An easily recognized genus, with jointed or segmented and branching stems, usually strongly flattened. The flowers are showy and, in our species, yellow or yellow with a red center. The plants are practically indestructible and if uprooted will survive many days of desiccation in hot sun before transplantation and recovery.
1. Segments of stem scarcely if at all flattened, readily detaching, less than 3 cm long (excluding spines); areoles mostly with 3 or more well-developed spines.
1. Segments of stem strongly flattened, not detaching, usually more than 5 cm long; areoles mostly with 0–1 well-developed spines.
All species found in Opuntia
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. July 25, 2017. http://michiganflora.net/genus.aspx?id=Opuntia.