Four o’ Clock
Mirabilis jalapa
NEMBA category
English: Four o’ Clock, Four o’ Clock Flower, Heart-leaf Four-o’ Clock, Heart-leaf Umbrella-wort, Snotweed, Umbrella-wort, Marvel of Peru, Beauty of the Night, False Jalap, Wonder Flower
Afrikaans: Vieruurtjie, Vieruurblom
Four o’clock (Mirabilis jalapa) is a bushy, tender perennial that grows tall on erect, branching stems. A classic garden favourite, it is known for its fragrant, funnel-shaped, tubular flowers with five flaring petal-like lobes, which bloom in a variety of colours from early to mid-summer through autumn.
True to its name, the flowers open in the late afternoon (around four o’clock) and remain open only until the following morning, adding a unique charm to gardens.
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Origin:
Native to the tropical Americas, most likely Peru.
Distinguishing features:
Evening opening flowers: Trumpet-shaped, fragrant flowers that typically open in the late afternoon (around 4 pm) and remain open through the night, closing by morning.
Multi-coloured flowers: Flowers can be single-coloured (e.g., yellow, red, white) or variegated with splashes of different colours, often with multiple colours appearing on the same plant.
Black, wrinkled seeds/fruits: Produces distinctive, small, black, wrinkled, spherical fruits that look like tiny peppercorns, containing the actual seed.
Fleshy tuberous roots: Develops a large, fleshy root that allows it to survive dry periods and regrow.
Overall appearance:
A bushy, herbaceous perennial plant that typically grows as an annual in cooler climates but persists from its tuberous root in warmer regions. It has a rounded, spreading habit with stout, branched stems.
Height:
Typically grows to between 0.6 and 1 metre tall.
Width:
Can spread 0.5 to 1 metre wide.
Leaves:
Simple, arranged in opposite pairs along the stems. They are oval to triangular-ovate, with pointed tips and smooth, entire margins. The leaves are typically dark green, smooth (glabrous), and measure about 4 to 15 centimetres long.
Flowers:
Trumpet-shaped, fragrant, and about 3 to 5 centimetres long and 2 to 3 centimetres wide at the mouth. They appear in clusters at the tips of the stems and in leaf axils. They come in a wide range of colours including red, pink, yellow, white, or magenta. Often, a single plant will produce flowers of different colours, or even variegated flowers with stripes or splashes of multiple colours. The flowers typically open in the late afternoon (around 4 pm, hence the common name) and remain open throughout the night, closing by morning. The plant is hermaphroditic, with both male and female parts in each flower.
Flowering season:
In South Africa, it primarily flowers during summer and autumn (around November to April), but its long flowering period can extend well into warmer parts of the year, especially in regions like the Eastern Cape.
Fruits:
The actual fruit is an achene, which is a small, hard, black, wrinkled, egg-shaped structure, about 8 millimetres long, resembling a miniature hand grenade or peppercorn. These are often mistakenly referred to as the "seeds." Each of these "fruits" contains a single true seed.
Seeds:
Small, light brown to blackish, enclosed within the hard, wrinkled, black fruit. The seeds are viable for several years and contribute to the plant's spread. They are primarily dispersed by birds or other animals that eat the fruits, or by human activity (e.g., discarded garden waste).
Bark:
The stems are stout, branched, succulent (fleshy) when young, and can become slightly woody at the base as the plant matures. They are typically green, sometimes tinged with purple, and often swollen at the nodes. It does not develop true bark.
Thorns:
This species does not have thorns.
Wood:
The stems are primarily herbaceous and fleshy, becoming slightly woody at the base in older plants.
Roots:
Develops a large, fleshy, tuberous taproot. This root acts as a storage organ, allowing the plant to survive adverse conditions like drought or cold (by dying back to the ground) and resprout vigorously in favourable conditions.
Soil type:
Highly adaptable and can grow in a wide range of well-drained soils, from sandy to loamy. It prefers fertile soils but is quite tolerant of poorer conditions and can withstand drought once established.
