All potted plants will eventually outgrow their containers. While houseplants need to be "potted-up", that is, placed in larger and larger containers, the miniaturization of a bonsai trees is maintained by keeping the roots confined to the small container. On average, repotting will be necessary every 2-5 years, but the tree should be removed from its container and its root system inspected once a year. If the roots form a circular ball around the perimeter of the pot, it is time to trim the roots and repot.
When repotting remember to:
Trimming & Pruning
The main objective of trimming and pruning is to shape the bonsai into the desired form and to reduce growth above ground in order to maintain a balance with root growth.
The process of shaping begins when the tree is very young and is on-going as it continues its growth. Trimming is accomplished by using a sharp scissors or shears. This traditional tool is called butterfly shears or bonsai shears and is used for removing foliage and light branches. When heavier branches are removed, we call it pruning and the tool to use is the concave cutter, for which there is no substitute. The concave cutter allows you to remove small, medium and even large branches without leaving any visible scars. Some trees such as the Juniper should be trimmed by using the thumb and index finger to remove new growth and to prevent browning and a "sheared" appearance.
Pests & Diseases
As living trees, bonsai are susceptible to insect attacks and disease. Preventive and corrective measures include: