I don't know if this is 100% correct and if it holds true all the time.
It is said if the petals on the big ruffly ones have a notch on the tip them they won't hang. I tried to find some photos to show this but all the real ruffly ones have their petals recurved back where I can't see the tips in my photos.
I guess the best way to describe it is at the tip of the petal it is less ruffly or there seems to be a piece of ruffle missing.
