A friend of mine planted about 13 Japanese Maples 4 years ago. He put a 12 inch tile underneath each to start the training of the roots for the bonsai pot (we'll soon find out if this has worked or not). The tree's are about 3 feet tall and have about a 3-3 1/2 trunk. He is getting ready to move and no longer keeps bonsai's so he has given me all of these trees. My question is what exactly do I need to do to make these into bonsai trees? My plan is to put them into pots for atleast a year and cut them back. That being said, how far can I cut them back? My overall goal is to have something that looks like this

{{gwi:21482}}

I understand that this is a few years down the road but any information or tips you guys/gals can give me on how to get it started from fresh out of the ground are greatly appreciated. Also if anyone would like one of these trees just let me know. I'm going to be digging them up in the spring. TIA

-Matty