The answers to what you're asking are huge, not something like "You just do this, that and the other thing and end up with a bonsai". It's not only a long process, but a long learning curve. While you know and grow trees now, which will put you ahead of the game, growing trees in little pots is different. Growing them in the ground first (as you're doing) is the fastest way to develop the thick trunks that are so important, and the general rule is to chop them back at some point (3-5, or more years) above the lowest branches (except in trees you can be sure of budding back below that) and training new smaller branches up to be new leaders, and adding taper in the process. Chopping can be done once or a few times over many years. What also matters is learning to prune branches for ramification (short internodes and more foliage), and directional growth, as well as pruning and encouraging roots to grow laterally rather than deep, and ideally as evenly spread around the trunks as possibly, though that works best when trained into the trees from the youngest age. You not only need to know growth habits of various trees, but learn about soil mixes used in pots (very different from inground) to facilitate fast drainage, but also how to use what wire to shape trees, and very important - how to water them properly in the pots, very different from house plants and from inground or large containers, as well as about what styles suit which trees, as not all trees make good bonsai for various reasons. I suggest you try to find a local club nearby, as they're great places to learn, plus read whatever you can (apart from books) at www.evergreengardenworks.com - great basic info., and www.bonsai4me.com - an overview (though many trees addressed may be tropicals suited to indoor growing), and hang out at www.bonsaitalk.com - the best all-round forum there is, as well as www.bonsaisite.com and www.bonsaichat.com. It doesn't always take 'years' to produce good starter bonsai - the point is to give the illusion of age and interest, but always keeping in mind that bonsai should look like trees, not some contorted and peculiar decorations, though there's a lot of $)#U% out there, both in mass produced trees (3 yr old cuttings!) from China being sold like hotdogs, with bad information tags on them (we call them mall-sai), and tacky 'S' shapes.

Thank you Lucy, I thought that was great information. You seem to have a lot of knowledge on Bonsai.
I know the bonsai is a big subject with so much to learn. You say that I'm a little ahead of the game by already having trees in the ground. Would you leave the trees in the ground for three to five years to do the chopping and ramifications or does in need to be in a bonsai training pot by that time? Do i need to put a few one year old seedlings in training pots too? I would think you could leave a three or so years, (trident maple for instant) in a three gallon pot then do some chopping and training before you put it in a training pot?? I was thinking ,, if i cut out some 3/4'' plywood , plant it in the ground , say about six to eight inches then a seedling on top of it , that should train the roots to go out. Whatcha think ? Of course it would be staked and strapped down so the wind wouldn't blow it over..... I don't know ,just thinking out loud.. Thank you again Lucy !!

Lots of people plant their trees over tiles (or anything flat that won't rot away in a year), so that's a good idea. The length of time you leave them out is entirely up to you (how fat do you want the trunk?), though maples can take longer to fatten up, so you choose how important fatness is for a particular tree or style (there are some that it isn't crucial for, like 'literati'). What you can also use the plywood for is a slatted ('training') box, with screening between slats on the sides, and it's essentially used to 'grow out' trees, sort of a compromise between in-ground and containers. It's best to not root prune before setting out as it'll slow growth, as will pruning the tops, but you can still wire and prune foliage for neatness to some extent while you're waiting for them to be pot-worthy. Be conservative about staking (you're probably smarter about that than I am) to be sure the seedlings do gain some trunk strength and if the roots are established enough, allow them to bend to one side or the other to achieve a windswept look (but you'll have to judge safety of course).

Thanks again Lucy, Great advice.. lol... I could sit down you for a few hours and learn something ... Take care !