Warren wrote:

Butterfly bush is not invasive. As the first sentence in the link you provided
states, "An invasive plant has the ability to thrive and spread aggressively
outside its natural range." That means you plant one or two, and eventually you
get dozens spreading from the originally intended spot. Butterfly bushes don't
do that.

Butterfly bush is a very aggressive grower. A single plant can go from not much
more than a stick with a couple of leaves to a bush big enough to hide a small
shack in just a few months. But you won't have a dozen new butterfly bushes.

It's a very aggressive grower, but it's not the least bit invasive.

Wrong on all counts. With many varieties, it definitely spreads,
reseeds, and it certainly considered an invasive pest in many areas.