Question
Is it possible to for a green giant to grow in a decorative pot (if so, how large of
a pot).  I would like to plants some green giants in my back yard, but I also want
to take them with me if I decide that I want to sell my house.  I want to be able
to provide an instant privacy screen now and don't want to wait 3 or 4 years to
get it.

Answer
Not really possible for the long run. These will grow at maturity about 30 feet tall and 15-20 feet wide growing alone. The root system will need to be at least 15 feet wide so the "pot" as you can see will need to be very large. Not the one that can be moved. I would plant them in the ground and IF you move get new ones for that location.