Triadenum

1. Sepals 2.5–4.3 (–5) mm long, usually blunt or rounded; styles 0.5–1 (–1.5) mm long.

T. fraseri

1. Sepals 5–7 mm long, acute; styles becoming 1.7–3 mm long (best seen in fruit).

T. virginicum

All species found in Triadenum

Triadenum fraseriMARSH ST. JOHN'S-WORT 
Triadenum virginicumMARSH ST. JOHN'S-WORT 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 16, 2017. http://www.michiganflora.net/genus.aspx?id=Triadenum.