1. Terminal inflorescence densely crowded, compact, the long bracts with prolonged spine-tipped teeth; calyx mostly 10 mm or more long.
D. parviflorum
1. Terminal inflorescence elongate after flowering, the small bracts scarcely if at all exceeding the pedicels, entire, spineless; calyx ca. 6–8 mm long.
D. thymiflorum
All species found in Dracocephalum
Citation:
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. January 25, 2021. https://michiganflora.net/genus.aspx?id=Dracocephalum.