Hopefully someone will jump on to respond to my negative view of growing from seeds.

I've personally only grown a couple plants from seed, and none of those to bloom, so I'm not the best person to answer this question. I would really recommend starting with cuttings, and better yet rooted cuttings. Unless you are someone who truly enjoys growing plants from seeds, it can be slow and frustrating. For some rare species, it's necessary and for creating new hybrids it's necessary. I suppose it's good to have a genetically diverse population of plants, but for most people this is not relevant. If you already have seeds, of course, by all means try.

Soaking in orange juice is often recommended, giving enough time (I'm not even sure--a couple days??) to get some fermentation. Do not abrade the seeds--you will only damage them by doing that. I would plant them shallower than you suggest--I think one or two depths of the seed should be appropriate. And then you have to be patient. Depending on the species, the age of the seeds and other factors, expect germination to take anywhere from a week to a year. You really have to be patient. I doubt you will be able to outgrow a 1 gallon pot this season.

You will have to bring everything inside in your zone, before frost. You may be able to plant P. caerulea in the ground next year and take whatever steps people do to protect plants in the winter. Even then you are probably borderline in your zone for growing them outside. I think there are discussions online as to whether that species can be grown outside successfully in your zone.

I would guess 1-3 years until you see those bloom. Maybe P. caerulea will bloom in less than a year?? Few people, even in favorable climates, can bloom P. edulis in under 1 year. I am less familiar with P. alata, although since it is such a big plant I would assume it takes a while. Regardless, if anything blooms this summer I would be surprised. If you are really looking for quick blooms, I understand P. foetida can be quick. Maybe also P. incarnata is fairly quick. I'm sure there are others.

I'm sort of curious about the 80% germination rate. Did someone sell you the seeds and claim this? Is this from a (recent) germination test? The reason that I ask is that a lot of non-viable or old or slowly germinating seeds are sold. My experience with seeds is that either none germinate, or almost all, or just a few. A consistent 80% for three different species seems odd.

I should add that I generally try to avoid growing plants of all sorts from seed when possible. Still, Passiflora can be among the most frustrating and the plants are generally easily grown from cuttings.

I do already have the seeds, and the only way I know the germination rate is because it was given on the front of the package; Alta 82%, Caerulea 80%, Edulis 78%, but who knows how realistic those are.

Soaking in orange juice makes sense and is a really good idea, thanks for that tip. Good to know they can planted in pots, will be a bit more manageable with other projects I have planned.

Still curious if they die off from the snow/frost, will they be gone forever or will they grow back come spring?

I've heard that passiflora's can be difficult, but I don't really know where to get anything other than seeds, unless there is a viable option to acquire cuttings online?

Thanks, I appreciate all the help.

I don't mean to discourage you from planting seeds you already have. You should just be aware that germination can be slow and they may take a while to bloom. A lot of nonviable seeds are sold as well. I would believe the germination rate if they tested it themselves in the last couple weeks (very, very few seed sources do this). Even then seeds can lose viability quickly.

All of those will be killed off by frost/freeze. I think I've seen P. alata given as surviving 30 F, P. edulis is usually somewhere in the 20s, maybe around 30 or 32 for P. edulis flavicarpa. These are all numbers for plants in the ground. Some can come back from the roots. In pots, I think you should assume they would die around 32, and protect them from all frost.

P. caerulea is more hardy. I'm not sure at what temp it will die back to the ground (20s?). If it is in the ground, it came come back from the roots in colder climates, probably zone 7, maybe colder with some luck, mulching, etc. As I say, I think you are borderline--for growing it in the ground. In a pot I would keep it above freezing.

All three of those species are rapidly growing vines, especially when planted in the ground. Cutting back any of those generates a tremendous number of cuttings. A lot of cuttings end up in the trash or composted. I don't grow any of those at the moment, and only have a couple small Passifloras right now due to a move. I may have something rooted in a couple months, possibly P. caerulea, but not the other two. My general problem is that I tend to grow the cool-growing plants that don't like the heat (or cold) of the rest of the country.

You can find rooted (and generally potted) cuttings on Ebay or at online nurseries such as Grassy Knoll, etc. They will cost more than seeds, but if you get them from a good place they are closer to a sure thing, and it often puts you ahead by as much as a year. Of course, it's the only way to propagate a hybrid.

