Hibiscus Bud Drop: Where Does the Blame Lie?

Unfortunately, hibiscus bud drops happen every now and then. They are not necessarily caused by hibiscus diseases. The root of the problem is that buds are really sensitive to everything, so the wrong amount of water, fertilizer or sunlight, or any changes in the environment of the plant may cause this problem. Even cloudy weather after sunny days may be stressing enough for the plant to stop blossoming. Of course, it is a shame to see a bud (which you were expecting to unfurl into a beautiful flower) not opening but dropping from your plant, but it is not a reason to be alarmed.

Though black buds are a sign of disease. If you notice blackened buds falling of your hibiscus, remove all the fallen parts from the plant immediately. Changing environmental condition may lessen the disease, but to make a clean sweep of it consider treating the plant with a fungicide.