I live in Florida. I have a gardenia plant in the front yard that gets a lot of sun. Have had it for 2 years. I get tons of buds on my plant but only about 4-5 blooms. Last year I got black stuff (fungus/mold) on my whole plant, so I sprayed with soapy water. All my buds fell off and leaves got yellow and fell off. It's doing it again this year, so I sprayed again with soapy water. Now my leaves are turning yellow and falling off and my buds are falling off too, AGAIN!! I also notice my neighbor's don't have this problem. Theirs are green and have plenty of flowers. Don't know what to do!
Certified GKH Gardening Expert
This is sooty mold. It happens when the plant gets a pest infestation. I would recommend using neem oil, as this will get rid of the sooty mold fungus and kill the pests. Here is some articles that will help you: https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm, https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm