I love dogwood (cornus florida) and would love to see one as bonsai, but every time I've read about someone attempting one their ends up dying.
Rocky Mountain Bonsai had good one but it apparently died in 2019 for unknown reasons. As a fellow beginner, I would recommend you wait some years and get some experience on taking care of bonsai and transplanting before attempting to lift a dogwood. You can always come back and dig it up down the line, it'll only get a better trunk.
You have a good eye in that this dogwood has awesome roots and a good base. If you were to collect it, I personally would chop it around here. Normally you would chop lower, but I actually like the natural taper on this tree already.
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