I have three of these and I think it will not be a good idea to leave them like that over winter. This is in Toronto Canada. Here is the hardiness map. I was thinking that storing them in a shed my work. How much light do they need?
Update: one year later
Not a bad winter all in all. at some point the planters where full of ice, the plants were covered in ice because the water did not drain (the bottom holes plugged) and it froze filling the planters up