Driven mad by his mother’s insane love for him, he castrated himself under a pine-tree. The pine-tree played an important part in his cult; every year a pine-tree was decked with garlands, an efhgy of Attis was hung upon it and then it was cut down.
Jung establishes the pine as the definitive cultic tree of Attis, the site of self-castration and annual sacrificial ritual, directly symbolizing the surrender of instinctual libido to the Great Mother.
, Symbols of Transformation, 1952thesis