Four O'Clock
Mirabilis jalapa
The Four O'Clock (Mirabilis jalapa), also known as the Marvel of Peru, is a strikingly ornamental flowering plant in the family Nyctaginaceae. Renowned for its vividly colored, trumpet-shaped blooms that open in the late afternoon — giving rise to its common name — this species has captivated gardeners and naturalists for centuries.
What makes Mirabilis jalapa truly remarkable is its extraordinary genetic variability: a single plant can bear flowers of multiple colors simultaneously, and offspring frequently display traits different from the parent, a phenomenon that fascinated the pioneering geneticist Carl Correns in his early studies of non-Mendelian inheritance.
• The genus name Mirabilis means 'wonderful' or 'admirable' in Latin
• The specific epithet jalapa likely refers to Xalapa (Jalapa), Mexico, its region of origin
• One of the most widely cultivated ornamental plants in tropical and subtropical gardens worldwide
• Known by many common names including 'Marvel of Peru,' 'Beauty of the Night,' and 'Gul-e-aftab' (Flower of the Afternoon) in South Asia
Taxonomy
• Native range spans from Mexico through Central America to parts of northern South America
• Believed to have been domesticated by pre-Columbian peoples for ornamental and possibly medicinal use
• Introduced to Europe in the late 16th century following Spanish colonization of the Americas
• By the 17th century, it had become a popular garden plant across Europe
• Subsequently spread to tropical and subtropical regions worldwide through colonial trade routes
• Now naturalized across much of Africa, South and Southeast Asia, and parts of Oceania
The genus Mirabilis comprises approximately 60 species, most of which are native to the Americas, with the greatest diversity found in Mexico and the southwestern United States.
Root System:
• Produces a large, fleshy, tuberous taproot that can be over 50 cm long
• Tubers are dark brown to black externally, white internally
• Tubers allow the plant to survive drought and regenerate seasonally in regions with cold winters
Stems:
• Erect to spreading, stout, and many-branched
• Stems are quadrangular to rounded, smooth or slightly pubescent
• Hollow internodes; often flushed with purple or red pigmentation
• Branches arise in opposite pairs at each node
Leaves:
• Arrangement: opposite, decussate
• Shape: ovate to broadly ovate (3–12 cm long, 2–8 cm wide)
• Margin: entire (smooth-edged)
• Color: bright green, sometimes with a slightly glaucous sheen
• Petiole: short (1–3 cm), slightly winged
Flowers:
• Inflorescence: dense, terminal or axillary cymes of 3–7 flowers subtended by involucral bracts
• Shape: funnel-shaped (salverform), 2.5–5 cm long, with a slender tube expanding into a 5-lobed limb
• Color: extraordinarily variable — red, pink, yellow, white, magenta, violet, and orange; frequently striped, sectored, or mottled with two or more colors on a single plant
• Fragrance: sweet and jasmine-like, most intense from late afternoon into the evening
• Blooming period: flowers open between 4:00 PM and 8:00 PM (hence the common name), remain open through the night and into the following morning before wilting
• Pollination: primarily by nocturnal hawkmoths (Sphingidae) and other night-flying insects attracted by scent and pale-colored blooms
• No true petals — the showy part is a pigmented, petaloid calyx (involucre)
Fruit & Seeds:
• Fruit: a hard, dry, indehiscent achene (~8–10 mm), wrinkled and dark brown to black when mature
• Seeds: relatively large, with a hard seed coat; can remain viable in soil for several years
• Self-seeds prolifically in favorable conditions, sometimes becoming weedy
• Prefers full sun to light shade; flowering is most prolific in full sun
• Tolerant of poor, sandy, or rocky soils but performs best in well-drained, moderately fertile loam
• Drought-tolerant once established, thanks to its tuberous root system
• Commonly found along roadsides, field margins, waste ground, and garden edges in tropical and subtropical regions
• Attracts a variety of pollinators, particularly nocturnal moths and butterflies
• Serves as a nectar source for hummingbirds in parts of its native range
• Can naturalize aggressively in warm climates, occasionally becoming invasive outside its native range
• Grows at elevations from sea level to approximately 1,500 m in its native habitat
• The root and seeds contain triterpenoid compounds and potentially toxic alkaloids
• Ingestion of seeds or root material can cause gastrointestinal distress, including nausea, vomiting, and diarrhea
