古人所稱「楊柳」，多指「柳樹」而非「楊樹」，二者在現代植物學分類上同科而不同屬。古詩詞中常以「楊」或「楊柳」稱代「柳」；「楊花」也多指「柳絮」楊柳科柳屬植物因爲易於栽植且生長快速；柳蔭可以乘涼與美化環境；柳條可以編製筐笥籃簍；枝幹可供柴薪；柳根可以護堤固岸，因此長城內外、大江南北都廣為種植，留下不少垂柳夾路，柳岸成蔭的古道。物用功能之外，楊柳在民俗觀念上被視爲有避邪之效，於是有插柳、戴柳之俗；在精神層面，折柳是贈別懷遠的象徵，射柳的競技更是古代一種軍中遊戲；楊柳柔條低垂的外型特徵與易於阡插繁殖的生長特質，也常引人聯想而衍生許多形容譬喻。至於楊屬植物，除樹材可供器用，也是華中華北地區常見行道樹，葉形較大且枝條勁揚，風吹葉動窸窣作響，落葉時節更有蒼涼之感而屢見用於詩文蕭瑟氛圍的描寫。基於這些物象觀察與民俗文化的積澱，表現在文學作品與生活情境中也從而形成一種譬喻、借代修辭或象徵意象。因此，明瞭「楊」「柳」名類之別與歷來種植情形、功能用途及所衍生之民俗事項，應有助於對楊柳意象之情境氛圍與其形成背景的理解和掌握。

Poplars and willows always came together in a Chinese phrase in the past while this phrase mostly referred to willow instead of poplars. Botanically, poplars and willows belong to the same family but different genera. Poplars or poplars and willows often represented willows in classic Chinese poetry; also poplars flowers mostly referred to willows catkins. Plants belong to the genus Salix within the family Salicaceae are easily grown and fast-growing. It feels relaxed to have a rest under the shade of willows and willows can also make the environment greener. The branch of willows can be used to make baskets, and the trunk of willows can be firewood. Furthermore, the root of willows can enhance the stability of the riverbank so willows are widely planted outside and inside the Great Wall. Willows on both sides of the road or willows shade covering the road are commonly seen. In addition to its functions, willows are taken as something that can ward off evils in folk custom so people plant willows and wear willow-made things as a convention. Spiritually, breaking a branch of willows represents farewell and memory. The Willow Shooting Contest was a game widely played in the army while the soft and weeping appearance of willows as well as their easily-growing characteristic leads to many relevant descriptions, metaphors and similes. Ancient people often made the trunks of poplars into containers while such plans have also been widely seen on the sidewalks in the central northern parts of China. With larger leaves and strong branches, poplars make sounds when blown by the wind; furthermore, the desolate and bleak feeling it represents when leaves fall has often been described in poetries to present similar atmosphere. Based on poets' observation and the cultures and customs of China, these descriptions have become common rhetoric in literary works, representing a type of metaphor, simile and symbol. Therefore, having a clear understanding of the differences between the words "poplars" and "willows", the way of planting them, relevant customs and cultures as well as the atmosphere presented by these 2 plants enables people to understand the imagery described through these plants in literary works.