If you are a devoted bonsai enthusiast and you have already mastered the proper skills to properly water, wire, train, and style your Japanese maple bonsai, but you still cannot get the miniaturized tree trunk to grow thick enough in proportion to the tree branches, then it is time to change your training approach to your bonsai tree.
The best time to start creating a large trunk for your bonsai Japanese maple is during winter. Ideally, it is best when the miniaturized tree is around thirty centimeters in height and it is at the point when the buds are about to burst. Now, before you think of creating a strikingly thick trunk for your Japanese maple tree, you must first develop a good and an evenly distributed root system for your bonsai maple.
To do this, you must find an old bucket or a very large open-mouthed container to use as a planter for your tree. You can even plant directly into the soil. Find a location in your garden or in your yard which has good compost and has a soil type which easily drains. These two factors will promote the growth of the root system so that you will end up with a Japanese maple tree with a large trunk.
During the first twelve to fourteen weeks, you must water the plant well. Place fertilizer (either the organic or commercial kind) on it. Take note that when you fertilize, make sure that no fertilizer particles end up over the root system of the Japanese maple tree. You need to make the tree roots search for the soil nutrients on their own so that they will be forced to expand.
Once the root system has developed, choose which part of the bonsai maple tree that you want to serve as the front area. Remove the top buds, then prune down sideways the two healthy buds that grow together. Your Japanese maple tree is spurting fast at this point, and there will be an obvious enlargement on the trunk of the tree. The two leads where you have previously cut the side buds of your tree have grown bigger as well. This will happen six months after you have begun enlarging the tree trunk of the bonsai. Once you are satisfied with the thickness of the trunk, you can finally decide the style and overall shape for your Japanese maple. Sever the lead branch using a small handsaw. Cut cleanly so that you will not damage the bark. Finally, transplant the bonsai Japanese maple into a shallow pot.