The answer is that the author used the word willow to portray two different meanings by using the techniques of metaphor and personification.
''An old <u>willow</u> with hollow branches slowly swayed his few high tendrils and sang(...) >> Here the author used the technique of personification in order to explain that the branches performed the human action of dancing.
''Love is a young green <u>willow</u> (...)'' >> Here the author used the technique of metaphor to compare love to a green willow (Willows are associated with spirituality and the ability to bend without snapping, a methaphor that is commonly used in Celtic culture to teach that we must adjust to the situation/feeling instead of fighting against it)
