The practice of Bonsai began in China and Japan hundreds of years ago, and is simple the miniaturization of naturally occurring plants and trees. Bonsai trees are not "special small" trees, but rather trees that ave been slowly miniaturized from their full size.
The main areas of tree care are the following:
Watering your Tree
Bonsai Trees require more watering than most plants, as they are grown in less soil and the soil itself is free draining (meaning it doesn't retain the water and lets it pass through). The type of tree, the sunlight it is exposed to all factor in to how much watering should be done. You can tell if your Bonsai Tree needs water by looking at it, feeling the soil and if you prefer; by using a moisture meter to be certain.
Fertilizing your Tree
Bonsai plants are grown in smaller amount of soil compared with other trees and plants, therefore fertilizing and feeding your tree is key. You will want to fertilize once in the Spring and once again in the Fall to ensure maximum health and growth. Your fertilizer should contain chelated iron, nitrogen, phosphoric acid and potash. Make sure before you fertilize, to water your tree and then apply less than the recommended amount.
Misting your Tree
Bonsai trees and plants in general thrive in a humid environment, something that is somewhat uncommon in most of the world. Some gardeners would recommend misting your plants, to recreate this humid environment. The issue with misting is that it's only a short term benefit to your plant. We recommend placing a tray below your tree, which you fill with water and allow natural evaporation to do the work to create humidity. Make sure the plant is setup off the tray so the roots are not sitting in the water constantly.
Sunlight for your Tree
Bonsai trees thrive in a sunny location, and only with a few exceptions (repotting, extreme trimming) it should live permanently in a sunny spot. It's a good idea to leave your plant within a foot of a direct source of ultraviolet light. Southern (east/west okay too) exposure is best, if you plan to grow in a northern exposure location you may need the assistance of grow lights. Do not use Incandescent light as it is much too hot and does not provide a complete spectrum of light. Choose your type of tree wisely as some do better in less light and some require lots of light.
Trimming and Pruning your Tree
One of the main attractions of Bonsai ownership is the possibility to shape and mold your tree to meet your vision and desire. However there are fundamental concerns you need to keep in mind whilst pruning your tree. Balance is very important, and keeping a nice even distribution of branches over the your roots below is key to keeping your tree healthy and complete. You begin shaping your tree when it's very young, and continue to shape even as your tree ages year after year. Butterfly shears are used to remove leaves and branches as needed. Large branches should only be removed with a concave cutter. Maintaining your trees appearance while minimizing the appearance of pruning is essential.
Protecting your Tree (from disease and pests)
Similar to many other trees and plants, bonsai are vulnerable to attacks by diseases and various pests. If you keep your bonsai in excellent health, you can ward of insects who are attracted to dyeing and weak trees. A healthy amount of light, fresh air and clean soil will ensure your bonsai stays healthy and gives you years of enjoyment. Insecticide soap spray is an option, however you should re-apply on a regular interval to prevent attacks from coming back.
Training your Bonsai
Expanding on the training idea of pruning and trimming, bonsai can be further trained using copper wise or hemp rope. The copper wire is rooted at the base of the tree and than wrapped around the trunk and branches, which allows your to train the branches to grow in your desired direction and shape. The wire should be wrapped closely but not too tight and the bends created should not be too extreme as to damage the branch. Once the wire starts biting into the bark, it should be removed. Removal should be done by snipping the wire at each bend, do not un wrap the wire as it can damage the branches and bark.
Soil for your Tree
When discussing watering above we noted that Bonsai trees use free draining soil, which means that it passes the water through and does not retain like typical potting soil. The makeup of the soil allows the roots of your bonsai to breathe freely. Bonsai soil comes in two main types, conifer and tropical mixtures. When you repot your tree make sure to do so with dry soil.
Repotting your Tree
As your bonsai grows and matures it will need to move containers. However unlike most repotting we do not upgrade our pots to larger sizes. When the bonsai is repotted the roots should be trimmed to fit the previous container size. Average time between repotting is 5 years, however it should be checked annually to verify root ball size. When trimming the root ball, do not remove more than 1/5 of the root material. Finally when repotting keep the bonsai out of the sun/light for at least a week.