I have a potted tri coloured buddleia which I got last year. This year its losing its leaves up the stems , its flowering altho they are small in size . I dont no if its root rot or something else ,as I did water everyday for a while when it was really hot but have stopped now .I’ve read of certain problems but cant find any pictures to show you what each would look like .
Certified GKH Gardening Expert
I do see signs of overwatering and disease. It is still the early stages of the disease. I think a few rounds of fungicides will take care of it, but make sure to only water once the soil is completely dry down to about 2 inches. This will not be on schedule, as the climate conditions at the time will dictate how often you will need to water.
Be sure to always check before watering to prevent this in the future. Without treatment, it will not go away, and will progress, so correcting watering habits will not be enough, alone.
Here are some articles that will help: