A western species, L. redowskii (Hornem.) Greene, has frequently been reported to range into Michigan as a waif, but all specimens so labeled are better referred to L. squarrosa (with even immature fruit showing 2 rows of marginal prickles). Each nutlet of L. redowskii has only a single row of marginal prickles and hence appears distinctly less prickly than in our species, which also tends to have larger nutlets and stems with more appressed pubescence.
All species found in Lappula
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. April 29, 2017. http://michiganflora.net/genus.aspx?id=Lappula.