Gardenias need very high light for more than four hours daily to grow well and flower. Night temperatures must be between 40 and 60 degrees Fahrenheit to set buds. They grow best in acidic, evenly moist potting mix. Never let these plants dry to wilting; they will not recover.
Gardenias will thrive in 50 to 60 percent relative humidity and should be fertilized every two weeks from March through August with a water-soluble, high nitrogen, acidic fertilizer. Use a potting mix with that drains well.
Gardenias occasionally attract pests including mealybugs, spider mites, whitefly and scale.
For "Greenhouse whitefly" refer to message number 1448.
For more information, see the following Colorado State University Extension fact sheet(s).
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Updated Monday, February 17, 2014