What is happening to my rosemary plant?
The leaves are turning brown and black please help.I am from India.
Certified GKH Gardening Expert
I'm afraid that the clay soil the plant is in will not be very suitable for a container application. It has a tendency to stay, either, too moist or too dry. This can lead to fungal infections resembling what you are seeing on your plant.
You will need to change the soil to a suitable potting soil, or at least add compost to the clay. I do not recommend the latter, as using clay soils in containers is quite a chore.
Once you get it into a suitable soil, then you can begin treatment. This will be a fungicide.
These articles will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm