Answer: The pruning would be similar, except that you are training it to one "trunk" and are keeping it short in an "umbrella" style. It should be trimmed often during the summer to maximize the number of growth tips and to keep it in control. Cut it back to only three or four buds starting after flowering season. Be careful you are not over supplying it with nitrogen. Some wisterias are very slow to come into bloom, an average might be about 8 years or so but 20 is not unheard of either. Other reasons for reduced bloom includes lack of sunlight, and a major cause of no bloom is spring frosts that kill the flower buds just as they are about to open. If your plant is in a frost pocket that might explain the problem.
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