I looked up this subject and couldn't find anything. I've lived in this house for almost three years, and I just can't figure out why these Periwinkles leaves turn yellow and die off! I never had any problems in other areas of Florida. I know these are drought tollerent, so I don't go over board on water, but I did water twice a week, and even sprayed a few times with liquid iron, and sprinkled with some 6-6-6 once or twice. I have sprayed with copper, and also neem oil, (seperate times not together!)
So I just can't figure out what the problem is. Could it be high alkaline or too acid? No, I didn't have a soil sample...sorry .
Thanks for any help you can spare!!! : 0)