Later I noticed that this one plant in particular looked very different from what it was "supposed to be." They were all seedlings when I adopted them and as seedlings looked vaguely similar but as they grew the leaves changed. Then the salvias began blooming while the other plant was still all foliage. A couple weeks later the buds began to form in small clusters of little fuzzy ball shaped buds. Immediately I had a suspicion as to what its identity was but needed it to bloom to be sure. Here's how it appears today:
A hardy ageratum or blue mist flower (Eupatorium coelestinum). This is just now starting to bloom but should last well into the fall. It should return next year (zones 5-9) and could reseed.
It's always nice to have more blue in the garden!