Thalictrum rochebrunianum (S)
Hardy in Zones 5-8. Often over winters in zone 3 when sheltered.
Plant crowns 1" below soil surface, at least 2' apart. Prefers rich soil, with lots of organic matter, and partial sun. Best when planted in groups. Blooms in late summer. Stems are very sturdy and do not need to be staked. Plants may require 2-3 seasons to become established.