Winter window boxes?

Winter window boxes?

Hi all. It's officially autumn here; the leaves are yellow and falling fast and the air is crisp. I live near Edmonton, Alberta, Canada, and though fall in Alberta is gorgeous, it's much too short. So I have a question. I have window boxes outside my second floor bedroom window that are currently filled with geraniums. I love my window boxes, and having them outside my window this summer has brought me great happiness. I was theorizing about the possibility of planting something in them for winter. I'm not sure what my zone is called, so you need to know that it can get to -40*C (-40*F) a few times in the winter. I would say the average temperature for the winter here is -20*C (-4*F). I think I would obviously have to plant some kind of evergreen or else it would die. Does anyone here have any suggestions for what I might plant? I have heard that boxwood stays green during the winter, but I think this might be true for warmer climates rather than my own. It's rather boring for gardeners here in Alberta during the winter, and I'd really like something beautiful to gaze on out my window during our 6 months of cold. (By the way, I am aware of the practice of putting evergreen cuttings in window boxes and treating them somewhat like a wreath by adding things like pinecones etc. I am looking for something that I can plant, not just decorate with greenery)
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