Question
Can I plant aborvatae in one half wine barrel containers?  Will the
root ball soon outgrow the container?  Same question for low
growing juniper for ground cover?  Thanks much. Darrel

Answer
Darrel,
I have seen many Arboriate planted in these kinds of containers. It is fine as long as you realize that you will reduce the plants life span greatly (possibly cutting it in half or 10-15 years). The Arbs will be fine for maybe the first 5 to 6 years, then you may experience some die back from root restriction. One way to mitigate some of this dieback is to control the height of the Arborvitae through shearing and selective pruning.
You will have better luck with the Junipers, as they will not require a larger space.
Thanks for the question,
Ed Gulliksen