1. Stems with trifid spines ca. 1 cm or more long at the nodes; leaf blades tapering to a short petiole.

X. spinosum

1. Stems spineless; leaf blades ± cordate, mostly about 1–2 times as long as their petioles.

X. strumarium

All species found in Xanthium

Xanthium spinosumSPINY COCKLEBUR 
Xanthium strumariumCOMMON COCKLEBUR 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. September 19, 2017. http://michiganflora.net/genus.aspx?id=Xanthium.