I have a soft spot for this perennial, which has been looking terrific lately. Here is one growing in City Hall Park:
The common name for Physostegia virginiana is obedient plant. They call it this because if I were to nudge one of the individual flowers to the left or right, or up or down, the flower would remain in that position for a moment or two.
Physostegia is native, as you may have guessed from the species name, to North America -- it can grow pretty much everywhere east of the continental divide. That said, in the right conditions it will spread pretty quickly and even become a bit invasive.
Phys- usually means nature or body and -stegia means covering in Greek. I am guessing that this is referring to the fact that the flower petals almost look like pill-shaped enclosures.
Physostegia leafs out very early for a summer-blooming perennial. While it starts to bloom in mid-summer, it is this time of year that the plant really stretches out its legs, so to speak. What I like the most about this species is the great color combination of a cotton-candy pink with a clear spring green.