The wisteria on my arbor over the deck is in full bloom now and I love it. It is this beautiful for a week and a half or so, and then, daily, snows purple blossoms all over the deck. It's a mess, but worth it for the time we have this beauty right outside our back door.
However, perhaps this wisteria can be classified as a parasite or a virus; it is trying mightily to destroy the structure on which it lives, as you may be able to see from the photo below. Look at where the horizontal beam is no longer attached to the support post. We (That's the royal we- what I really mean is dh ) have to figure a way to muscle it back up and a way to fasten it more securely. The weight of the wisteria has, over the past few years, pushed the beam down in spite of really sturdy bolts.