that makes me withhold immediate rejection of Petal. :-) Since flower and plant names have already achieved their own levels of perceived legitimacy, Petal wasn't too far of a leap for me to make.
Besides that, I like Pet- names. Petal sounds like the pet form of
Petrona or
Petula or something (though I'd envision it Petel, and at any rate I'm
way off on a digression).