Gardenia jasminoides or Common Gardenia or Cape Jasmine is an evergreen shrub, which grows to a height of 2 to 6 feet. Spread is about the same. The foliage of well-fed shrubs is glossy, dark-green, 2 to 4 inches long and half as wide. Depending on the cultivar, the flowers can be either single or double and up to 4 inches in diameter. They are waxy, white and very fragrant.
Gardenias require considerable maintenance. Fall or spring is the best time for planting. Plant in light to moderate shade, preferably with minimum competition from tree roots. Gardenias resent root disturbance. They also grow well in pots.
Gardenias prefer acid, moist, well-drained soils. A good time to feed gardenias is mid-March, using an acid plant food, fish emulsion or blood meal. Feed 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, which may be killed if the temperature in winter drops below 15 degrees. Gardenias are cold-sensitive and during severe winters can be killed to the ground in the Upstate. Often they regenerate in spring.
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. Regular watering is necessary after blooming also to keep the plants in good condition and able to withstand winter weather.
The gardenia flowers are highly fragrant. They open over a long period of time, from May through July and make great cut flowers.
Hardy zone 9b-10
Sow 1/8" deep at 75 degrees F. Keep moist and damp by covering the pot with a plastic sheet. Germination occurs between 21 - 60 days. Gardenias should be planted in well conditioned soil containing peat moss and compost Cultivating around the plants may damage their shallow roots, so the plant should be mulched with 2 to 3 inches of wood chips, sawdust or ground bark to keep the soil moist, cool and weed free. Feed the plants every three weeks during the growing season with a rhododendron-azalea food, or acidifying fertilizer. (Miracid)
Proper temperatures are necessary for a gardenia to bloom. This is the most critical aspect. Flower buds will fail to form if day temperatures are higher than 70degrees or night temperatures are over 65 degrees or less than 60 degrees. The ideal temperature ranges would be 65 to 70 degrees during the day and 60 to 62 degrees at night