"Paulo" wrote in message
. ..
Sounds good tome. I had some clematies growing nicely in balcony pot. But
this last winter killed them. I have never used any protection at all, and
i
am thinking i can give better chance of survival with some kind of
protection.

I guess the isulation used for heaters should be good....

Actually, the insulation isn't to keep in the heat during the winter. It is
to keep it out during the spring. Obviously you are only going to use
winter hardy plants. So they have no problem surviving when the ground is
frozen. What kills them is the freeze-thaw cycle in the spring. When you
get early spring warmth, the soil in a pot thaws much faster than the soil
in the ground. This results in the plants breaking winter dormancy too
early. When the weather gets cold again they have no natural protection.
That's what kills them. So the idea of the insulation is to keep the soil
in the pots frozen until it is safe for the plants to break dormancy. The
other factors I mentioned -- shade, wind protection and snow burden all
serve the same purpose. That's the theory anyway.

Jim