Perovskia atriplicifolia - Russian Sage
Russian Sage is a large, fluffy perennial with soft spikes of lavender-blue flowers and fragrant gray-green foliage. It isn't a sage, but it fits right in with them. Branching sprays of tiny flowers create a magical lavender haze all summer and bring hummingbirds and butterflies.
Perovskia is hardy in almost all zones from 4 to 9. It's drought tolerant and loves lean soil. Deer ignore it, while hummers will fight over it. This is one of the most useful and beautiful fillers for any perennial garden.
Plant Russian sage where you need something large. Great for the back of a mixed border, it grows 3' to 4' tall, and looks terrific with echinacea, rudbeckia, daylilies. And Salvias.
No fuss required. Cut it back to 10" in spring to keep the plants fluffy, then sit back and enjoy.