Answer: Although it sounds suspiciously like your gardenia is afflicted with a fungal disease, I can't say for sure. Leaf drop can also be caused by improper soil pH (gardenia require 5-5.5pH - on the acid side.) Since you've grown them successfully before, I trust you know what you are doing, but I'll just mention a few key things. You know moisture is one of those things. Another fresh, moist air, circulating freely, especially during the winter heating months (a humidifier is good for you, too!) Try using an acid houseplant fertilizer from your local garden center. That may turn it around.
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