Bushes that Get Deflowered Nightly

I'm not sure what these are, I am not educated in such things, yet.   Apparently whomever owned my house before us knew something about tropical landscaping because these are all around the back yard around the pool area.   

They only seem to last a day (maybe a little more).

Maybe I'll call them by their scientific name...  Flowers.

UPDATE: One of my smart friends on Flickr has informed me these are Oleanders and are poisonous. Good to know!