Basic, slow growing bonsai trees need little in the way of pruning and styling. With proper light, water and fertilizer, these trees can grow beautifully for many years. However, if you are trying for an advanced style, your trees need more training and care. With some trees, such as Japanese dwarf junipers, initial wiring for shape can take several weeks or months. Once wired, your tree may need to be re-wired every three to six months to prevent bark damage as the new shape "takes" in the wood.
Water your bonsai regularly. The amount of water will depend on the type of tree. Allow the top 1/4 to 1/2 inch of soil on trees such as junipers to dry out. Other trees, such as maples, should always be moist. You can water from the top or submerge it. If you water from the top, water the plant several times over a 10 minute period to make sure that so all root areas have adequate water. If you submerge your tree, put it in a sink or pan up to its trunk for about 10 minutes.
Fertilize your bonsai with organic fertilizer mixed at half the strength directed for flowering plants once every two to four weeks. Bonsai trees grow in a small amount of soil, and this soil needs frequent fertilization during the growing season. Do not fertilize your trees when they are dormant.
Prune your bonsai regularly. Japanese style bonsai are based on the Zen concept of design. Remove any branches that aren't necessary to the form of the tree. By regularly pruning back leaves, the trunk of your tree will increase in size.
Keep your tree in ideal light for the variety of tree. Many Japanese bonsai masters keep trees outside and only bring them inside for display for a few days at a time. Too much light can, for example, cause a yellowing of the leaves on some junipers. Too little light can cause a tree to die. Check with a nursery for light requirements for the type of bonsai you are growing.