Well, I looked up the Jackmanii and it's supposed to be hardy to zone 3. If you cut it to the ground and cover the soil with mulch it'll probably be fine right where it is--maybe wrap the pot in bubble wrap so the roots don't freeze. The firs should also have no trouble dealing with the cold if you treat them similarly.

The boxwood, I don't know. Most boxwoods are not very cold-hardy and if you bring it indoors the lack of humidity will probably make it very unhappy. Anybody else have any ideas?

Mulch, suggested above, is an excellent idea. My container plants, assorted perennials, are out 7x24. All are well mulched, two plus inches. It sounds like you need a wind break too, (e.g., decorative panels tied with wire to your balcony, bamboo curtains firmly attached top and bottom). With a windbreak some of the wind passes through but most does not do so; this allows the windbreak to survive being destroyed or removed by the wind. Good luck.

Ditto the suggestions for the clematis. All the info I've read on the clematis forum is the same.

Re: the boxwood - I'm glad I happened upon this thread, I have 3 boxwood and I didn't know they weren't cold hardy!

Depends on what type of boxwood you have - some are not cold-hardy (to zone 8) and some are (to zone 5). As said above, a good covering of mulch is an excellent idea for everything. A windbreak is good, and you might want to spray them with Wilt-Pruf too, to help protect against moisture loss. Sometimes, folks wrap the pots in bubble wrap to help provide some protection to the roots.

Clematis are very cold hardy - mine have survived some pretty cold winters with no problem. Your Jackmanii is a type-3 clematis; it blooms both on last year's wood and this year's wood. If it's a young plant, you should just mulch and leave it alone - don't cut it back yet. You can cut off the obviously dead wood, but wait until leaves sprout in the spring. Sometimes the dead-looking vines aren't dead. If it's a more established/mature plant, you can cut it back drastically - in late winter or early spring. Cut it back to about a foot or two above the ground, above a nice healthy bud.

Whatever you do, mulch, mulch, mulch. And don't forget ot give a little water too - if the temps get above 40°F, give 'em a small drink.

PV

Actually, jackmanii blooms only on this year's wood. I've grown one in an old pickle crock on my 6th floor balcony in almost total shade for the last five years. It's pretty sheltered from the wind, though it does get some. I mulch both summer and winter with about 2" of shredded pine bark. In March I prune back to about 18" which encourages new shoots. It blooms well for being in the shade. Just don't let it dry out in the winter, although that's less likely where you live.

Here is a link that might be useful: Encyclopedia of Vines - Jackmanii Clematis

I'm new to all this but trying to do pretty much the same as you. In Toronto we can get night time temps as low as -27ish C.

My balcony is a concrete bunker style, 8' x 20'. My mugo pine and the boxwood didn¡¦t make it thru last winter. Not sure which type of boxwood it was. Have been told by others more knowledgable that even if I get them through a winter or two, they¡¦ll soon give up the ghost. That hasn¡¦t stopped me from trying. This year I have an Alberta Spruce and two cedars.

I repotted, watered and mulched them before the winter set in. I'll repot again in the spring and 'feed' them at that time.

I get the impression that layering, just like clothing ourselves, is a key principle, along with insulating plants from the freeze-thaw cycle. I've put the Alberta spruce inside a cardboard box in the hopes of cutting the wind and then wrapped it in a nice green coloured burlap, partly for appearance sake.

Some people I've consulted warned me away from bubble wrap because it could get too warm on sunny days and only excacerbate the freeze-thaw cycle you're trying to protect against. Nevertheless, I have used on some of my plants this winter.

I'm usually told to keep the plants away from the sunny part of the balcony so that on warm days they don't warm up too much.

I've been tempted to bring one of my cedars indoors just to see whether it would in fact die from being indoors. The daytime temperature in my unit is usually about 18C without putting any heat on at all so I don't. I almost always have a humidifier running too. My shrubs didn't cost more than a basic bouquet of flowers from the local grocer so I'm tempted to experiment just to see what would actually happen. I've tried to read as much as possible about protecting plants in containers in cold climates and there doesn't seem to be much empirically-based information out there.

It would be great to see some photos of yours and anyone else's balcony that has the time to do that. It's not easy to get examples of what real people do with smaller balconies as opposed to larger terraces.

Seacat

Seacat, let's hope we don't experience many -27º C....for those still using fahrenheit....minues 27 is about 18º below zero.
That's awfully cold no matter where you think it is.

Seacat, I haven't seen those kinds of temperatures for quite a while. Perhaps up on the balcony and with winds being what they are at that height, that might explain why you are experiencing such low temps.

On balconies the big enemy is wind. Wind --especially in winter--is very drying. It can dry out a plant that has not been given sufficient moisture to its roots in no time.

The cardboard box may be a good idea. That and placing your plants so that wind is not a factor.
Sunligth, as suggested, it can indeed play havoc with how the plant might dry out quicker. Wind, and sun...wonderful ways to feed our plants but must be given in spurts so that we don't overfeed them.

I believe in the bubble wrap...or styrofoam placed on the insides of the containers before the soil goes in.
Then another way to deflect the hot sun....and wind...is to wrap the outside of the container with aluminum foil...especially on the sides where the sun is likely to bear down in the afternoon.

Water is important. The plant must be given sufficient water to fend off drying. But, the container should be lifted...an inch or so is fine, so that water, when given, drains well and doesn't freeze under and on the container.
Air can pass under and around the container.

Chairs, so stored on a balcony can be used to ward off wind with the added benefit of burlap. Tables, turned over --if they can stand up to being hit with wind, can come in handy.

I wouldn't suggest you take the Alberta Spruce indoors without at least giving it some warning. Such abrupt change of temperature can only cause it to speed up drying.
Alberta Spruce it does appear do not need any further help in that regard....they are not the best for retaining their moisture. You might try to acclimatize it though...in for a short stay, back out...back in longer.
I think though that particular evergreen is best suited outside in the garden or at least where it can get ultimate protection.

My boxwoods stay green on my porch during the winter as well as my sprude3s , but mose of my perineials I cut back in january and let them come back in the spring.