Bonsai trees need care similar to any other plant below is a basic outline of care for a Bonsai tree.
Many people do not realize that most bonsai trees should be kept outdoors year-round. The few exceptions are the non-traditional tropical trees which need to be kept inside if you are not in a tropical environment.
Outdoor bonsai should be positioned where they will get six or more hours of light each day.
Indoor bonsai should receive two to four hours of natural or artificial sunlight. For inside bonsai full-spectrum, fluorescent can provide the necessary light levels, but the tree needs to be placed close to the light.
More trees die from a lack of water or low humidity than anything. The soil used to raise bonsai is normally porous soil that drains well. The type of soil, as well as the shape and design of the pot, will affect quickly the soil dries out. Different tree types will require different amounts of water to thrive. You will need to research your specific species of tree for a general guideline and then closely monitor how the tree grows to determine if it is being watered correctly. If you take your pot and place it on top of some rocks in a tray full of water this will help increase the humidity around the tree and will aid in its growth. Along with normal watering about once a week you should fully submerge the bonsai tree pot until no more bubbles escape from the pot or the soil.
Pruning serves a dual purpose in the care of bonsai trees. Pruning removes branches that clutter and hamper the aesthetic design of the tree. Pruning is also used to direct and control the growth of the tree. You will also have fine pruning such as pinching and leaf pruning to help encourage branching. Always remember when you are pruning your bonsai that you can always remove something later, but it is very difficult to put it back after you have cut it. So if in doubt leave it for now. You should start with a light pruning then give it two or three weeks and wait for the bounce back to decide if you need to do more. Pay special attention to developing the trunk, anywhere on the trunk that a branch is allowed to grow will thicken. When pruning you need to keep the top and bottom (roots) balanced for optimum results.
Your average bonsai will need to be fertilized once or twice a month. You should only fertilize during the normal growing season. Use a water-soluble fertilizer and apply it when the soil is already wet.
Proper soil choice is critical for optimum bonsai tree care, the soil affects the roots, feeding, and watering of your tree. The size and shape of the pot affect both the appearance and the growth and health of the bonsai. As a rule of thumb, it is about 3/4 as wide as the tree is tall and about half as deep. The height of the pot should be roughly the same as the diameter of the trunk. Bonsai soils are designed to optimize drainage. They are usually a mix of coarse sand or gravel with peat or bark added for an organic element. Different trees will need various ratios of grit to humus. Usually, deciduous trees need about 70% humus and 30% grit while evergreens will thrive better with 30% humus and 70% grit.
Re-potting is a critical element of bonsai care. It is crucial to help keep the roots and top of the tree in balance. Bonsai trees should be re-potted every two or three years. When you re-pot the bonsai you need to trim the roots. You will normally want to remove about 1/3 of the root ball. You need to trim all away around the ball to keep it in balance.