Gardenias are so beautiful but very difficult to grow successfully indoors.  They are temperamental in care requirements and respond best to cool temperatures, high humidity, constant soil moisture and bright to full sunlight. Those are all quite difficult to provide indoors in the northeast US.

The full growing care instructions are below and you need to follow them all to have success. You will see the soil recipe instructions under "Transplanting". Also, be careful not to use a very large pot -- it should just fit the root ball. These plant really like to be tight in their pots.

Good luck!

Cultural Requirements

Light:

Gardenias need at least 4 hours of direct sunlight a day.

Watering:

They prefer to be consistently moist. In order to reduce excess fertilizer salts in the soil, water with distilled water once a month.

Temperature:

Cool temperatures are preferred, 65° to 70°F during the day and 60 to65°F at night. High temperatures will result in leaf and flower bud drop.

Humidity:

Gardenias grow best with extra humidity. Provide extra moisture with daily misting, as well as setting the plant on a tray of moist pebbles and/or using a humidifier. Use a simple hygrometer to make sure the humidity around the plant is 50%+. Extra humidity is important in keeping down spider mites that thrive under dry conditions.

Feeding:

During the growing season (March through September), fertilize gardenias every two weeks with a dilute fertilizer for acid-loving plants.

Transplanting:

When it is necessary to transplant, use a soil mixture of two parts peat moss, one part sterilized houseplant potting soil and one part sand or perlite.

Propagation:

Propagate gardenias in early spring with 3 to 4" stem cuttings just below a leaf node. Dip the end of the stem cutting into a rooting hormone, place it into a light mix of soil with perlite and keep it moist. Transplant the rooted cuttings into 3" pots with the preferred growing mix as described above.

Maintenance:

To encourage continuous blooming, cut off the faded flowers to just below the leaf node, maintain a cool (below 65°F) night temperature, and feed with a dilute fertilizer with iron every two weeks during the growing season. In addition, keep the humidity level high and prune/shape the plants in early spring to encourage branching and compact growth.

Special Note:

Monitor and treat insect and mite pests as soon as possible. Avoid leaf and flower bud drop by keeping night temperatures cool, providing high humidity and giving sufficient light.

Courtesy of NYBG Plant Information Service