The ancients often used willows to express feelings of parting.
Tips
culture
In classical Chinese poetry, 杨柳 is a powerful symbol of parting — 柳 (liǔ) puns on 留 (liú, 'to stay'), so snapping a willow branch (折柳) to give a departing friend was a way of asking them to remain.
memory
Both 杨 (poplar) and 柳 (willow) have the 木 wood radical — picture two kinds of tree whose drooping branches always get lumped together by the riverbank.
