The 'Bonzi" method (Bonsai) requires that the roots be trimmed every few years - are you really prepared to repot ten trees of that size on that basis? While they will grow more slowly as time goes on, they will continue to grow - top to bottom. Plus, of course, you'll also have to work on the tops and trunks will thicken. How large are the containers you had in mind?

I don't know this for sure, but it seems like it would be a lot easier to just stick these trees in the ground. With the size you're talking, it doesn't sound too much shorter than a regular cherry or apple, and you can also get dwarf trees. From what you are saying, it is sounding (to me) like each tree would be about 10-20 feet wide, which would practically require a forklift to move. I think it would cause you much less trouble to put these trees directly in the ground.
-Jmcat

When you say "concrete raised bed container", I'm trying to figure out exactly what you are planting in.

When I think "raised bed", I think of a bordered, raised area placed directly on the ground. In that case, you would basically be ground-growing.

When I think "container", I envision that there is a bottom, and no direct contact with native soil (except perhaps via a drainage hole).

Managing your trees will vary somewhat on whether or not you truly have container or a raised bed. Also, the dimensions of the root growing space will also dictate how you manage it.

Many of us have probably seen very large trees growing in very large containers. With these large containers, of course no root pruning is carried out. Large mechanized equipment is required to move them. Their growing conditions are fairly close to actual ground-growing.

As the size of the container gets smaller, the need to manage (prune) roots, and change soil becomes more important.

Having said all that, I am currently growing a plum tree in a container that I intend to keep at about 8' to 10' (it is 8' now). It is in a round metal container (like a half of a 55 gal. drum).

I am using bonsai techniques to improve the appearance of the tree. I am currently training a small side-branch to eventually become an upper portion of the main trunk. I have kept all foliage above that branch as "sacrifices" to help thicken the trunk below. When the time comes, I will be "chopping" all of the trunk above my chosen branch, then this branch will be come the new trunk above this chop. By doing this, I will be adding some "trunk taper" and some "movement" to improve the overall appearance of the tree. Over time, I will select another branch higher up, and repeat the process for some more taper and movement. It will take years.

Every few years I will root prune the tree, and change the soil. This will not be easy. I did just that with an 8' Liquidambar that I am growing in an identical container. Last winter, I carefully placed the container on its side, and "rolled" the root ball out of container, being very careful not to damage any important branches. Once out of the pot, I root pruned, and replaced the tree into the container with some new soil.

This is not an easy job with a tree this large. It might even be more difficult to remove the root ball from a concrete container like you propose. I look at it as a challenge, though.

If your container is too small to allow unrestricted root growth (like true ground growing), then root pruning will be required to keep the tree healthy and vigorous. If the containers are too heavy or unwieldy to allow the root ball to be removed, then you will need to adopt an alternate strategy for root pruning.

This strategy could consist of periodic cutting and removal of the roots and soil from the perimeter of the container, and replacing it with new soil. You could also consider taking pie-shaped pieces from the root ball, allowing you to prune closer to the trunk. You would take these pie-shaped pieces in a rotating manner so that every few years there is a complete removal and turnover of a large portion of the roots and soil from around the trunk. In this scenerio, you will be unable to prune the bottom of the root ball. The downside to this method is that you will be unable to identify and correct circling roots, and the like.

Large trees can successfully be maintained in small containers, but you have to work at it. Only you can decide if you are willing to go through all the effort.

There's some good advice over at the CONTAINER GARDENING forum that will help you immensely. I suggest browsing over there for a while.

Good luck!

I'm a little confused, why would you want to do this? Normal modern fruit trees, and certainly apples, trained as espalier are unlikely to be taller than 8'. So seek out suitable varieties to do this, most likely on dwarf rootstock, and plant them in the ground. If you are specifically looking to have container grown plants, there are many modern varieties which have been developed precisely for this purpose, although they will stay columnar rather than espalier. Lin that might be useful.

Here is a link that might be useful: Plant an espalier apple tree