Shaping and dwarfing are accomplished through a few basic but precise techniques. The small size of the tree and the dwarfing of foliage are maintained through a consistent regimen of pruning of both the leaves and the roots. Various methods must be employed, as each species of tree exhibits different budding behavior. Additionally, some pruning must be done seasonally, as most trees require a dormancy period and do not grow roots or leaves at that time; improper pruning can weaken or kill the tree.
Most species suitable for bonsai can be shaped by wiring. Copper or aluminum wire is wrapped around branches and trunks, holding the branch in place until it eventually lignifies and maintains the desired shape (at which point the wire should be removed). Some species do not lignify strongly, or are already too stiff/brittle to be shaped and are not conducive to wiring, in which case shaping must be accomplished primarily through pruning.
To simulate age and maturity in a bonsai, deadwood features called "jin" and "shari" can be used to good effect with coniferous bonsai, especially: "jin" is created by removing the bark from an entire branch to create a snag of deadwood, while "shari" involves stripping bark from areas of the trunk, simulating natural scarring by limbs being torn free. Care must be taken when employing these techniques, because these areas are prone to infection, and removal of too much bark will result in losing all growth above that area. Also bark must never be removed in a complete ring around the trunk as it contains the phloem and will cut off all nutrient flow above that ring.
Watering
Because of limited space in the confines of a bonsai pot, bonsai care can be quite difficult. The shallow containers limit the expanse of the root system and make proper watering practically an art in itself. While some species can handle periods of relative dryness, others require near-constant moisture. Watering too frequently or allowing the soil to remain soggy can promote fungal infections and "root rot". Sun, heat and wind exposure can quickly dry a bonsai tree to the point of drought, so the soil moisture should be monitored daily and water given copiously when needed. The soil should not be allowed to become "bone dry" even for brief periods. The foliage of some plants cultivated for bonsai, including the common Juniper, do not display signs of drying and damage until long after the damage is done, and may even appear green and healthy despite having an entirely dead root system.
Bonsai should not be allowed to become waterlogged, as this may lead to root rot. Neither should the soil be allowed to dry too completely before rehydration. Watering techniques vary, with some growers preferring to water with a fine rose on a watering can or hose, while others immerse their trees in a water-filled basin to the height of the container lip.
Repotting
Bonsai are generally repotted and root-pored around springtime just before they break dormancy. Bonsai are generally repotted every two years while in development, and less often as they become more mature. This prevents them from becoming pot-bound and encourages the growth of new feeder roots, allowing the tree to absorb moisture more efficiently.
Wiring
Bonsai wiring is one of the most powerful tools to control the shape of the tree. The best time to wire a tree is in spring or fall when there is not as much foliage and the tree will not be too stiff. (Trees become stiff in winter while dormant because the sap pressure of the trunk and branches is much lower.)
To wire the tree, wrap the trunk. Then wrap each branch in spirals of bonsai wire so that the branch may be bent. The tree will then train the branch to grow in the desired direction. Another method of wiring involves attaching weights to the branches, causing them to sag and creating the impression of age.
Generally, wire is left on for one growing season. The tree should not be allowed to outgrow the wire, since this could cause the bark to become bound to the wire, making removal traumatic. When the time comes to remove the wire, it should be cut away in small pieces (rather than winding it off) as this will cause less damage to the foliage.
The thickness of the wire used should be in proportion to the size of the branch larger branches will require lower gauge wire. Two pieces of thinner wire paired together can be used in lieu of heavier wire. It is bad form to let any wires cross; this is most readily accomplished by starting from the base of trunk and working up.
When bending the branches, one should listen and feel for any sign of splitting. When bending a branch near the trunk extra caution should be used, as the branch is generally most brittle near the trunk. It is possible to gradually bend a branch little by little over the course of several months.
When working with the branches, consideration should be given to the style desired.
Tools
Special tools are available for the maintenance of bonsai. The most common tool is the concave cutter, a tool designed to prune flush, without leaving a stub. Other tools include branch bending jacks, wire pliers and shears of different proportions for performing detail and rough shaping. Anodized aluminum or copper wire is used to shape branches and hold them until they take a set.
