30+ Azalea Turning Brown. If the azalea flower itself is the only part of the plant that appears to be suffering and turning brown, the azalea has ovulinia azaleae, or petal blight. They'll also turn dark colors in winter.it may just be winter color.
You could also have an issue with the soil ph not being acidic enough.
Azalea turning brown ok so what wrong with my azalea it looks even worse now the leaves are turning brown and it not blooming can see where yellowing leaves and browned tips, although i am not an expert, seem often to indicate over watering but it is reckoned impossible to over water a spider. If the leaves on your japonica bush are turning yellow, you might have an issue with lace bugs that are eating the bush. These nutrients are available at garden supply stores. I had an azalea which was doing very well, repotted ~ 6 months ago ( i cant remember exactly) and in the past month all the leaves have turned brown and the plant is failing.