When should I prune and rewire this young maple ?
I know it’s quite big and not in a nice pot yet but I’m trying to get as much growth as possible .
Like many things in bonsai, it depends. (Keep in mind, the following is from a beginner in the hobby)
If you're goal is to grown it out and have a bigger tree later on (as you stated), then don't prune it. The more solar panels it has and the less wounds it needs to heal, the quicker you will have a bigger sized tree.
"Do I really, not prune the tree at all until it is much bigger?" Well it depends. If you are having some issues with leaves crowding themselves out, then you will probably need to prune some leaves to get better sunlight and airflow. If you are having some reverse taper (or can reasonably predict where it will occur) on trunk/branch that you know you probably want to keep, then prune away.
If you're goal is to have a small tree AND you are happy with the trunk sizes, a chop is in order.
As for wiring, you really only want to start wiring at this young of an age to get some radical movement in the trunk line as the bends will soften as the trunk thickens. Any branches you are reasonably confident that will be in your final design will probably need wiring to get some bends in them before they become brittle.
As for the picture: This is a silver maple that volunteered itself 3 years ago. I have wired the primary trunks to try and get some radical and interesting bends in them. I'll need to go in later and reapply the wire. I plan to make this into a raft style much later in life. So for now, I am only managing and trying to layout the future trunks as most of the branching will probably get cut off with some trunk chops.
