Hardy hibiscus is about 2 1/2 feet tall. Leaves at the tips are curling inwards and are turning black. I have other hisbicus plants nearby and they are healthy so far. Does anyone know what this is and what I can do?
Do you see any insects on it? There could be scale or aphids on it and their excretions of honeydew end up causing sooty mold to form on the leaves (which would then put a black coasting on the leaves).
Should read: black "coating" not "coasting". ;-)
Look underneath the leaves and see if there are insects. I'm sure if you have sooty mold, you have insects of some sort.