You need separate shapes. You won't get great results trying to pull off the blend and a fill with the same objects. Even adding additional fills via the Appearance Panel will work unexpectedly with blends.
I would create a shape of the entire petal, add a white fill to it, move it behind the line work, and group...
So, each pedal consists of a solid white shape under the line work. Therefor overlapping/stacking will hide what's behind any particular pedal and I don't need to worry about clipping masks.
Part of the issue you may find with clipping masks is they are localized, meaning they hide what's outside the defined mask shape for that group of objects, not what's behind the clipping mask everywhere on the artboard. So, while a clipping mask may hide the blend outside the overall pedal shape, it's going to still show pedals through one another unless you create a clipping mask on the underlying pedals to hide their blends where things overlap. In short.... clipping masks to do what you want would be nightmare and way, way, way more involved than merely using a solid filled shape.