I have a pair of 3yo red maple seedlings that I'm going to be root pruning for the first time this year. I've watched over the past two years carefully, and now it is time.

My question is, since they're not yet in leaf (nor is the parent tree), is now the best time to do the root pruning, or would it be better to wait until they've leafed out a bit?

Also, at a height of 1', they've not yet branched at all. I've never worked with red maple as bonsai before (these two volunteered in an empty bonsai pot that I had on the porch- so I decided to see if I can work with them). How can one tell on this tree where to cut to encourage branching? Looking at it, I haven't been able to see any obvious spot for latent buds to be hiding under the bark, and with three years already invested, I don't want to damage them beyond repair.

Thank you in advance.

Mattie, Iowa zone 4b/5a