Salvia nemorosa, anyone?
Specifically, Blue Hill, Blue Queen, Caradonna, and East Friesland. Including flower spikes, how tall does it get in your garden? Bluestone Perennials says up to 24" but whenever I see a picture of it growing in someone's garden, it always looks way taller than that. My 1 gallon East Friesland didn't quite make it to 24" last year, but that was its first year so I'm expecting it to do better this year. (I know it can differ by zone/conditions -- I'm in zone 6/MA -- but I'll take whatever info I can get.)