Gardenias are evergreen shrubs, but drop leaves as part of a normal process. However, sudden leaf or bud drop is undesirable. Drought, stress or excessive heat or cold can cause bud or leaf drop. Gardenias produce flowers only within a relatively narrow temperature range and will drop buds and fail to produce blooms when temperatures are high or low. Leaf or bud drop may be caused by changes in soil moisture, weather, or nutrient deficiencies.
Solutions
Provide plants with good cultural care, especially proper watering. Use mulches to conserve water and decrease soil temperature fluctuations. In cooler coastal areas, plant in full sun. In hot inland valleys, plant in filtered shade.
