1. Flowers in a head, closely enveloped by large scarious-margined bracts; calyx (mostly hidden by bracts) ca. 9-12 mm long.
1. Flowers solitary; calyx ca. 3-5 mm long (not hidden by bracts).
Citation:
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 16, 2025
https://mifloradev.lsa.umich.edu/flora-demo/#/genus/Petrorhagia