I would put the tree in a one gallon nursery pot with good drainage. Place a board (I've also used a saucer turned upside down)about 6-8 inches down to discourage a long tap root. And fertilize often with 20-20-20. I would also use a cake fertilizer. Maples grow quickly when fertilized, so prune often to discourage long internodes.

Have fun!
Laura

Pruning it often is going to slow down the thickening of the trunk.

There's an excellent article on Brent's site about growing trunks.

http://www.evergreengardenworks.com/trunks.htm

I have tried finding out how big a one gallon pot is but finding it difficult. I work in litres but most garden centres around here (England) have cm diameter to make it even more confusing. Any one got a convertion?

Thanks

Do you have 4 liter pots? That would be about the same. Here's a conversion site...

Here is a link that might be useful: gallons to liters