The size of the initial pot should be considered a judgment call. Your root-pruning efforts last fall should have paid off in the form of more fine roots close to the tree, but how many fine roots there are sort of dictated how much you can prune off the roots to fut it into a pot - especially since you indicate the plant was stressed going into dormancy. It didn't GAIN any energy over winter, so it will be weak now, and needing it's carb reserves. The soil should be free draining and well aerated. I'm going to suggest you read the link below, which addresses container media. The recipe called 'the gritty mix' at the end incorporates almost all (if not all) the desirable characteristics of a bonsai soil, and it's adjustable for water retention. If you have more specific questions, you can ask there or here. Repot at the first sign of bud movement. After that, you'll need to protect the tree from freezing temps, so moving it in and out of the garage or shed after it leafs out, until temps are reliably above freezing, is the best plan. The larger the container and the more air the soil holds - the better, but if you choose a heavy, water-retentive soil like MG or others based on peat, container size is much more critical. After you make your soil choice, I can help you with tips on how to get the most out of whatever you're using - and I can help with a fertilizer supplementation regimen. The basic soil I use for all my trees Al Here is a link that might be useful: About container soils in general - a concept

And it is far less stressful on the trees if you intend moving them to transport in containers rather than digging up and disturbing the root system. I grow a lot of JM's in containers. I agree that locating and using a high quality potting soil is more of a limiting factor than pot size. A 20" container should get you through the next couple of growing seasons without much trouble....no need to step up the pot size gradually. Visit the Container Gardening forum for some direction on creating the ideal growing medium (check out posts referring to a "gritty mix"). And be aware that containerized growth of trees - any woodies, really - requires some ongoing attention with regards to fertilizing, watering, winter protection (if necessary) and the possiblility of root pruning should the trees not get planted inground in a timely fashion.

First, I doubt you have a Bloodgood - the leaves are far too small/lobes too narrow, even on a young tree, for that cultivar. There are a lot JM's being sold as Bloodgood that are just seedling trees. That could account for the leaf aberration as well as the coloring. Bloogood is a very deep wine red color, although it can bronze up or lose some of its redness in full sun in hotter climates. But it should never have distinctly green leaves like what is showing in your photo. And no, it will not produce any more new leaves now. It is fall and the tree will be entering dormancy soon and dropping what remaining leaves it has. I hope you didn't pay much for it :-) It is in bad shape, suffered some serious drought stress and looks like it has some tip dieback as a result.....not to mention a good likelihood of labeling issues. Just get it planted and hope for the best in spring. btw, if you have more questions, it is advisable to start your own thread rather than tacking on to an old, stale one. And there is forum dedicated specifically to maples as well that will give you very precise JM advice.

If this is to be the permanent home for the Osakazuki, I might reconsider that siting. Osakazuki gets to be a big JM - one of the largest growing cultvars - and is really more of a specimen tree than something that could well be overshadowed by a much larger growing nearby red maple. I'd be inclined to give it a space all of its own so it can really shine. Maybe somewhere with a more evergreen backdrop so the gorgeous fall coloring Osakazuki produces will be really be highlighted.