From Ask Kit:
Q: Do you know anything about edible flowers for use on wedding cakes? I have weddings booked and plan to do the cakes—I have done them before but I am looking for something more elaborate.
A: There are lots of great edible flowers to use for decorating cakes. Let me share the ones I have found.
* rose petals
* English cowslips
* violets — if they are very freshly opened
And of course you can make crystallized flowers to use too.
Enjoy, and let us know how it came out!