Clematis not developing
I grew clematis in a slightly acid heavy soil successfully for years. Since moving to a light, neutral soil four years ago I have planted several clematis. The established one from my old garden still flowers but has very little new growth. Others have barely survived the winter and just manage to replace the little growth they had when first bought before struggling during the next winter. Two plants, usually easy to grow President and Montana bought as fairly large plants died. I plant them with extra compost and shade with a small plant. They are in a variety of positons , mainly South East facing. What should I feed the plants with to encourage strongergrowth?