A bonsai is not a mystery– it is a challenge….to turn a tree into a bonsai, you must heavily prune its branches and roots, and pot it in a container that fits the overall design. The size of the bonsai is maintained by seasonal trimming of new growth and periodic root pruning and repotting. Most bonsai must live outdoors in the same elements as their gigantic siblings. In temperate zones, tropicals and sub-tropicals are adaptable to indoor conditions. During the growing season almost all trees should be kept outdoors.