• The plant has been used in traditional medicine, but improper dosing can lead to adverse effects
• Handling the plant is generally safe, though individuals with sensitive skin may experience mild dermatitis
• Keep seeds and tubers away from children and pets
Light:
• Full sun (minimum 6 hours direct sunlight) for best flowering
• Tolerates partial shade but with reduced bloom production
Soil:
• Adaptable to a wide range of soil types — sandy, loamy, or clay
• Prefers well-drained soil with moderate fertility
• Tolerates slightly acidic to slightly alkaline pH (6.0–7.5)
• Avoid waterlogged or heavily compacted soils
Watering:
• Water regularly during establishment; once established, the plant is notably drought-tolerant
• Avoid overwatering, which can lead to tuber rot
• In containers, allow the top 2–3 cm of soil to dry between waterings
Temperature:
• Thrives in warm conditions; optimal growth at 20–30°C
• Frost-sensitive — tops die back with the first frost
• In temperate zones, tubers can be dug up in autumn, stored in cool dry conditions (7–10°C), and replanted after the last frost
Propagation:
• Seeds: sow directly outdoors after last danger of frost, or start indoors 4–6 weeks early; seeds benefit from overnight soaking in warm water to improve germination
• Tuber division: separate and replant tubers in spring
• Germination typically occurs within 7–14 days at 20–25°C
Common Problems:
• Aphids may colonize new growth; treat with insecticidal soap or neem oil
• Rust (fungal disease) can occur in humid conditions; ensure good air circulation
• Poor flowering usually indicates insufficient sunlight
• In warm climates, self-seeding can lead to weedy spread — deadhead spent flowers to control
Ornamental:
• Widely planted in borders, cottage gardens, containers, and as hedging in tropical landscapes
• Valued for its long blooming season (summer through autumn), vibrant colors, and evening fragrance
• Popular in moon gardens designed for evening enjoyment
Traditional Medicine:
• Used in folk medicine across Latin America, India, and parts of Africa
• Root preparations have been used as purgatives and diuretics
• Leaf poultices applied topically for wounds and inflammation in some traditional systems
• Flower extracts used in certain Ayurvedic preparations
Scientific Research:
• Carl Correns used Mirabilis jalapa in landmark experiments (1900–1909) demonstrating cytoplasmic (non-Mendelian) inheritance through variegated leaf color
• This work was foundational in the discovery of extranuclear (plastid) inheritance
• Plant continues to be used in genetics education to demonstrate incomplete dominance and variegation
Other Uses:
• Flower pigments have been used as a natural food coloring and as a pH indicator in chemistry (the pigment changes color in acidic vs. basic solutions)
• In some regions, flower extracts are used to dye fabrics
Fun Fact
The Four O'Clock played a pivotal role in the history of genetics. In the early 1900s, German botanist Carl Correns used Mirabilis jalapa to demonstrate that certain traits are inherited through the cytoplasm of the egg cell rather than through nuclear genes — a phenomenon called maternal (cytoplasmic) inheritance. His experiments with variegated (green-and-white) leaf patterns showed that offspring leaf color depended solely on the mother plant's phenotype, regardless of the pollen source. This was one of the first documented cases of non-Mendelian inheritance and helped lay the groundwork for the field of extranuclear genetics. Additional fascinating facts: • A single Four O'Clock plant can simultaneously produce flowers of completely different colors — red, yellow, pink, white, and striped — due to transposon (jumping gene) activity that causes somatic mutations in flower color genes during development • The flowers open in the late afternoon to coincide with the activity patterns of their primary pollinators, hawkmoths, and close by mid-morning the next day — each individual flower lasts only about 16–20 hours • The plant's pigments (betalains) are the same class of compounds found in beets and cacti, and they can be extracted and used as a natural pH indicator, turning red in acids and yellow in bases • In Victorian England, Four O'Clocks were a staple of cottage gardens and were sometimes called 'the poor man's bouquet' because of their prolific, colorful, and fragrant blooms requiring minimal care • The tuberous roots can grow remarkably large — specimens weighing over 10 kg have been recorded in tropical gardens
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