The rule of thumb to plant anything in a container that will live outside year round is to select from plants winter hardy to at least 2 zones lower than yours. And even that is not a guarantee. So you are looking at zone 3 plants and there are very few flowering vine that will fit that description........even most clematis will not tolerate that degree of cold.

So your friend will probably need to either plant something that can be brought in for winter protection or an annual vine(s). TBH, annuals make a great deal of sense. They will bloom heavily during the growing season and grow fast when needing to be replaced every year. And their appearance - or lack of it - in winter is not going to be much different from a dead looking clematis, honeysuckle or climbing hydrangea :-)

Climbing hydrangea laughs at any 10 foot limitation- way too large for a container plant/trellis situation.

I'd suggest a small clematis of some sort, just make sure it is a cold hardy variety.

Containers do not enjoy the insulating properties of being surrounded by soil so you usually subtract a zone or two to cover that.

Choosing a variety will take some thought, but here's one thread on cold hardy clematis and here's another. I'm sure the search function would turn up more.

I live in Zone5 Colorado (low humidity, so somewhat different than your friend. I do grow some clematis in containers. However, they die back almost completely during the winter and start all over again each year. So I could never expect that it will be 10 feet high and at least six feet wide ever.

Morning Glory does really well in a container and gets very tall maybe not 6' wide though. But it has to be replanted every year or let it seed itself.

@gardengal48 (PNW Z8/9) What are some annuals you could recommend that have a chance at filling a wall with vines and flowers?

@gardengal48 (PNW Z8/9) Which of those would likely take if planted from seed? I'm trying to avoid an expensive trip through customs for a live plant, if possible.

They should all start easily from seed, although some will germinate and grow faster than others. And it's getting a tad late into the season to be starting from seed so I would encourage your friend not to delay.

@gardengal48 (PNW Z8/9) I guess all of these will take normal potting soil and will want to stay moist?

Growing each species in a separate pot using something like a tomato cage as a trellis is probably a cheap/easy way to grow them out?

To choose an annual vine the summer temperature and amount of sun are important to know. For example runner beans do very well in my cool summers but T alata and some of the others mentioned might struggle except in a vey good summer. Morning glories can spend a lot of the their time shut under cloudy skies.

Is there a reason we can’t know the location to get a better idea of conditions?

Floral, my summers are pretty cool as well and not always consistently sunny :-) But the thunbergia and the firecracker vine have done very well for me. In fact, If I was to pick my personal favorite for a long and heavy bloom season, it would be the thunbergia. And I quite like the color choices :-))

westes, I grow my annual vines on narrow but tallish metal trellises or on teepees made from bamboo poles. The beans will fully cover those and then some but the others are not as massive. And I wouldn't mix the species. Pick one you like and go with that in multiples.

@floral_uk z.8/9 SW UK She is in the foothills above Almaty Kazakhstan. You aren't going to find any good reference for that. It's the literal definition of nowhere. It's quite beautiful, but its completely unpopulated and without references. If she lived in Almaty proper I would have better orientation.

@gardengal48 (PNW Z8/9) The three I want to try are:

Rhodochiton atrosanguineum "Purple Bell Vine"

Thunbergia alata "Black-eyed Susan Vine"

Ipomoea purpurea "Morning glory"

It is late to be starting on these so should I be looking for a well-developed plant in a nursery? I understand that Purple Bell Vine is particularly hard to grow from seed.

Now we know the location it should be plenty sunny enough and there seem to be plenty of nurseries in Almaty if that is the nearest large town.

@gardengal48 (PNW Z8/9) How big should the containers be for the three vines I selected? I assume something like 17 to 23 inches? Forming a 10-foot high teepee alone probably requires at least a 17-inch pot.