There was a mature wisteria on the south -facing side of our house when we bought it 7 years ago. Since then it has continued to grow vigorously and in the last 3 years, especially, bloom profusely. This spring it also bloomed well but the growth of the foliage has been lackluster since then – and we need the foliage to provide shade. Every year I have pruned regularly, but only excessive new growth. Is it time to cut back strongly to encourage more vigorous growth?
Here are some links that will help you pinpoint the issue.