Aspect:
Prefers full sun for the best flowering and growth. It can tolerate partial shade, but flower production may be reduced.
Ediblity:
NOT EDIBLE. All parts of the plant, especially the roots and seeds, are toxic if ingested.
Toxicity:
All parts of Mirabilis jalapa, particularly the roots and seeds, are toxic to humans and animals if ingested. They contain various alkaloids and other compounds that can cause severe gastrointestinal upset, including nausea, vomiting, diarrhoea, and abdominal pain. Skin contact with the sap can also cause mild dermatitis or irritation in sensitive individuals.
Uses:
Widely cultivated globally as an ornamental garden plant for its attractive, fragrant, and uniquely timed flowers. It is a popular choice for night gardens or patios where its evening fragrance can be enjoyed. Historically, some traditional medicinal uses were attributed to it in various cultures (often external or highly specific preparations, despite its toxicity), and its flowers were sometimes used as a natural food dye (though this is risky due to toxicity). The distinctively marked seeds have also been used in some crafts.
Ecology:
As an alien species in South Africa, Mirabilis jalapa readily escapes cultivation, particularly from discarded garden waste. It forms dense clumps in disturbed areas, roadsides, waste ground, and old gardens, where it can outcompete native vegetation and reduce biodiversity. Its prolific production of viable seeds (which are dispersed by birds and human activity) and its persistent tuberous root system enable it to spread rapidly and become established. Its flowers are primarily pollinated by night-flying insects, such as moths, due to their opening times and fragrance.
Distribution and habitat:
Widely cultivated in gardens across all provinces of South Africa. It has become extensively naturalised and is considered an environmental weed throughout the country, particularly in warmer regions with sufficient moisture. It is very common in the Eastern Cape (frequently observed in disturbed areas, roadsides, and old garden sites around Kenton-on-Sea), KwaZulu-Natal, Mpumalanga, Limpopo, Gauteng, and Western Cape. It invades disturbed sites, urban open spaces, waste ground, and neglected agricultural land.
Derivation of name:
The genus name Mirabilis is Latin for "wonderful" or "marvellous," referring to the striking beauty and unique flowering behaviour (opening in the evening) of its flowers.
The species epithet jalapa refers to Jalapa (or Xalapa), a city in Mexico, although the plant's true origin is believed to be in Peru.
The common name "Four O'Clock Flower" directly refers to the typical time of day its flowers open.
Historical aspects:
Mirabilis jalapa was one of the earliest plants to be widely introduced to Europe from the Americas, becoming a popular ornamental in the 16th century. Its unique habit of opening its fragrant flowers in the late afternoon and closing them by morning captivated botanists and gardeners. It also played a significant role in early genetics research, as Carl Correns used it to demonstrate the concept of incomplete dominance in plant inheritance, where different flower colours could mix to form new colours. Its hardiness and prolific seed production led to its widespread naturalisation in many parts of the world, including South Africa.
NEMBA status:
Not explicitly listed as a declared invasive species (Category 1a, 1b, or 2) under NEMBA. However, as a non-indigenous species that readily naturalises and can form dense stands, it is often considered an environmental weed that requires management where it escapes into natural areas. It may be treated as a Category 3 species in certain contexts (e.g., restrictions on planting or sale if it poses a significant risk to an ecosystem). It is always advisable to check the most current local environmental regulations.
Interesting facts:
This plant is like a natural clock! Its beautiful, fragrant flowers typically open up around "four o'clock" in the afternoon, putting on a show for the evening.
You can sometimes find a single plant producing flowers of completely different colours—like bright pink next to sunny yellow, or even striped petals—all at the same time! It's like a living rainbow.
While its flowers are lovely, its seeds look like tiny, black, wrinkled hand grenades or peppercorns, and they're quite toxic, so don't be tempted to eat them!
This plant was famously used by an early geneticist, Carl Correns, to discover how some traits mix and blend, rather than following simple "dominant" or "recessive" rules. It helped unlock secrets of plant inheritance!
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