Paul, There are 500+ passiflora. Some grow in specific environments .Most are tender but are easily overwintered in greenhouses. I trim the vines and lift them from the ground.I keep them in plastic 12" pots, alittle dry over winter. You could let in P incarnata and P. caerulea overwinter in the ground in zone 7. Type Passiflora Society in google and check out the beautiful sites from all over the world. Most have English language selections.
Some seeds are easy but most are not.
Flicker

Hi Paul,
I have some Passiflora 'Incarnata' plants growing in my pasture that I'll send you. Most nonhardy passionflowers are cheap enough and grow so large here in the ground that they're worth treating them as annuals. Buy a couple of varieties (or trade for them) and enjoy them as annuals. :-)
Dawna

I find that the older the vine gets, the more flowers it produces. It is worth digging them to overwinter in a greenhouse.

Passiflora lutea is also hardy in z7.