I've been growing a vine maple in the ground for about four years. The plan is to get a reasonable sized trunk before trying to do any real styling. I just prune it with garden shears three times a year or so. Just to keep it in some sort up shape. Every other year I have dug it up and root pruned it. The idea is that when I move it to a training pot there will already be some ramification of the roots. I think it will be ready for the training pot next year, perhaps. The trunk caliper is 1.25 to 1.5 inch, now.

Sam

samth, you could probably attain more growth if you'd stop cutting it back 3 times a year. You could have 3-4 inches in 4 years time if vine maples grow at all like the maples I'm familiar with. (They're not native here, red, silvers are what I'm judging against.)