Why people have pergolas

I ain't proud of much but I sure am proud of this Wisteria on a roof deck in Manhattan. Wisteria flowers don't happen like this all by themselves. Most Wisteria's provide a half-assed flower show or no blooms at all...which is alright because they have nice foliage. BUT if you want this to happen all you need it sun and a good pruning in late LATE winter or very early spring.