Here is a link to a list of the flowers http://www.edibleincredible.net/ go here then click on helpful hints click on #8 and thats it... Cool website there to... Hope this helped???
Good Luck And Happy Baking! 
The flower list on that site comes from CC...there's even a link at the bottom of the page.
http://www.cakecentral.com/article18.html
If you try to research this you will find that each list have a different set of flowers that are NOT to be used and those that can be 
In other words, what's on the NO list can also show up on another list as safe.
It certainly best to try to talk them out of fresh flowers.
And...........NEVER< ever put flower stems into a cake unless thay are covered w/floral taps &.or in a straw to protece the cake.
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