The name of Mirabilis jalapa was given by Carl Von Linneus in 1753 is formed from the scientific Latin Mirabilis meaning "admirable" by allusion to the remarkable colors of its flowers and the specific name jalapa that would refer to its origin in the Jalapa in Guatemala.
Mirabilis jalapa, or Marvel of Peru, is a herbaceous perennial from the Nyctaginaceae family, native to the dry tropical regions of Central and South America, including Guatemala, Mexico, Chile and Peru.
It develops a large, blackish tuberous root with a long history of traditional medicinal use in various parts of the world.
The Four O'Clock Flower grows to 80 cm in height, sometimes more, spreading 40 to 60 cm across.
In temperate climates it disappears in winter and flowers from June to October; in tropical regions it is truly perennial and flowers all year round.
As with the wild species, the flowers open in the evening and close the following day when the sun reaches them, releasing a sweet scent from dusk until deep into the night.
The black fruit appears at the base of the flower once it has fallen. The dichotomous stems are solid, four-angled, fleshy, green to reddish in colour and swollen at the nodes, bearing opposite, oval leaves with a rounded to slightly heart-shaped base, in mid glossy green — paler on chalky soils and in full sun.
Usually, the flowers are yellow, pink and white, but a different combination of flowers growing on the same single four o’clock plant can be found. Another interesting point is a color-changing phenomenon. For example, in the yellow variety, as the plant matures, it can display flowers that gradually change to a dark pink colour. Similarly, white flowers can change to light violet. Despite their appearance, the flowers are not formed from petals– rather they are a pigmented modification of the calyx. Similarly, the 'calyx' is an involucre of bracts. The flowers are funnel-shaped and pentalobed, they have no cup (replaced by bracteal leaves) but are made of a corolla.
Flower patterns are referred to as sectors (whole sections of flower), flakes (stripes of varying length), and spots.