Moonflowers grown from seed on the back porch. Same family as morning glories, same long vines and enormous (but tissue-delicate) flowers, different body clocks. They only open after the sun goes down and bloom one night before shriveling. Also, magic: A lovely, light scent like that of no other flower I know and a crazy supernatural glow when beamed by moonlight.
(Photo taken one September evening, but they’re still going strong.)