EDIT Hope this dont confuse you dear -- yes and also as term of light endearment well mostly, it can be used somewhat condescendingly [link] but mostly if someone calls you "petal" they are being more sweet to you (But sometimes in a condescending way)
on of those tricky ones where you need to know them and the context before the use of the word..
so for example
non condescending would be "your a sweetheart & I love you" petal
condescending. would be I love you sweetie but your being a bit dumb" ...or something along those lines
So a multi purpose word dear.. (one of emotion..which I guess flower bring to us)