It is so hard to get photos of these flowers, because I have to keep an eye out to catch them blooming. The leaves that they spring from look very unsubstantial. They are white so that they can attract the sphinx moth, their pollinator.
Cereus supposedly blooms in the summer, but mine just recently bloomed because Florida's winter is freakishly hot this year. We make lots of jokes about it, but it is not natural and I don't appreciate having to pull weeds in the off-season.