Have you considered growing the wisteria(s) in tree form? That's how I grow both the Chinese wisteria and the Japanese one. I would never grow them on a trellis or pergola for several reasons:

- they need heavy pruning to flower best and that is difficult to do once you need to climb around at the top of a structure to prune! It's far easier to keep the vine in reach by controlling the height of the 'tree'.

- Chinese wisterias have relatively short flower racemes that produce most of their bloom before the leaves emerge so they display best grown in a more shrubby/tree-like form. Japanese wisterias, on the other hand, have longer flower racemes that have a relatively longer bloom period because the individual florets open in succession from the base of the raceme to the tip. That means most of the flowwering happens with the foliage emerged. So the flower racemes display well dangling from the top of a pergola where the pergola structure holds the foliage back, allowing the flowers to dangle free. But the pruning issue mentioned above means I still prefer to grow the Japanese one as a 'tree', although I keep it 'limbed-up' higher to display the flowers while the Chinese one is branched quite low to the ground..

- root suckers need to be removed/not allowed to climb into the structure; it is easier to identify and remove root suckers if the area around the base of the vine is kept clear. Since many wisteria are grafted plants, root suckers may well be from an inferior seed-grown rootstock that may take a long time to bloom - and produce inferior flowers when/if it blooms.

Wisterias are beautiful plants if grown with care but are monsters if neglected - and most people neglect the pruning since it can be a big chore, particulary in the first 5-10 years. Since a wisteria is almost impossible to kill, be very sure that you are prepared to do the necessary work before planting ono of these beauties!

This picture shows the difference in growing style for my two Asian wisteria 'trees' - 6-year-old Japanese wisteria with 13-year-old Chinese wisteria just finishing flowering in the background:
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