Grafting and pruning of bonsai roots
The very thought of this task, newcomers fill with horror. However, it is not a cruel thing to do at all - it makes a good thing for a plant, mimicking what would have otherwise happened in the wild. When planting a tree in a container, this process is obstructed. With occasional replanting and pruning the roots, you will do a favor to your bonsai, and it will reward you with health and a strong growth.