Plants in the mainly tropical and subtropical Four o'clock Family (Nyctaginaceae) are annual and perennial herbs, shrubs, and trees with opposite (rarely alternate), simple, smooth-edged or wavy-edged leaves, petalless flowers with a flaring, tubular, petallike, 4 or 5-lobed calyx and a superior ovary, and fruit in the form of an achene, nut, or winged samara.

Listed below are some of the southeastern Arizona plants in this family.