The Onagraceae, commonly called the willowherb or evening-primrose family, contains around 20 genera and 650 species. This is a widespread family of trees, shrubs and herbs ranging from boreal regions to the tropics. It takes its name from the genus Onagra, which is now Oenothera. The typical pattern in the evening-primroses is to have four sepals and four petals, but in some genera such as Fuchsia the sepals are as brightly colored as the petals and thus gives the impression of having eight petals. One genus, Ludwigia, is 5-merous, while Circaea is 2-merous. This family is especially well represented in western North America, and includes many very showy wildflowers. The name evening-primrose refers to the time of day when the flowers are open, but this applies mainly to Oenothera which is pollinated by night moths. Most other members are open during the day.