All trees grow outdoors. Trees which normally grow in the tropics and warmer climates, can in cold countries be grown indoors. Examples are Ficus, Jade, Chinese Elm etc.
Light is important for the trees survival and to make sure you need to find out what specie you have and then what position it prefers, shade, partial shade, full sun. For example Japanese Maple prefer partial shade.
Watering has to be right, don’t over or under water. The bonsai soil should only be soaking wet when the tree is watered. After that the soil should be moist and water again when the soil is moist on the dry side. During very hot summers, I have had to water twice a day. In Japan the bonsai nurseries water a number of times a day. Due to excessive heat the small amount of bonsai soil in the pots dries out quickly, so keep an eye on watering.
Feeding is also important to maintain the health and vigor of the tree. I used balanced feed 10:10:10 most of the time. If you cannot get this strength, then get the next higher one and dilute it down. I also use Chicken Pellets, these smell, but are very low cost and produce excellent results.
Pruning is essential to maintain the shape of the tree and if you use clip and grow method, you are styling the tree as it grows. Pruning during the growing season also helps keep the tree small instead of letting it become a bush. Some basic rules to follow are to remove any growth growing inwards or towards the trunk, also remove any growth growing downwards so that there is no growth on the underside of the branches. Also remove any growth going straight up.
Wiring techniques are used to move branches into desired position and also create movement in young trunks and branches.
Repotting is important and should be done in spring. The roots are combed out and a third of the roots are removed. The tree is kept small by pruning the new growth and also by root pruning at repotting time. Deciduous trees need repotting every two years and the evergreens like the pines and junipers every eight to ten years.
Above is bare minimum to get you going.
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