This is 柳(liǔ; willow tree). There are a lot of 柳 in old poems in Asia, because the trees are distributed in all around the Asia and europe. The tree likes water so they are usually near the watersides.
Willow trees are regarded as 陽, yes 陰陽; Yin and Yang that yang, so it was even used for exorcism. Leaves and barks are used as medicine for its anti-inflammatory. It is also used for a farewell gift, because the sound of 柳(liǔ; willow tree) and 留(liú; stay, keep) the same.
It has very distinctive flowers which look like cotton puff then it sheds fluffy pollens, it is called 柳絮(liǔ xù), here 絮 means pollen becase the pollen looks like these👇
They are like cotton fluffs. So basically Wen kexing is keep caling Zhou zishu, baby fluff. His baby fluff 🤭
