Bonsai Tree Repotting and Root Pruning: It is necessary to repot bonsai trees to ensure that they remain healthy and continue to grow well. Well developed fibrous roots are essential for balanced, even growth and these are produced by root pruning.
How to make a Sub-Irrigated Planter. I'm not sure I would use a two liter plastic bottle though. Over time I would fear the plastic breaking down enough to poison the plant. Perhaps a wine bottle instead.