Serge you should have asked!
Well I think if a man says petal to another man that would be rather risky unless you were that way inclined
No problem with saying it to a woman though.
However, this terminology is very rare in England that I am aware of and something I seem to say to people a lot, to show my appreciation and to be different.
Where it originates I don't know, maybe because my mother used to say when I was a girl, "mon petit chouchou" Which when I asked her was a small cabbage...I would have liked better to be a petal

However in trying to remember the spelling, it has come to my attention that "mon petit chouchou" means something else,
chou Ã* la crème so that's a relief! course it would have been nice that my mother had told me this, I have had complex ever since about being a small cabbage!