Problems with Gardenia
For the past couple years when I brought my potted gardenia plants inside they did fine for about a month or two and then they started having problems. The deep green color of the leaves starts to fade to pale green and they start to grow some white things on the branches. The white things actually look like little tiny cotton balls about the size of a fertilizer pellet.
Pale green leaves can be a result of low light, high soil pH, and feeding by mealybugs, the white fuzzy things on the branches. Move the plant to the sunniest window available or supplement low light situations with artificial lights. Apply a dilute solution of acidifying fertilizer labeled for use on flowering plants. Use distilled or rain water, melted snow or water from your dehumidifier to avoid "sweetening the soil if your tap water tends to be alkaline. Now treat the mealybugs. Use a cotton swap dipped in alcohol. Touch each fuzzy mass. The alcohol dissolves the covering and kills the insect hidden below. Spray the plant with Neem (insecticidal soap can damage gardenias) to kill any immature mealybugs that have not yet developed a fuzzy coat. Monitor and repeat as needed. It usually requires several treatments to get these insects under control.