The flowers of the gardenia jasminoides, now called Gardenia augusta, are traditional symbols of the Deep South. The shrubs are often planted near a patio or deck where the fragrance of the flowers can be enjoyed. The white waxy blooms are excellent cut flowers and will perfume a whole room with their strong fragrance.
Gardenias are evergreen shrubs with a rounded form that grow 6 feet tall and wide. The glossy dark green leaves provide a backdrop for the white flowers, which bloom for several weeks from mid-spring to early summer. The flowers turn creamy white as they age.
Gardenias are hardy in USDA zones 8 to 10, and should be grown as houseplants in colder areas. They should be planted in the fall or spring in the sun or partial shade. They prefer acidic soil (pH 5 to 6) high in organic matter that is moist but drains well.
Do not hoe or till soil around gardenias, as they resent having their roots disturbed. A fertilizer for acid-loving plants should be applied in March and June according to the manufacturer's directions. The best time to prune gardenias is after they finish blooming.
Start stem cuttings of gardenias in moist soil in the summer. They can also be started in late winter and kept at a temperature of 80 degrees.
Although gardenias are not susceptible to many diseases, numerous sucking insects attack them. Aphids, scale insects, spider mites and whiteflies cause leaf damage and excrete honeydew. Sooty mold is a fungus that grows on the honeydew and forms fuzzy black patches on the leaves. Using an insecticidal soap according to the manufacturer's directions can control the insects and the sooty mold.
Bud drop on gardenias is caused by low humidity, over-watering, under-watering, low light levels or high temperatures. Chlorosis (yellowing) of the leaves is caused by alkaline soil (pH 7 or above) and can be treated with an application of iron chelate, following the manufacturer's instructions.
Gardenia augusta is native to China, Japan, Taiwan and other subtropical regions in the Eastern Hemisphere. It was originally called Cape Jasmine because people thought the plant was native to the Cape of Good Hope in South Africa.