Containerized gardenias bought from a nursery do not need to be replanted unless their roots are growing out from the bottom of the pot. In this instance, repot in a larger container. Use a commercially prepared, sterilized potting soil mix, or a slightly acidic medium enhanced with peat moss. A half and half mix of sand and peat moss works well. Aim for a pH close to 6.0 and fertilize to increase acidity if necessary. Water thoroughly after planting and keep the gardenia in a stable environment.
Gardenias can be propagated fairly easily from cuttings. For best results, take cutting in June, July or August. Keep root cuttings moist by misting them or keeping them in a pot covered by a plastic bag. Use a rooting medium that is a commercial gardenia potting mix, or a half and half mixture of sharp sand and peat moss. Gardenias can also be germinated by seed, though this is a slow, erratic process.
Place indoor plants in a bright, sunny location where they can receive at least half a day of direct sunlight. Gardenias prefer temperatures of about 60 degrees Fahrenheit at night and 70 to 75 F during the day. Water regularly to keep the soil moist to the touch. Do not allow the soil to become "bone dry." Fertilize regularly during the growing season, following all instructions. Do not overfertilize, as this leads to an over accumulation of salts in the soil.
Gardenias are subject to a host of sap sucking pests, many of which may be found on the underside of foliage. Common indoor gardenia pests include whiteflies, thrips and spider mites. Spider mites may be washed off with a direct stream of cold water, or with an insecticide. Whiteflies and spider mites may be controlled with an insecticidal soap or insecticide. A horticultural oil such as neem oil can also be effective in controlling pests.