Northern Prairie Wildlife Research Center
Most records of narrowleaf four-o'clock in North Dakota are for counties west or north of the Missouri River, but specimens have been collected in Barnes and Richland counties. This species natural range is from Minnesota to Montana south to Missouri, Texas, and Mexico, but it is sometimes adventive elsewhere.
Narrowleaf four-o'clock is perennial from a deep woody taproot crowned with a branching structure called a caudex. Plants are up to three feet tall and usually branched above. The opposite leaves are about 3-4 inches long, but only about 1/4 inch wide. Flowers occur in groups of 2-4 on stalks. These flowers have no corolla, the group of petals that normally color flowers. Instead, the 1/2 inch long supporting structure for the corolla (calyx) is colored purplish-red to pink and bears long hairs. At maturity, the calyx swells and ripens into a 5-angled fruit containing yellowish brown achenes (seeds).
Look for narrowleaf four-o'clock till mid-September on sandy or gravelly soils in native prairie pastures that are not overgrazed. Other members of the genus Mirabilis, also sometimes called the "umbrella-worts," are used in the tropics and Orient to make medicines, cosmetics, and jelly dyes, but economic uses for narrowleaf 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," likely because the flowers open in the evening. The genus Mirabilis is from the Latin for "wonderful," and contains about 40 species. The specific epithet linearis pertains to the long narrow leaves. Narrowleaf four-o'clock was first described for science under the genus Allionia in the 1800's by Frederick Pursh. Work published in 1901 by the Austrian botanist Anton Heimerl (1857-1942), a specialist in the Nyctaginaceae, convinced the International Botanical Congress to place the plant in its current taxonomic position.
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