The Gardenia jasminoides is really considered an ornamental shrub. It has very dark and shiny leaves. Their flowers are white with an exquisite fragrance that makes this plant very popular. They bloom from mid-spring into summer. Gardenias can be either an indoor or outdoor plant depending on your climate.
Plant gardenias in United States Department of Agriculture (USDA) hardiness zones 8b through 11. Test your soil’s pH balance before planting. The pH level, or measure of acidity in the soil, should be between 5 and 6. Plant your gardenias in the spring or fall. Space them 3 to 6 feet apart. The hole needs to be as deep as the root ball and wider. Once you place the plant in the hole, fill in with half the dirt and then water. Once the soil settles, fill the rest of the hole with dirt and water again.
Gardenias can be potted plants in areas outside their recommended zone. They make great deck or porch plants. Put them where you will be able to enjoy their fragrance. In the winter. the pots must be brought in and kept in certain conditions.
The gardenia is one of the more care-intensive flowers. Gardenias have very particular growing needs and it takes work to achieve these. They are very popular in the southern United States, where severe cold won’t hurt them. They need temperatures of 68 to 74 degrees Fahrenheit in the day and about 60 in the evenings. The outdoor variety needs partial shade. Fertilize monthly between April and November with an acid fertilizer. Deadhead after flowering and check periodically for insects.
Gardenias prefer full sun if kept indoors, and maintaining humidity is the biggest issue with an indoor gardenia. Some horticulturalists recommend misting the leaves, but others disagree, arguing it will cause spot fungal problems. Loose, well-drained organic soil is recommended instead.
The biggest problem associated with gardenias is “bud drop," when flower buds fall off just before blooming. Common causes include low humidity, over-watering or under-watering, temperature and light, or change in plant location.
Gardenias are susceptible to several diseases. Canker is one of the most common. It is identified by a swollen main stem at or below the soil line. The bark also develops cracks in the affected area. Affected plants stop growing and die slowly. Destroy all diseased plants to prevent its spread. Rhizoctonia leaf spot is another common disease. The leaves become infected with a tan or brown spot. The affected leaves should be destroyed and the plant should be replanted in fresh soil.
Many other disease affect gardenias. Check your local nurseries or consult a plant guide book for more information.
It is believed that gardenias originated in Asia, in the western parts of China, Japan, and Taiwan. They are said to be named after Alexander Garden, a physician in Charleston, South Carolina, during colonial days.