Passiflora incarnata
Note: I do not know if Passiflora incarnata applies to the white blooms, or only the purple version.
These pics are from previous years, but the Passions are in full blitz right now.
While some believe the fruit of the Passion flower stirs the passions of the standard kind, the Passion flower is not named for any
aphrodisiac effects--Rather it gained its name when Spanish explorers came to the new world and were startled by the bloom, and saw in it symbols from the Passion of the Christ.
Symbols include: three prongs (Trinity), five wounds, crown of thorns, robe of purple, and forty lashes. While I do not know if God works to communicate on such a level, I am content with the idea the the one who made the world ---and the Passion flower, entered into the world robed in flesh.
For a picture of an unusual Yellow Passion flower, see Marvin's wonderful nature site:
http://elmostreport.blogspot.com/2008/07/yellow-passionflower-passiflora-lutea.html