How do I get rid of and control black spot on my gardenias?
Black Spot Mildew on Gardenias
Certified GKH Gardening Expert
I would recommend using neem oil. It will treat the fungus with the added bonus of keeping pests away, which gardenias indoors are also prone to. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm