Answer: Your Korean Snow Rose is Serissa foetida. These small shrubs are much loved as bonsai for their tiny flowers which may occur 2-3 times yearly, gnarled trunks, and naturally miniature leaves.
Serissa is a notoriously fussy bonsai. The good news is that they aren't that hard to keep alive. But considering that most people buy Serissa on impulse because the plant is so spectacular at the store, the bad news is bad indeed. The plant will generally drop its flowers within a day or two. Then the plant will drop its leaves. If the grower doesn't panic (and many Serissas are inadvertantly killed by panicing beginners who respond by drastically over/underwatering the plant) the plant will soon regrow its leaves. A power struggle then ensues. The grower soon discovers that the Serissa drops its leaves if it has too much water. Too little water. If it's too hot or too cold. If it's moved, or there is a shift in lighting or temperature.
Lighting: Partial sun. If kept indoors, needs grow lamps for 12 hours daily. Too little light will result in leggy growth.
Some growers take them outdoors in summer and bring them in when temperatures drop to 50F. Ideal winter temperatures range from 50-68F. More important than the actual temperature seems to be two factors: the plant dislikes a sudden change in lighting (many die from lack of light when brought indoors) and individual plants may be show different hardinesses (a Serissa grown outdoors from youth will withstand a greater variation in temperature than a Serissa purchased from a greenhouse). If brought indoors, do not position this plant near a heat source, or it will lose leaves. If kept outdoors year round, it will drop leaves as the temperatures become colder.
Hope this at least begins to answer your questions on your bonsai! Now that you know the botanical name of your plant, you can do a thorough web search.
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