Trichostema

1. Calyx lobes all of ± the same length.

T. brachiatum

1. Calyx lobes or lips of very different length.

T. dichotomum

All species found in Trichostema

Trichostema brachiatumFALSE PENNYROYAL 
Trichostema dichotomumBASTARD-PENNYROYAL 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 18, 2017. http://www.michiganflora.net/genus.aspx?id=Trichostema.