I'd caution you about Wisteria and it's utterly invasive nature! It will crawl onto/into the house every chance it gets. It'll crawl into cracks in clapboard, shakes, and even vinyl! It's been known to get into foundation cracks and cause structural damage! Be sure to prune regularly and if you see any little vines making their way into/into the house, cut that guy back and hope his friends were watching so they got the message! LOL! As far as how many to plant, my suggestion would be start with 1, you can always add more later. Wisteria grows super fast so I wouldn't worry about it not covering the patio pergola. I've grown the Blue Moon variety and not only is it a super fast grower, but it's flowers are truly beautiful! I absolutely love it! Hope this helped, good luck!
I'd caution you about Wisteria and it's utterly invasive nature! It will crawl onto/into the house every chance it gets. It'll crawl into cracks in clapboard, shakes, and even vinyl! It's been known to get into foundation cracks and cause structural damage! Be sure to prune regularly and if you see any little vines making their way into/into the house, cut that guy back and hope his friends were watching so they got the message! LOL! As far as how many to plant, my suggestion would be start with 1, you can always add more later. Wisteria grows super fast so I wouldn't worry about it not covering the patio pergola. I've grown the Blue Moon variety and not only is it a super fast grower, but it's flowers are truly beautiful! I absolutely love it! Hope this helped, good luck!