Fertilization and soil
Opinions about soil mixes and fertilization vary widely among practitioners. Some promote the use of organic fertilizers to augment an essentially inorganic soil mix, while others will use chemical fertilizers freely. Bonsai soils are constructed to optimize drainage [3]. Bonsai soil is primarily a loose, fast-draining mix of components, often a base mixture of coarse sand or gravel, fired clay pellets or expanded shale combined with an organic component such as peat or bark. In Japan, volcanic soils based on clay (akadama, or "red ball" soil, and kanuma, a type of yellow pumice) are preferred.
Containers
Every bonsai pot is equipped with drainage holes to enable the excess water to drain out. Each hole is typically covered with a plastic screen or mesh to prevent soil from escaping. Containers come in a variety of shapes and colors (glazed or unglazed). The ones with straight sides and sharp corners are generally better suited to formally presented plants, while oval or round containers might be used for plants with informal shapes. Most evergreen bonsai are placed in unglazed pots while deciduous trees are planted in glazed pots. It is important that the color of the pot compliments the tree. Bonsai pots are produced all over the world, some are higher quality than others and some are highly collectable such as ancient Chinese or Japanese pots made in highly touted regions with experienced pot makers such as Tokoname, Japan. However, highly collectable pots are not just confined to Asia, European Artists such as Byran Albright and Gordon Duffett produce unique pots which Bonsai artists collect.
Pre-Bonsai materials are often placed in "growing boxes" which are made from scraps of fence board or wood slats. These large boxes allow the roots to grow more freely and increase the vigor of the tree. The second stage after using a grow box is to plant the tree in a "training box" this is often smaller and helps to create a smaller dense root mass which can be more easily moved into a final presentation pot.
Location
Contrary to popular belief, bonsai are not suited for indoor culture, and if kept indoors will most likely die. While certain tropical plants (Ficus, Schefflera, etc.) may flourish indoors, most bonsai are developed from species of shrubs or trees that are adapted to temperate climates (conifers, maples, larch, etc) and require a period of dormancy. Most trees require several hours of direct or slightly filtered sun every day.
Overwintering
Some trees require protection from the elements in winter and the techniques used will depend on how well the tree is adapted to the climate. During overwintering, temperate species are allowed to enter dormancy but care must be taken with deciduous plants to prevent them from breaking dormancy too early. In-ground cold frames, unheated garages, porches, and the like are commonly used, or by mulching the plant in its container up to the depth of the first branch or burying them with the root system below the frost line.
Mallsai
Inexpensive bonsai trees often sold in chain stores and gift shops are derisively referred to as "mallsai" by experienced bonsai growers, and are usually weak or dead trees by the time they are sold. Often these bonsai are mass produced and are rooted in thick clay from a field in China. This clay is very detrimental to the bonsai, as it literally suffocates the roots and promotes root-rot. Very little if any shaping is done on mallsai, and often the foliage is crudely pruned with little finesse to resemble a tree. Due to the conditions under which they are transported and sold, they are often inadequately watered and are kept in poor soil, usually a clump of sphagnum moss or the aforementioned clay with a layer of gravel glued to the top, which leaves them susceptible to both drying and fungal infections. Some "mallsai" can be resuscitated with proper care and immediate repotting, although this is reportedly rare. This top layer of glued-on gravel should be immediately removed once the bonsai is purchased, and the plant should be repotted in a good bonsai soil such as akadama.
Collecting
Bonsai may be developed from material obtained at the local garden center, or from suitable materials collected from the wild or urban landscape. Some regions have plant material that is known for its suitability in form - for example the California Juniper and Sierra Juniper found in the American West, and Bald Cypress found in the swamps of Louisiana and Florida.
Collected trees are highly prized and often exhibit the characteristics of age when they are first harvested from nature. Great care must be taken when collecting, as it is very easy to damage the tree's root system (often irreparably) by digging it up. Potential material must be analyzed carefully to determine whether it can be removed safely. Trees with a shallow or partially exposed root system are ideal candidates for extraction. There is a legal aspect to removing trees, so the enthusiast should take all steps necessary to ensure permission from the owner of the land before attempting to harvest. If not, consider the right of the plant to stay where it is undisturbed.
