Northern Prairie Wildlife Research Center
In the evening, the showy wild four-o'clock opens its flowers to the insects that nightly roam the Dakota prairies. Found nearly throughout our state, the plant originally lived in the grasslands that stretch from Saskatchewan to Texas, but has since spread as a weed eastward to the Atlantic States.
Wild four-o'clock is a hairless perennial 2-3 feet tall. Roots are thick and black. Pairs of heart-shaped leaves are widely separated along the thin stems. About a dozen pink, funnel-shaped flowers form open clusters at the top of the plant. The part that gives color to the flowers of most plants (the corolla) is oddly absent in the four-o'clocks. Instead, it is the normally green flower cup (the calyx) that is colored. The 5-ribbed fruits are about 3/16 inch long.
The plant seems to thrive under grazing in our area, perhaps because of its ability to colonize sites where soils are disturbed, as by trampling or burrowing animals. Other members of the genus Mirabilis are used in the tropics and Orient to make medicines, cosmetics, and jelly dyes, but knowledge of any economic uses for our wild four-o'clock has been lost or remains to be discovered.
This species is a member of the four-o'clock family (Nyctaginaceae) which has about 300 species found mostly in the American tropics. The family and species names are from the Greek nyct, pertaining to "night." Mirabilis is from the Latin for "wonderful." Wild four-o'clock was discovered by the eminent French botanist Andre Michaux (1746-1802). In 1792, Michaux was unsuccessfully nominated by Thomas Jefferson to accompany Meriwether Lewis on a proposed expedition to explore the wilderness that lay west of the Mississippi River.