QuestionsHow to growTrees and ShrubsFeedingNonflowering clematis 0 Vote Up Vote Down Hilary Brady asked 14 years ago I have two white clematis. Both have an abundance of leaves but no sign of flowering. 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 6 years ago There is time still if they are summer-flowering. Over-feeding can cause a lot of foliage, sometimes at the expense of flowers.