For awhile now I've been considering these for our wedding. I found Fly Boy Naturals when I was doing research for hydrangea petals. They carry rose, peony, hydrangea and some lilac petals all freeze dried. Since they are natural they still break down (instead of confetti or silk petals) and don't leave an impact on an outdoor space. They've been featured in a variety of bridal magazines as well as the today show and carry a variety of color and price options. I love the blue and green hydrangea petals.
I may get some for our guests to toss after the ceremony. I'll need to do a bit more research still though. If anyone has used freeze dried petals or have any more info on them, I'd love to learn more!