Is your reason for doing so a very high water table or poor drainage? Are you going to build a berm up around the sides of the plant so that soil surrounds the pot?

1) Because of high water table.
2) No, I don't plan to cover the side of the container initially. I will let the bottomless container sit on the soil until roots get established. After a few months, I will eventually cut up the container and put soil on the side to cover exposed roots. Not smart?

Is the tree appropriate for saturated soils?

Why not just plant the tree now in a small raised bed? What you propose will work, but there are several physiological reasons that guarantee slower growth & establishment - at least initially.

Al

Thanks for the reply.

1) The plant does not like saturated soil but will not die. It can stand occasional standing water.

2) Except for timed automatic irrigation, once planted, the tree will be practically abandoned. By leaving the side unexposed, I hope the tree has a better change to survive irrigation malfunction and zero human intervention for a month or two.

I am planting an Arborvitae from HD in the NW Hills of Connecticut. As I want it grown yesterday and there are tree roots to trees I don't want to harm, I was only able to dig a small hole; so, I filled the small hole with top soil & peat & tapped it down. I placed the Arborvitae on top of that hole and using wood to hold it in place, piled more of the top soil & peat mix around the 3 gal root system making it into a 3' x 3' x 1-1/2' box. To me this is a small berm. Do you think the tree will be happy with it's new home? Do the roots generally grow down, or do I need to make the soil box wider? I don't want to add too much soild so I don't suffocate the existing trees/shrubs roots. I also read in one of the forum about rinsing the Arborvitae's roots free of the junk soil that it was shipped with?? Thank you for helping this newbie.

My tree experience tells me they suffer in confining containers. They suffer more when the sides of the container collect heat and transfer it to the container soil. The soil mix used for containers is required to be fast draining to allow the needed oxygen to be drawn into the root zone as the irrigation water exits. Hot roots is not a good thing. If you are going to plant your tree in a berm for the sake of drainage, I would do it now. Generally I would hesitate before planting a new tree on top of established roots of another tree which will have the ability to suck up all the moisture and nutrients the new tree will need to establish. Al