Place the plant where it gets plenty of bright, indirect light. Eastern and southern exposures are best. Some direct sun is acceptable, especially in winter.
Water from the bottom when the soil feels dry. This might be every other day in summer. Probably less often in winter. If possible, use rain water or distilled water. Be sure the pot drains well and do not let it sit in the drainage water.
Gardenias benefit from outdoor temperatures and humidity in summer. A sheltered, semi-shaded location is best.
Apply fertilizer formulated for acid loving plants monthly at half strength in summer.
Gardenia flower buds are very susceptible to dropping off before blooming. Several things can cause premature bud drop: over or under watering, sudden temperature changes, night temperatures over 70° F, and insufficient light. Lack of adequate light or allowing the soil to dry out excessively may also cause some older leaves to turn yellow and drop off.
Some pruning and training will be needed to maintain the plant's bonsai form.