This is the second year I have lost all of my Vincas. I set out beutiful, healthy plants and and before very long I have watched everyone of them die. One day they are standing tall, blooming and the next day your look at them the leaves are starting to roll under, and real flacid. All the ones I've pulled up and looked at them and the stem at ground level has turned brown and is hard. I know the plant can't get nutrients through that. I mix my own potting soil. If anyone has any answers for me I'd appreciate it. I simply love this plant but can't seem to grow it. I also have had some of the same problems with Petunias.

Thanks in advance.