Light

• Light-loving gardenias bloom best in full sun indoors. They grow in dappled shade outdoors, but buds and petals turn brown with too little light.
  
  

Moisture

• Gardenias will not tolerate wet roots but need constant moisture. They drop their buds or flowers turn brown if not kept moist. Plant gardenias in well-drained soil and water them every other day in the summer. If you mulch the soil around them, water every third day.
  
  

Temperature

• Gardenias tolerate frost, but need a summer daytime temperature of 73 degrees with nighttime around 60 degrees. They are sensitive to changes. Buds turning brown or drop after bringing them home from the greenhouse are common.
  
  

Pests

• Gardenias are a favorite of spider mites and thrips, which turn flowers and foliage brown. Wash them off with soapy water as soon as you see them and repeat the process in two weeks. Brown spots are leaf spot fungus. Prune and destroy affected areas.