Publication: Cornell Univ. Agric. Exp. Sta. Mem. 291: 9. 1949.
selected vouchers: WTU
Notes: The taxonomy is disputed, minor differences in spur shape separate European plants (ssp. vulgaris) from North American plants (ssp. macrorhiza), see JPM, Crow & Hellquist (2000) and Taylor (1989) for opposing points of view.