Why did the ancients fold willows to bid farewell?

The word "folding willow" means "Farewell to the distant future". In ancient China, once relatives and friends were separated, people who saw them off always gave them a wicker as a gift for travelers. This was a very popular folk custom at that time, especially among literati, and it became a fashion. China's custom of "folding willows to bid farewell" was first seen in China's first collection of poems, Xiaoya. Cai Wei: "I have been there, Yangliuyiyi; When I think about it today, it's raining heavily. In ancient times, willow was also called Xiao Yang or willow. Because "Liu" and "Liu" are homophonic, they can express the meaning of retaining. Farewell to willow means inseparable, reluctant to part, such as Yu's Folding Willow, "Flowers in tears send farewell to the DPRK, all willow smoke is folded", "Folding willow to bid farewell" and Li Bai's "Climbing the pole to fold the spring scenery and send it far to Long Ting"; Li Bai's "Xuancheng sent Wei Liu's deputy envoy to Qin" and "No Sauvignon Blanc, No Break" all expressed this idea.