Answer: Wisteria can be so stubborn! You are in very good company--you would be amazed at how many folks have difficulty getting wisteria to produce flowers. Proper pruning can help achieve your goal, as can withholding fertilizer. Too much nitrogen will encourage lots of growth, at the expense of flowers.
All through the summer, prune out the tips of all new shoots when they reach 12" long. In the winter, shorten the shoots again so that about 6 buds remain on each shoot. Cut away all suckers that appear at the base of the plant.
Sometimes root pruning around the drip line of the vine will stimulate the flowers to form for next year. If it were planted in the ground, you'd just dig down one foot deep all around the drip line, breaking any roots you meet. Since yours is in a container, you may want to unpot it, massage the roots a bit, then repot it in fresh soil.
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