how do I turn young trees in to bonsai trees? I have about 20 maple trees all about 3 weeks old and want to grow them into bonsai trees.

I feel I have to chime in here to say that if you want to try growing tree material from seed, go for it! I find it very rewarding, and several of my bonsai were started this way. It does take time, but the the development of a thicker trunk can be expedited by growing in the ground for several years. One of the advantages of growing from seed is that it can be easier to develop a good nebari. I've found that nursery stock I purchased often has problematic root structures. With seed, there is more control over the plant right from the start.

If you decide to plant seeds, then you might also want to obtain some trees from other sources so that you can hone your skills while the seedlings are growing. I find it nice to have a range of plant material with which to work.

I have a couple of pear and apple trees that I plan to dig up next year and transplant to grow boxes. They were grown from seed I planted 6 years ago. They'll probably spend the next 4 - 5 years in a grow box, before they are planted in bonsai pots. I think 10 years is probably not unreasonable for the progression from seed to bonsai pot. Maybe my trees will never be featured on the cover of a magazine, but they still bring me hours of enjoyment, and I think this is what counts. If I were only interested in the end result, I'd probably just go out a buy a bonsai...but would take all the fun out of it for me!

I'll post photos of the pear and apple trees next spring!