Bonsai can be transplanted when the roots in the container have become root-bound. A root-bound condition is one in which the roots have extended themselves to the point where they are no longer able to gain sustenance from the soil. This becomes apparent when the roots are seen growing out the sides of the container. For most bonsai, this occurs approximately every three to five years. Most bonsai can live in this root-bound condition, providing they get ample water. However, this is an unhealthy situation and should be avoided.
Root pruning is not a hazardous operation if it is done at the right time of the year and if one is careful not to take away much of the soil from the soil-root-ball. One can safely take away one-third of the total volume of soil from the tree providing it is done just before the growth starts in the spring.
To repot, turn the tree upside-down and tap until the pot can be lifted up and away from plant. If any roots are wound around the bottom, unwind and snip them off without disturbing the remainder. (If repotting to a larger pot, length of new pot should measure 1/2 to 2/3 of the plant's foliage spread.) Cover pot's drainage holes with screen, then place fresh soil min, 1/2 inch or so deep into the pot for new roots to grow into. Place the plant upright onto the soil. Fill in any spaces around the sides with additional soil. Press plant down and firm soil around the sides.
To give the appearance of age, the upper one-third of the root structure of a mature bonsai is often exposed. This is especially effective if the roots have good girth and form. Twisted and tangled roots should be straightened before potting or repotting a tree to achieve an aged appearance.
Bonsai can be classified into five basic styles: FORMAL UPRIGHT, INFORMAL UPRIGHT, SLANTING, CASCADE, and SEMICASCADE. These classifications are based on the overall shape of the tree, and how much the trunk slants away from an imaginary vertical axis.
The numerous Japanese bonsai styles are principally variations of these five basic styles. The basic styles apply to trees with single trunks. The single trunk style is a basic design that is simplest to shape because the one trunk determines the overall composition.
Before deciding on the shape of your bonsai, study the tree carefully, and take into account the natural form of the species. Observe the way nature trees of the same kind grow in their natural setting to achieve an impression of age and reality.
Decide on the final shape and size of your bonsai before starting. Make a rough sketch of what you wish to create and use it as a guide. Strive for flowing form when shaping bonsai. Visualize the overall theme and try to get a three dimensional effect. Remember to select the front, back, and sides of your bonsai before pruning, and don't forget to create a pleasing form for your overall design.
To keep your bonsai tree small, compact, and shapely, pinch or snip off any new shoots that are aimed in the direction you don't want them to grow. Generally, it's best to pinch off those that are aimed upward, downward, or toward the trunk or interior of the tree. Since new buds or shoots are very soft and juicy, they can be pinched off easily with the fingertips. Pinching allows you to easily control the shape of the tree, and is one of the most enjoyable and rewarding aspects of owning a bonsai. Neglecting to pinch will eventually result in the tree needing to be reshaped by wiring and pruning growth that has become hard and woody. You need spend only a few minutes several times a year during spring and early fall to control your tree's growth.