Passiflora is 'iffy' in zone 6. If you put a 8" deep layer of mulch around the roots, it will probably survive and re-grow in May or June.

I can do that. I always put down at least 6" anyhow - I have some mini roses not too far away, plus some hostas and other perennials. And I use plenty of compost and organic fertilizer (actually worm poo) from spring to fall. I just thought that maybe there was some nutrient that would/could make it stronger. Oh, well...

So, it sounds like if I treat it like any other tender plant, I at least have a good chance to keep it. Thank you! If it works, I'll add another one next spring, to the other side of the arbor.

But it does make the point that you can't believe Michigan Bulb, huh?

I live in northeastern Pennsylvania and have no problems growing passiflora caerulea. One planting is near my home's foundation(which probably bumps it up a zone) in dry, poor soil. Spreads ever year and blooms prolifically from June until frost without any amendments to the soil nor winter protection.
Also have it growing in a compost rich bed that I keep mulched with about 2" of bark chips. Does not bloom nor spread as well as the foundation planting, but does return every year.

Thanks, Valerie, that's interesting. I have some other plants that keep coming back no matter how "bad" the place they are in seem. What kind of sun does the foundation have?

Sunny from noon to 5 p.m.