Beloved for their intoxicating fragrance and attractive, waxy, creamy-white flowers contrasting beautifully with their shiny, leathery, dark green leaves, Gardenias are irresistible evergreen shrubs or trees. Native to the tropical and subtropical regions of Africa, southern Asia, Australasia and Oceania, Gardenias may be fussy and quite temperamental in their cultural needs.
If your Gardenia's leaves turn yellow and drop, aside from the normal aging process of its leaves, this may be caused by any of these reasons:
- Over-watering or under-watering: Gardenias need at least 1 inch of rain (or equivalent watering) each week. Keep the soil consistently damp but not soggy. Don't let the soil dry out and don't over-water your Gardenias
- Poor soil drainage: Make sure your Gardenia soil is moist and well-drained.
- Insufficient light: Although a Gardenia plant prefers full sun, some shade is appreciated during the warmer months of the year or its leaves may scorch and its buds may fall off if they get too much sunlight. In hot climates, Gardenias grow best with morning sun and afternoon shade. In cooler areas, they can tolerate full sun, especially if their roots are covered with organic mulch. Gardenias growing in containers need bright light or filtered shade with no direct sun. Gardenias grown indoors should receive at least 6-8 hours of direct sunlight through a sunny window.
- Unusually cool weather: Gardenias perform best in day temperatures of 65-70°F (18-21°C) and night temperatures of 60-65°F (15-18°C). Lower temperatures may cause leaf yellowing and drop.
- Nutrient deficiencies: Gardenias like soil that is rich in nutrients. Add plenty of organic matter to the soil such as peat moss or manure to enhance the growth of your plant.
- Iron Chlorosis: Iron is a key nutrient that is used by plants to produce chlorophyll. Gardenias prefer acidic soils with a pH between 5.0 and 6.0. If your soil pH is too high (above 7.0), the iron may not be available to your plant.
- Root Rots: Various fungi cause a decay of Gardenia roots. This disease stems from wet soil conditions such as poor drainage and over-watering.
- Nematode feeding: Various nematodes (microscopic worms) feed within plant roots. There are no nematicides available. If your Gardenia is severely affected, it should be removed and destroyed.
To grow your Gardenia with success, make sure you follow these guidelines.