Northern Prairie Wildlife Research Center
Found nearly throughout North Dakota, hairy four-o'clock ranges from Wisconsin to Montana south to Louisiana and Texas at elevations below 8,000 ft.
Hairy four-o'-clock is perennial from a heavy, woody taproot below a branching caudex (toughened stem base). Plants are usually about 2 feet tall and covered with short hairs, especially below. The opposite leaves are variable in shape and usually about 2-4 inches long. The rose-pink flowers are often in groups of three, the groups in turn form panicles on the upper half of the plant. Flowers are about 1/2 inch long and open in the evening for pollination by night-flying insects. The 5-angled fruits are about 3/16 inch long and filled with yellow-brown seeds.
Look for hairy four-o'-clock from June to October in native prairie pastures. Cattle seem to avoid these plants, or possibly help spread them, as higher plant numbers are common in pastures where grazing pressure is heavy or moderate. Other members of the genus Mirabilis are used in the tropics and Orient to make medicines, cosmetics, and jelly dyes, but economic uses for hairy four-o'-clock remain 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 name was derived from the Greek nyct, pertaining to "night." The generic name Mirabilis is from the Latin for "wonderful." The genus contains about 40 species that are also sometimes called the "umbrella-worts." The specific name hirsuta means "hairy" in botanical Latin. Hairy four-o'-clock was first described for science under another genus by the eminent German botanist who settled in Philadelphia, Frederick Pursh (1774-1820). He was the first to publish on the many new plants collected by the Lewis and Clark Expedition of 1804-1806.