Bonsai trees are not naturally dwarf varieties. They are ordinary plants which have been cultivated and trained to produce the dwarf look that you see in the stores. This takes time and skill, which explains the high price of the specimens you see. Many specimens can live to be over 100 years old and still fit on a table top.
WATER: Bonsai are fascinating to grow but they are a lot of trouble. Moist air is essential. Stand pot in a pebble tray or mist leaves occasionally. The soil must be kept moist (but not wet) at all times. This may call for daily watering. The best method of watering is immersion but overhead watering is generally satisfactory.
TEMPERATURE: Average temperature is OK but keep them away from drafts and heaters.
LIGHT: Most types require bright light but keep them away from direct sunlight as they may get sunburn.
Feed every 6 weeks. Repot in spring every 2 years. In the case of a mature, trained plant, some of the old soil is removed and no more than 1/3 of the root growth is cut away. It is repotted into the some container with fresh well-drained soil.
These specialty plants are available in oblong resin trays, however, by special order they can be obtained in ceramic containers in larger sizes. A note of caution: these get very expensive as they get larger.