iconography alert - "the song of wandering aengus"

While doing some research tonight for "To Some I Have Talked with by the Fire," I discovered that any reference to apple blossoms (in the hair of the "glimmering girl" from Wandering Aengus) should not be tied with alchemy. According to W.B. Yeats: Metaphysician as Dramatist by Heather C. Martin (1987, pg 75) apple blossoms from Aengus' (of the Tuatha Dé Danaan) "island of the young" (Tir na Nog ?) induce dreams of forgetfulness. These dreams of forgetfulness are appropriately referred to as Danaan dreams. I'm glad I stumbled across this because while it is clear that the apple trees are no stretch, any alchemical connection I mentally made with the apple blossoms just seemed somewhat contrived. Does the girl wearing these blossoms in her hair signify that the author wants to forget about her later in life, that he won't forget about her, or that the girl would have been forgotten by all others b/c she disappears in mist as if she had never existed? I will have to dwell on this for a bit.