“Lily had picked up a fallen flower from the bush behind which Snape lurked. Petunia advanced, evidently torn between curiosity and disapproval. Lily waited until Petunia was near enough to have a clear view, then held out her palm. The flower sat there, opening and closing its petals, like some bizarre, many-lipped oyster.”
-Harry Potter and the Deathly Hallows; chapter 33, The Prince’s Tale.