Hi! I brought a perfectly healthy and flowering Gardenia last fall. It was healthy all winter and then got way over watered in March. It grew white mold on the surface of its pot soil. The leaves turned yellow and they dropped 50% off. I removed all the visible mold, dried out the plant and used cinnamon in the pot to combat any fungus. Now the plant has still not recovered even though outside. New leaves grow in mal-formed and any flower buds get crispy and black and break off. There is new growth and the plant is surviving but I can’t figure out how to cure its problem. I’m guessing it’s maybe root rot of something like that? Pls advise:) Thank-you!
Thank you for contacting Toronto Master Gardeners about your Gardenia (Gardenia jasminoides). Gardenia plants are high maintenance and require specific conditions to grow and bloom well. Distorted leaves and flower buds dropping could be caused by a number of different stress factors including: temperature swings, over/under watering, over/under fertilization, low humidity, soil conditions, very hot, dry weather or a pest infestation (aphids, thrips, mites). Tips previously published by Toronto Master Gardeners for the proper care of your gardenia (soil, fertilizer, light, watering, and temperature) can be found at Gardenia tips.
You didn’t mention what soil you used for repotting your plant after it was over watered. Gardenias do best with slightly acidic soil – look for soil suitable for Azaleas and Rhododendrons. Gardenias also thrive in bright indirect light (direct sunshine can burn the leaves while too much shade may result in buds dropping). Check for insect infestation on the leaves and flower buds. Once you’ve ensured you’ve met all the growing requirements for this “diva” of a plant, give your plant some time to recover from its over watering and adjust to its new outdoor conditions.
A good resource for Gardenia diseases, including control measures and a list of appropriate fungicides (when required), can be found at this link: Gardenia Diseases.
Another useful publication, with photos, that you may wish to consult is Common Indoor Plant Problems.
June 7 2021