Unless you bury the pot (the rootball) for winter, or bring it inside a building or garage, unheated, and allow it a dormancy without the frigid winds of winter hitting the rootball, even potted... it will die.

Plants' roots require insulation against the brutal winds of winter in zone 5... even 5b. It's not the snow or general cold that kills plants... it's the frigid winds hitting them when they have no or little insulation. Most plants that survive in northern zones drop their sap into the roots for winter, or die back to the ground, you'll notice. That rootball cannot survive without thick insulation, like the ground provides, and snow or a good mulch layer provides.

The plant would probably make a fine hanging basket... but it will require protection of the rootball in winter.

I understand what you're saying and I'm concerned about whether or not it's viable, too. This is why I'm targeting a tough plant that is hardy to zone 3. It's sort of an experiment. My understanding is that the rootball should be able to survive the ambient temperature (if I stabilize it against freeze-thaw cycling), but that what I really have to worry about is water management as the winds will tend to essentially freeze-dry it.

80% of our winds during the winter come from northwest by west, and I'm putting it on a corner balcony that is blocked by a brick wall on both the north and west. My hope was that using a fairly large pot with a good volume of soil, wrapping it, mulching, and, hopefully, further shielding from the wind by its own trailing branches would give it a fighting chance. This might be too optimistic.

Either way, even if I have to stow it somewhere to overwinter, I'm still interested in the right pot for it. I did just find the Plastec Adjustable Plant Hangers, which might do the job with some other conventional air-pruning pot.

This post was edited by Mister_A on Sun, Jul 27, 14 at 18:08

Well, I wish you the best of luck... but I know that if it were me, I'd take it down at the appropriate time and store it in an unheated, closed shed or garage for winter... and when it snows, I'd take a small shovel of snow and drop a little on the soil surface to emulate the moisture it would get... and allow nature to let it melt in slowly or sit there...

I don't think I'd trust in a mild winter, or that frigid winds couldn't or wouldn't whip around where we don't expect them to... especially as the plant is hanging, and has no contact with the ground.

It could possibly survive... but I would not place a bet on it.