Willow, a kind of plant, refers to willow, which comes from China's ancient poems. Originally from the Book of Songs: "I have been there, Liu Yiyi. I came today and it rained. " Willow originally means willow, because in spring, willow can fly, which easily causes the sadness of the ancients. When reading these poems, many people may think that the "willow" mentioned in these poems is both poplar and willow, but it is not. The "willow" in these poems refers to willow, which has nothing to do with poplar mentioned in modern botanical classification.