Jym, not too sure if that's a mirror there.
The sequence of the flowers over lapping each other does not seem the same.
Agree with Sion though.
Definately backlit with a soft light.
But to get back the slightly under exposed details of front of flower, a reflector might be used.
Or if it was not enough, maybe another soft light with 3-4 stops less output was used?
The shot was taken under backlit condition, and my guess is either with a softbox as others had suggested, or backlit under a bright sky. You can try the following to get the exposure (using the pic you posted as an example):
(1) spot meter the lowest petal of the white flower. This reading will give the value of the petal exposing as mid tone.
(2) compensate the reading by +1 to +1.5ev. For e.g. if the reading is f/8 1/500s, use an exposure of f/8 1/250s (for +1ev). You can bracket the shot.
(3) if the background is more then +2ev from the reading taken from (1), it will be overexposed and turn out white. Take care not to over do it, otherwise the backlight will bleed into the petals (e.g. you can use a relfector to brighten the flowers to bring it closer to the backlight).
hey u no... looking at that picture again... cudn't u say the flowers were made of a cloth-like material? it certainly looks real, but fakes these days look so real and maybe the material is translucent and with the techniques above u could get the same results? jus another one of them guesses... (Shrugs...)