Get an Ashe magnolia instead and plant it in a large tub.

Thanks for the suggestion, bboy, think I'll get M. ashei.

However, I'm still looking for help adapting M. macrophylla to a container, cuz I already have one!

Thanks again.

I have left them in pots for several years due to laziness (or something like that) and they don't seem to be adversely affected and the roots didn't seem to be trying to get out. They seem pretty easy to transplant, so it doesn't appear that they have deep or difficult roots.

That's the only experience I have with that situation.

Magnolias, as a general rule, do not like to have their roots disturbed. That's one reason why they don't make good bonsai specimens. But I'd still be tempted to experiment, I have to admit.

Be sure to use a nursery mix, rather than a typical bagged potting medium. You'll want something with a great deal of composted conifer fines, B-B sized granite grit, perlite, etc. VERY coarse textured. When it becomes time to root prune, I wouldn't do anything but cut away (sharply) the bottom portion of the root ball. You shouldn't have to do it anymore than every two or three years, hopefully.

Thanks all for the advice. Yes, rhizo, your suggestion for root pruning is about what I was thinking, too. I may also have to take a few wedge shaped pieces from the sides occasionally also; kinda like root pruning a broadleafed evergreen. When it comes time for it, I'll let you know how it turns out.

Thanks again.

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