WOW what a GREAT idea! now I am not a very experienced grafter to say the least but, in theory it sounds good, because you are essentially doing the same thing when you make a new tree via a graft. As long as you do it before the plant buds (in between winter and spring, give it a couple weeks+ to recover) you should be fine. I have seen trees that people are making now a days that have two different types of JM growing from one stem, but never seen a large or even medium tree of that. Because one stem will most likely take over more than the other based on growing speeds, etc..But I would love to hear some more peoples thoughts on this one because I might do the same if it works! I had a beautiful lace leaf tree had one of the two main branches broke because of a ladder and it would be awesome to add another branch where the original one was. Good luck!

Sketch,

I believe the way the grafting was done is to take two branches still attached, having them meet and force the graft to occur by cutting out some of the bark/wood and strapping them together until the graft held. In my research I ran across maple bonsai where they grafted other, rooted (same type) maples or roots to the bonsai for shape by doing something called approach grafting. Once the graft took, they severed it from its original tree. From what I saw, approach grafting might be the best bet to fix your tree, or if you have a branch you can "introduce" to the other side while still leaving it attached until it takes is probably your other option... but I'm no expert in this.

Nice to see you removed the stubs. They are the first sign of an amateur.
Do you feel you need to get the additional bracing for snow and ice loads? Why not prune with that in mind to avoid the unnatural branching pattern that a bridge graft would give?

I prune starting at the bottom and work up and out, taking out any branch that will be superceded by the branches above. Then I thin a lot of side growth on the branches that are left, taking out the lower ones. What's left doesn't have enough wood to catch a lot of snow and ice. I have to be careful of not showing a lot of trunk to the southern sun as it will scorch the trunk. I can show more 'leg' as the canopy spreads. The result is a lot more interesting form than the mounded mushroom, Dutch cut look, you generally see.
Mike
{{gwi:1037888}}
Morning picture in the Fall looking south.

Mike

Love your maples... I would like to avoid the "mushroom" cut look you mention, however, with the older tree it would involve the extensive removal of some very large branches (they weave back and forth in the canopy...apparently those previously taking care of it didn't know about the "cut out branches growing inward and/or crossing") to open the tree up, and I don't know if I can achieve a balance between not too much removal too quickly and how vigorously it grows and still get there. Still have some stubs I haven't dealt with and I've left a rather awkward looking, low branch that's south facing to provide some trunk some protection.

With the little one, it's a more obvious route, but I have heard and seen of maples splitting in the middle when pruned like this due to snow. Am in Toronto, so heavy (as in wet) can be an issue.