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Common Name: gardenia
Type: Broadleaf evergreen
Family: Rubiaceae
Zone: 8 to 11
Native Range: China, Taiwan, Japan
Height: 5 to 6 feet
Spread: 5 to 6 feet
Bloom Time: Seasonal bloomer
Bloom Color: White
Bloom Description: White/ivory
Sun: Part shade
Water: Medium
Maintenance: High
Flowers: Showy Flowers, Fragrant Flowers
Leaves: Evergreen
Uses: Cut Flower
Culture
In their native range, most gardenias are fairly adaptable shrubs tolerant of sun or semi-shade, and do best in a well-drained, humus-rich, acidic soil. Fall or spring is the best time for planting in warmer climates. Place in light to moderate shade, preferably with minimum competition from tree roots. Gardenias resent root disturbance. Use fertilizer for acid loving plants, and use iron compounds. Add plenty of organic matter, such as compost or ground bark to as large an area as possible. Mulch plants instead of cultivating. A good time to feed gardenias in these warm areas is mid-March, using an acid plant food, fish emulsion or blood meal. Fertilize the shrubs again in late June to encourage extra flowers on everbloomers or faster growth of young shrubs. Do not fertilize gardenias in the fall. Doing so will stimulate tender growth. Prune shrubs after they have finished flowering to remove straggly branches and faded flowers. Water gardenias regularly. Drip irrigating the shrubs will keep water off the foliage and blossoms and prevents leaf spots.
Cape jasmine, as it is sometimes called, is more commonly a container plant in conservatories and greenhouses in colder climates but it can be placed outside in warmer months. Grown indoors, these plants need bright light, moderate temperatures; cooler during dormancy, average to high humidity and well-drained, acidic soil. Water moderately, using room temperature water, when possible. Do not allow soil to dry out. Prune after flowering to maintain the plant’s shape and remove faded or brown flowers as they appear. Fertilize from March to August with a mild acid liquid fertilizer.
Noteworthy Characteristics
Common gardenia or cape jasmine is an evergreen shrub with glossy, dark green foliage 2 to 4 inches long and generally in whorls of three. The flowers are terminal or axillary, funnel shaped with 5 -12 spreading lobes to 3 inches across, white to ivory, strongly fragrant and often grown in double-flowered forms.
Problems
Problems include powdery mildew, leaf spots, dieback, anthracnose, sooty mold, whiteflies, mealybugs, scales, aphids and spider mites. These insects are often serious pests. Hard water, lack of iron or too alkaline soil will produce yellow leaves. The loss of buds or black leaf tips are usually due to changes in temperature or amounts of water. Temperatures below 60°F can produce malformed buds.
Garden Uses
In the St. Louis region, gardenias are grown as pot or larger container plants. They grow well in greenhouses and conservatories, but can also thrive when placed outdoors during the summer months and returned to moderate indoor temperatures in the fall. They are prized for their large, very fragrant flowers and are quite often given as gifts to gardening enthusiasts.