besides, there are masks).

03

There are many ways to block catkins

What measures do we have to curb the flying of catkins? The first method is the simplest, which is to spray water on the crown of the willow tree to suppress the catkins like suppressing dust, but the effect is not very good; the second method is to inject catkin inhibitors into the willow when the flower buds are formed (depending on factors such as light and temperature in different places), so that there will not be a large number of catkins in the next year. This method is very effective, but the cost is high, and if the injection method is not done properly, the willow may be infected and die.

Injecting drugs into trees is a common method of inhibiting diseases or protecting trees | Tuchong Creative

The third method is to cut off all the branches on the upper part of the willow plant when it is dormant in winter, leaving only the main trunk. This way, the willow will not grow reproductively for a few years, solving the catkin problem within a few years. However, this method has caused great damage to the beauty and greening effect of street trees, so it is only suitable for plants with extremely poor growth and difficult to maintain.

Although willow catkins are annoying, willows are the heroes who protect the land from being swallowed by wind and sand in the north, and they are irreplaceable at present. So why not be optimistic and prepare for the "spring snow" that comes every year?

Author: Xu Jiaxian, Biotechnology Major, Sun Yat-sen University

Review | Gu Yourong, PhD in Botany, Chinese Academy of Sciences, Associate Professor, School of Life Sciences, Capital Normal University

Editor | Jiang Fan

Editor | Ding Zong

References

1. Xiaoming Wan, Gaoquan Gu, Mei Lei, Weibin Zeng, Bioaccessibility of metals/metalloids in willow catkins collected in urbanparks of Beijing and their health risks to human beings, Science of The TotalEnvironment, Volume 717, 2020, 137240, ISSN 0048-9697,

2. Qi Songwei, Wang Xiujun, Ren Hanying, Zhang Lingfei, Mou Zhihui. A brief analysis of the prevention and control methods of willow catkins in urban gardens[J]. Journal of Agricultural Disaster Research, 2021, 11(08): 124-125+127.

3. Willow catkins carry the new coronavirus? Don’t believe these new coronavirus rumors! http://www.kepu.gov.cn/www/article/dtxw/e9f2b061e7a949e8a2c71b88f6e842e5

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