Hi, I'm new at pasiflora's but not flowers :)..You want high potassium for best blooms. Also from what I've been reading about passie's almost everything says the same thing high potash. I would use something along the lines of rose food (mine has high potash) or azalea most that are meant for flowering plants usually have high potash. HTH
Anela

Any high bloom yield fertilizer should work.