In the spring, Gardenia jasminoides will delight the eyes and noses of many, with their large waxy white flowers and beautiful fragrance that can fill the yard or drift in to the house through an open window. Gardenia jasminoides is known by some other names such as gardenia, gardenia augusta, cape-jasmine, or august beauty. This plant is an evergreen with dark, glossy green leaves, which makes it an attractive pot plant.
Gardenia jasminoides is a native plant of Japan and southern China. Gardenias are hard to grow outdoors for people living in U.S. Department of Agriculture Zones eight through 11. If you live in colder zones, then you can grow this plant in a container indoors.
A gardenia growing outdoors can grow to heights of 6 to 8 feet, with a spread of equal length. But if the gardenia is grown indoors, it will stay on the smaller side, reaching only 1 to 3 feet in height. Gardenias grown indoors need special care to ensure your growing success.
The Right Temperature
Gardenias grow best when the daytime temperatures remain between 65 to 70 degrees Fahrenheit. When evening comes, the temperatures should be between 60 and 65 degrees Fahrenheit. If you want to encourage the gardenia to bud and then bloom, then maintaining these temperatures is important. If your gardenia stays in a room that is too hot or too cold, the flower buds will not form.
Sunlight
When growing gardenias outdoors, you need to find a location that is partly sunny or partly shady. Gardenias growing indoors, find a bright window that offers protection from the hot midday sun. A south-facing window is best as long as there is a light curtain between the gardenia and window to help diffuse the light. Otherwise, it will be too hot for your gardenia and the leaves could burn. During the winter months, when the skies are dark and cloudy, you may need to provide artificial lighting.
Humidity
Gardenias grow best when the conditions are humid. For gardenias growing indoors, it is important to raise humidity. You can do this in several ways. A humidifier placed in the room where your gardenia is growing helps, or you can fill a bowl with rocks. Pour water into the bowl keeping the water lever just below the top of the rocks, and then place your gardenia pot on top. The pot should never sit in water. Mist the leaves of the gardenia several times through the day.
Watering
To test the soil for moisture, insert your finger to the second knuckle into the soil. If the top two inches of soil feels dry it is time to water. When you water, use soft water otherwise the leaves may turn yellow from chlorosis. To control this problem, add iron sulfate or iron chelate to the potting soil. Read the label directions for the proper way to apply. You will need to do this one or twice a week for 30 days.
Fertilizer
Gardenias need fertilizer to grow healthy and strong. Choose an acidic fertilizer for your indoor and outdoor gardenias. If your gardenia is growing outdoors, you will need to feed it in the early spring, before the plant flowers. Feed the gardenia a second time early in the summer. However, if your gardenia is a houseplant, fertilize them every other week, beginning in the spring and continuing until the fall.
Dormancy
When the plant enters dormancy, pinch off the stems tips. This encourages the plant to grow bushier and it encourages more blossoms to set on.
Pests
Check for aphids and spider mites. These insects are small and often hide underneath the leaves. If you notice, the leaves are turning yellow, curling, or if there are holes in the leaves, then you probably have a pest problem. Spray the plant with insecticidal soap. You can buy insecticidal soap at most garden supply centers, or online. Read and follow label directions for proper usage.
When you are pulling weeds from around the outdoor gardenia, do so carefully. The gardenia’s roots are shallow and can damage easily. Many gardeners place a 2 to 3 inch layer of organic mulch to keep the weeds from growing as it helps the soil to maintain moisture.
Repotting
Repot the gardenias growing in pots once every two to three years. Refill the pot with acidic soil that has a pH level of 5 or 6 for best results.
Sources:
AA Florist: Gardenia
The Garden Helper: How to Grow and Care for Gardenia Plants
“The Houseplant Expert”; Dr. D.G. Hessayon; 1980
“House Plants: A Complete Book on Plant Care”; Linda Timko Gonzalez; 1975