What is the symbolism of the yew tree in Plath's poem, The Moon and the Yew Tree?

Within certain European Christian traditions, branches of yew trees are displayed at Palm Sunday. In adjacent cultural traditions the yew tree was seen as a symbol of death or mourning as well as a symbol of infinity or immortality. This gives the evergreen tree a connotation in the poem associated with the solemnity of religious rite and imbues it as a symbol of the despair and despondency attached to mourning.