Answer: Unfortunately most evergreens do poorly over time in containers; they become stressed by the cold as well as by the freeze/thaw cycles of spring and fall (their roots are not as well insulated as they would be if planted in the ground), the winter sun and heat reflecting off the building and snow can cause them to break dormancy prematurely in winter and suffer cold damage or dry out, then they also become stressed by the heat and dry soil conditions in summer. Truly I would not recommend anything for this type of planting. However, if you are willing to plan on replacing them regularly -- possibly twice a year -- you could try the dwarf Alberta spruce or an arborvitae or an upright juniper. Your local professional nursery staff and/or county extension may have some other suggestions, too. I'm sorry I can't be more encouraging.
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