Since yellow is the most common color for stamens and stigmas, it makes sense that those flowers that have a yellow perianth (including the "throat") tend to be monochromatic, including Ozark Sundrops. Other examples include flowers from certain members of St. Johnswort (Hypericum), Daffodils (Narcissus), and Prickly Pear Cactus (Opuntia). This species was formerly known as Oenothera macrocarpa.