Not too sure about the age, probably 8-10 years.
To get good taper, best way is still the good old method of chopping the trunk and growing new leader to the size you want, then chop again. It takes time but you get the taper you want. Below is a Japanea maple shohin being grown this way. The leader is thick enough and I will chop it off soon and use the bottom small branch as a new leader. Once that branch is thick enough, I would have the final height, the rest is building branches etc.
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I also do the chop and grow for larger tree. This is a Chinese elm I got from a landscape nursery. It has a nice root flare and a gradual bend in the main trunk. It was at least 12 ft. tall when I got it. Chopped it down around May this year, let it budded out and selected a new growth as leader which has thickened quite a bit. I put a chopstick next to It and a 4" pot near the base for size comparisons. It will take may be another 4-5 years to reach the desired thickness before working on the branches. There is no shortcuts for growing good taper, one can accelerate it by directing all the energies to thicken the leader faster. The envisaged final height would be about 24-26". Look forward to seeing it as a resonably good looking tree in about 10 years.
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