Japanese maple

[gnichols]

Rather than sitting back and not engaging with this community I'll join in. Best way to learn something. I've had this shindeshojo for at least a decade and clearly, given it's age have no idea what I'm doing. Although at times over the years I've just enjoyed the spring foliage.
I'm not entirely happy with the lack of movement in the main trunk so considering chopping to the first side branch where the small new growth could turn into a new leader? However I'd really like to aerial layer the top instead of chopping and discarding. This pic was from August. I'll post a current one when I get a chance.

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[TimS]

I'll give my opinion but feel free to follow what others say over me as i've only be seriously applying myself to Bonsai for about 3-4 years so there will be many people with vastly more experience than me on here.

Shin-deshojo is a beautiful cultivar for bonsai, especially with the spring colour as you say

A more recent photo would be good but i don't think you need to cut it down to one of the lower branches for two reasons.
1. They could be used as established primary and secondary branches if you are happy to grow the tree around that height or a little taller
2. Given their thickness and they way they emerge (basically right angles) they will not be able to be bent to any degree using wire.

If you were to use on of the lower branches as a new trunk line (because they will not bend at that thickness) it would mean changing the planting angle to lean the trunk in such a way that the branch then creates are more 'flowing' line with the trunk toward an apex. Honestly i don't see an angle where this would work from the point of view of creating an aesthetically attractive trunkline.

Japanese Maple will bud on bare wood, even very old wood on the trunk when they are in good health. Simply by bringing it to a good state of health you will find that new buds may emerge on the trunk and on those branches that offer you options to grow more primary branches off the trunk and create ramification into secondary branches from new buds that appear on those three primary branches. Especially up the top you will find you get a profusion of buds that will help to both disguise how thick the trunk is toward the top and build a more tapered apex.

You can definitely air layer Shin-deshojo successfully, i have done so on mine though a thinner branch, it took almost exactly 5 weeks from late spring into summer for roots to start emerging and i was able to separate the layer toward the end of summer. It will likely take longer before you can separate it with a larger diameter trunk needing to move more water and nutrients though.

As i say, this is just how i would approach it for a long term result.

[KIRKY]

If you decide to go with Tims idea. I would still shorten it just a bit, the top right branch is too thick to be up that high on the tree. Looking at it, it is thicker than the two lower branches. Also the knuckle left hand turn at the very top has to go.
That will never look good.
To airlayer it you would still need to remove the two areas above. In light of that not much left to air layer
One question, is it grafted? Difficult to tell on the pic.
If grafted I would air layer above the graft, then plant at a new angle and shorten to the first right hand branch as new leader. By doing that it would give you taper and a new direction. If it were mine and grafted that s what I would do.
Cheers
Kirky

[gnichols]

No it doesn't appear to be grafted. I took another pic today but doesn't show anything other than a reasonably healthy tree. Might just let it grow out for a few years.

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[shibui]

Given that it is a named variety and there is also a distinct change of bark on the trunk I would say it is likely that this is grafted.
Kirky's advice about layering - is it really worth spending most of the year getting another second rate tree - is spot on. Far better to start another one or pay a bit for a good trunk. By all means layer good material but just chop less valuable trunks and get on with the job of making good trees.
Japanese maple is always a favourite to start with but in reality they are a demanding species. Growers really need to understand pruning and pinching to maintain good shape and prevent lumps and reverse taper.
Only one view of the trunk for this tree so it is difficult to give sound advice but from what I can see - lack of taper, coarse branches (especially 2nd branch) reverse taper are the difficulties. Trunk chop at first branch is always an option but how long would the regrow take? Chop would give better taper but, as Tim points out, can you bend that branch to make good trunk flow? Current right angle would be too awkward The tiny secondary shoot there may be an option but would set development back even further.

[gnichols]

Noted. The more I fumble around with JM the more I'm realising I should probably practise on other species.

What's the saying, the more I learn the less I know.