I would say put them in the ground. I have 3 and am trying to grow them as a screen as they are evergreen hedge plants. You can train them as a standard - works really well.

Yes plant them in the ground. They make a nice hedge if you decide to have more than two. This plant is very susceptible to leaf spot which is a fungal disease. If the leaves drop then collect them up . In spring give the plant a spray with a fungicidal spray. In some severe cases the leaf spot spreads and kills off the plant but in most cases new leaves will grow next spring with attractive red tips and the plant survives despite the leaf spot. Next year when the new red leaves eventually turn green give it a light trim and that stimulates new red growth.