To my understanding, It is an invasive species in Europe (not the US) where it has escaped the garden and naturalized. It is a native species here. I find it fairly easy to control in my garden . Has it become a garden thug in your garden? or in the neighborhood? It is a welcomed plant because it attracts bees and butterflies. As a plant, it might not fit in your garden because it does need a certain amount of space because it can attain some size and become ungainly. IT does not seed out prolifically here outside of Austin. I would be more concerned of the root stolens than the seedlings. It makes a colony in the wild due to spreading stolens.

Are we talking about Soldago candensis (taller likes deeper wetter soils), S. nemerosa ( smaller but spreads easier in dry alkaline soils.