Skip to main content


four-o'clock, common name for members of the Nyctaginaceae, a family of plants found in warm climates, especially in the Americas, chiefly as herbs but often in the tropics as shrubs or trees. Species native to the United States are mostly restricted to the southern and Pacific regions, e.g., the sand verbena of the deserts. The four-o'clock, or marvel of Peru (genus Mirabilis), of tropical Asia and America and the woody bougainvillea vine with its showy bracts are widely cultivated as garden ornamentals in suitable climates and in greenhouses. Some members of the family are of minor importance medicinally. Four-o'clocks are classified in the division Magnoliophyta, class Magnoliopsida, order Caryophyllales, family Nyctaginaceae.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"four-o'clock." The Columbia Encyclopedia, 6th ed.. . 22 Jul. 2019 <>.

"four-o'clock." The Columbia Encyclopedia, 6th ed.. . (July 22, 2019).

"four-o'clock." The Columbia Encyclopedia, 6th ed.. . Retrieved July 22, 2019 from

Learn more about citation styles

Citation styles gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

The Chicago Manual of Style

American Psychological Association

  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.