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?
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Here are some links that will help you pinpoint the issue.