1. Leaf bases (except sometimes the uppermost) connate around the stem.

E. perfoliatum

1. Leaf bases entirely free and separate from the stem.

2. Leaves with distinct petioles; florets 8–50 (or more) per head.

E. serotinum

2. Leaves sessile or nearly so (at most tapering to a narrow, winged base); florets fewer than 8 (usually 5) per head.

3. Stem densely puberulent on middle internodes; leaves tapered to narrow base (or short-winged petiole), with 3 prominent longitudinal veins (at least on basal half).

E. altissimum

3. Stem glabrous on middle internodes (or sparsely puberulent); leaves truncate to broadly rounded at the base, with only 1 long vein (the midrib) prominent beneath.

E. sessilifolium

All species found in Eupatorium

Eupatorium altissimumTALL BONESET 
Eupatorium perfoliatumBONESET 
Eupatorium serotinumLATE BONESET 
Eupatorium sessilifoliumUPLAND BONESET 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 23, 2018.