You might be able to find unrooted cuttings rarely on a place like Ebay or sometimes for trade or for postage. In this case, things need to be good on both ends--the person needs to send properly prepared/shipped cuttings, and the person receiving them needs to be good at rooting cuttings. Sometimes the weather in transit or the post office can be a problem. Some species/hybrids should be easy, but there are more things that can go wrong.

By the way, if you see a P. edulis for sale and they have a photo, the plants with unlobed leaves are seedlings (or misidentified). I think a rooted cutting might be quicker to bloom than a seedling of the same size.

All three of those should be easy or fairly easy to propagate from cuttings. P. edulis might be the hardest, and I find they are much easier with bottom heat. Some people find P. edulis to be easy regardless.

Are there any passiflora strains that would be able to die off in the winter and grow back in the spring?

I'm not too concerned with the exact type of passiflora right now, so any other P. xyx... I'd be interested in growing, any input from someone growing them would be great.
Buying cuttings and rooted plants off a website stay viable through shipping and live healthy on arrival? I was very skeptical of this, I'd prefer seeds, but if this is the only way I'd rather not throw money away...

Your best bets for surviving the winter would be strains of either P. lutea or P. incarnata that are naturally from the Northern range of these species and/or known to survive winters in zone 5 or zone 6. Both species are native over a wide range of the Eastern U.S. Strains that originate from Florida are probably not what you are looking for.

P. lutea is less frequently grown than P. incarnata and has smaller flowers. I think your best bet would be to locate someone in zone 5 or 6 who successfully grows P. incarnata outside. I understand this plant is most easily grown from suckers which appear in Spring (apparently the vine can return surprisingly late--even June in some places). Apparently it is often difficult to root cuttings of P. incarnata. Seeds are an option, although I gather a lot of inviable seeds are sold. So, make sure your source has fresh, viable seeds.

Many people find P. incarnata to be invasive (since it spreads by suckers). I don't know if this would be true in your zone.

Again, P. caerulea might make it... I'm not sure about P. incarnata hybrids such as P. 'Incense'.

A good commercial source should be able to send you a plant in a pot that should survive shipping. Rooted cuttings should be OK if they don't get frozen or overheated at some stage. If they are bare-root they can even travel in an envelope if everything else is favorable. Unrooted cuttings can be sent of most things if people on both ends know how to deal with them. Some things, generally the cool growing (high elevation) species, I think, seem to be more problematic. Generally if you pay for cuttings they are rooted and in pots.

One rooted cutting shipped in a pot of course costs as much as a lot of seeds. So if your goal is to do it cheaply, try seeds. If you really want something to survive the winter, than you should specifically find a variety of P. incarnata that has been shown to survive in your zone or colder. This is true whether you grow from seeds or from a sucker with roots, of course.

Here is a link that might be useful: Maps showing native range for P. incarnata, P. lutea, etc.

I've grown a number of passiflora from seed and get blooms on just about all unless I lose the plant early on. Some have taken a few years to produce flowers but most have bloomed their second summer. A few varieties bloom the first year from seed for me.

I sometimes soak stored seed in a mild acid like orange juice for 2-3 days before sowing. When starting the seeds inside I use bottom heat. Make sure that the soil isn't kept too moist or they'll rot. Passiflora seeds have really erratic germination rates. I've had seeds from the same fruit come up months apart. Some only take a couple weeks to sprout and others can take at least 6 months. It takes a long time before I give up on seeds. I have a number of plants growing in recycled soil with volunteer passifloras popping up.

I wouldn't plant any of those passifloras directly in the ground in your zone. The only one that has a chance of surviving a zone 6 winter is the caerulea. I'm in zone 7a and caerulea doesn't always survive the winter here when left inground. P alata is a zone 9 plant and edulis zone 8. There's no chance on God's green earth that either variety can withstand a winter in zone 6, even with a foot of mulch. It would be a waste of time to start new seeds every year as they might take a while to get buds. You can sink a plastic nursery pot in the garden during your growing season and lift it before the first frost and keep the plants going inside. You can cut them way back so they aren't taking up a load of space. They should be cut back anyway since you'll be removing a good deal of the root system when you lift them.