The gardener decides how big a bonsai tree grows. A bonsai tree can grow up to 60-80 inches (152-203 centimeters) or it can be as small as 1-3 inches (3-8 centimeters).You can decide how big your bonsai tree will get by the size of pot you use when re-planting.The general rule of thumb is:Pots depth should be equal to the diameter of the trunk just above soil level. For oval or rectangular pots, the length of the pot should be 2/3 the height of the tree. For round pots, the diameter of the pot should be 1/3 the height of the tree.