Why Does My First Love Gardenia Drop Lots of Leaves?

Fungal Diseases

• Fungal diseases can cause the leaves of First Love to drop. Root rot, which is caused by fungi that thrive in overly wet conditions, can damage the roots of the plant to the point where the leaves can't get enough nutrients. Eventually, they wilt and drop from the plant. Powdery mildew, which is a fungal infection that attacks the leaves of the plant, also can cause the leaves to drop. Keep the foliage as dry as possible to prevent powdery mildew, and make sure the soil is well-draining to prevent root rot. Containers housing First Love or any gardenia should drain well.

  Cankers, lesions in the wood caused by the fungus Phomopsis gardeniae, can cut off the flow of nutrients enough so that the leaves drop. This sometimes occurs when the plant is wounded and then infected by garden tools. When pruning away diseased branches, sterilize the pruning tools by soaking blades for two minutes in a solution 9 parts household chlorine bleach and 1 part water.

Insect Pests

• Thrips and aphids both commonly infest gardenias, and both can inflict enough damage on First Love to cause leaf drop, as can soil nematodes, which feed on and damage the roots of the plant. The latter are less likely to infect First Love cultivars that are grafted onto Gardenia thunbergii root stock. There is no way for home gardeners to eradicate nematodes from the soil, but if the gardenia's roots aren't too severely damaged, it may survive if given enough water and fertilizer, according to Clemson Cooperative Extension. Gardenias with severely damaged roots should be destroyed, however. If you see thrips or aphids on your plant, however, the best and most environmentally-safe way to get rid of them is to knock them off with a strong stream of water.

Cultural Conditions

• Gardenias are not the easiest plants to grow, and First Love is no exception. Hardy in U.S. Department of Agriculture plant hardiness zones 8 through 11, they are picky about temperatures and may drop their leaves if soil temperatures fall below 70 degrees Fahrenheit, according to Clemson Cooperative Extension. Insufficient light -- the plants thrive in partial or full sun -- and too little or too much water may also cause the leaves to drop. Keep the soil moist -- water at least once a week and more when the weather is exceptionally hot and dry. Finally, gardenia leaves can turn yellow and drop from the plant in response to a lack of iron. This happens when the soil pH is too high -- above 7.0. To prevent this, grow gardenias in soil that has a pH level of between 5.0 and 6.0.

Normal Life Cycle

• If your First Love is otherwise healthy -- there is no sign of insect pests, root problems or fungal diseases on the leaves -- then the leaves might be dropping as a normal result of the plant's life cycle. This often happens in the fall, according to the University of Florida IFAS Extension, when warm days are followed by cool nights. As a result of the temperature changes, the plant's leaves turn bright yellow and drop from the branches.