Hedeoma

Our two species are both annuals, of weedy habit. Clinopodium acinos and C. vulgare resemble Hedeoma, but these (even if corollas and stamen number are not obvious) can be easily distinguished by the nature of the pubescence on the calyx lobes.

1. Leaf blades linear, sessile, entire; cilia present on all calyx lobes.

H. hispida

1. Leaf blades ± elliptic, short-petioled, often weakly and irregularly toothed; cilia present on only the lower 2 calyx lobes.

H. pulegioides

All species found in Hedeoma

Hedeoma hispidaROUGH PENNYROYAL 
Hedeoma pulegioidesAMERICAN PENNYROYAL 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 17, 2017. http://michiganflora.net/genus.aspx?id=Hedeoma.