Dracocephalum

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

Dracocephalum parviflorumDRAGONHEAD 
Dracocephalum thymiflorumTHYME-LEAVED DRAGONHEAD 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. July 26, 2017. http://michiganflora.net/genus.aspx?id=Dracocephalum.