Describe symbolism in The Mystery by Louise Gluck

Glück acknowledges that she wrote all the poems collected in Vita Nova at a rapid pace, completing a draft of the entire manuscript in only three weeks. She has said that they were written in hotel rooms and elevators, on airplanes, and while she was visiting friends in California. Apparently, "The Mystery" was written in her friend's "driveway in California" where yellow roses bloom nearby. The first stanza is full of references to the bright color, which symbolizes the "light" she feels she has entered into.