Your problem might actually be the opposite of what you suspect. Passiflora, by and large, have evolved to grow in poor soil conditions. In many cases, fertilizer only encourages aggressive vegetative growth and inhibits flowering.

It might help if you let us know what types of passis you have in pots. For the most part, passis like it hot and humid, and many species flourish in Z8.

I'm having the same problem with my large 'frederick' and quad. passi's. They are in containers as well, and I don't fertilize.

Amanda 'romando'

Passiflora edulis var. "frederick" is a heavy feeder, and I cant get mine to stop flowering in zone 10, whether it is the ones in the ground or in pots. A balance time release fertilizer works well, but be awarare that over fertilization and wet roots will produce root rot. They also are easily stunted by small pots. A 3 gallon pot may only produce a four to six foot plant and a dozen fruit in a year. You might also try a foliar spray, to restore micronutrients.