I bought some 'hardy' Passiflora seeds last year.
The only two really hardy ones i saw in catalogs were:
Blue Passionflower and Maypop.
Only got 1 Maypop of 10 seeds to grow, and got 5 Blue ones.
I took in the Blue Passionflower and Maypop in the past few days (its like 11F-15F past week), was pretty surprised the Blue passionflower still had its leaves green, strongly attached, and not withered on the plant. Seems to be more cold hardy than the Maypop for me. Thought Passionflower would have "top growth is killed back by frost, but your Passion Flower will pop back to life in the Spring."... Well we've had a few 25F days before this week and its still loling alive... Mind you its not mulched, and all 5 Blue plants shared a 2gallon pot. So i assume the pot is pretty cold/frozen, yet this thing is still kickin' lol? The Maypop had all its leaves turn yellow and fall off months ago and the vine looks more yellow than green.