Answer: Arborvitaes as a group are quite slow growing; I would not expect this one to grow more than a foot or so per year when planted in the ground. However, based on my experience I would not recommend trying to grow this plant in a container under home conditions. This is very stressful on woody plants; in a nursery situation they are carefully watered and fertilized and monitored on an ongoing basis, there is a special potting mix and a scheduled routine for their care.
Even if you managed to keep them going over the first summer, you would risk losing them in winter. The container does not insulate the roots the way being planted in the ground would insulate them, so they are exposed not only to extreme cold but also to oscillating soil temperatures and freezing and thawing. Both of these are very stressful on plants and as a result, even if they do manage to survive they often succumb to a pest or disease the following summer.
I'm sorry I can't be more encouraging.
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