It is sort-of like Butterfly Bush, but in the northeast it lives mostly as a large perennial which often needs to re-emerge from the roots after a chilly winter, growing to 3'. Further south, it can become a large shrub/small tree.
It seems to be a very popular border plant on Cape Cod. It is a Mediterranean plant. I like it, and so do bees and butterflies.
Vitex agnus-castus