[Gallowsraven]

Oh my gods! I know that poem! I read it in the Tripod Trilogy, it's in the first book because one of the characters is called by that name because he likes the character, or some such, it's a bit confusing and the story is set way into the future. I think.

"And the imperial votaress passed on,
In maiden meditation, fancy-free.
Yet marked I where the bolt of Cupid fell:
It fell upon a little western flower,
Before milk-white, now purple with love's wound,
And maidens call it Love-in-idleness."
~ Oberon to Puck in A Midsummer Night's Dream, explaining how the flower got its power.