willow: it refers to the willow song. In ancient poetry, the willow tree is often used as a metaphor for farewell.
The original
The Yellow River is far above the white clouds, and it is a lonely city, Wan Ren Mountain, written by Wang Zhihuan in the Tang Dynasty.
why should Qiangdi blame the willow? The spring breeze doesn't pass Yumenguan.
Translation
The Yellow River seems to be rushing from the white clouds, and Yumenguan stands alone in the mountains.
why use the Qiang flute to play the plaintive "Yangliuqiu" to complain about the delay in spring? It turns out that the spring breeze can't blow around Yumenguan!