As the summer sun begins its descent and the afternoon heat mellows into a gentle evening breeze, something magical happens in gardens across Japan. Around 4 o’clock in the afternoon, vibrant trumpet-shaped flowers begin to unfurl, filling the twilight air with their sweet fragrance. These are oshiroibana, known in English as four o’clock flowers, a beloved summer bloomer that has captured hearts in Japan since the Edo period.
What makes these flowers truly special is their unique blooming pattern. Unlike most flowers that greet the morning sun, four o’clock flowers prefer the company of evening shadows, opening their petals as day transitions to night and closing again by the following morning. This enchanting behavior, combined with their ability to display multiple colors on a single plant, has made them a fascinating subject for both gardeners and curious children throughout Japan.
What is Oshiroibana (Four O’Clock Flower)?
The four o’clock flower, scientifically known as Mirabilis jalapa, belongs to the Nyctaginaceae family. Native to tropical regions of Central and South America, particularly Mexico and Peru, this perennial plant has naturalized extensively throughout Japan since its introduction during the early Edo period.
In its natural habitat, the plant can grow quite substantial, reaching heights of up to 100 centimeters with a bushy, spreading form. The leaves are deep green, oval-shaped, and arranged in opposite pairs along the stems. What appears to be the flower’s colorful petals are actually modified sepals called the calyx, while the true sepals are actually a structure called bracts at the base of the flower.
The flowers themselves are trumpet-shaped with a distinctive long tube, measuring about 2 to 3 centimeters in diameter when fully open. They bloom continuously from June through October, producing an abundance of flowers throughout the summer and early autumn months.
The Origin of the Name “Oshiroibana”
The Japanese name “oshiroibana” literally translates to “white powder flower,” and this name has a charming origin story rooted in Edo period Japan. When the black seeds of the plant are cracked open, they reveal a white, powdery substance that resembles traditional Japanese face powder called “oshiroi.”
During the Edo period, this powdery endosperm was actually used as a substitute for cosmetic powder. Children in Japan have traditionally enjoyed playing with these seeds, pretending the white powder is makeup. This endearing connection between the plant and childhood memories has helped maintain its popularity across generations.
The alternative Japanese name “yugesho” (evening makeup) beautifully captures another aspect of the flower’s character. The name evokes the image of a woman applying makeup before going out for the evening, perfectly paralleling the flower’s habit of opening its blooms as twilight approaches.
Unique Characteristics of Four O’Clock Flowers
Blooming at Twilight
The most distinctive feature of four o’clock flowers is their unusual blooming schedule. True to their English name, these flowers typically begin opening around 4 o’clock in the afternoon, continuing to bloom through the evening and night hours. By the following morning, usually around 10 AM, the flowers close and wither.
This nocturnal blooming pattern is an evolutionary adaptation. The flowers’ long tubular structure requires pollinators with equally long proboscises to reach the nectar. In Japan, hawk moths (suzumega) are the primary pollinators, using their long tongues to access the nectar while transferring pollen from flower to flower during their nighttime feeding.
The timing isn’t always precise at 4 PM. Cloudy weather or cooler temperatures can cause the flowers to open earlier in the day, while particularly hot conditions might delay their opening until later in the evening.
Multi-Colored Flowers on One Plant
One of the most remarkable characteristics of oshiroibana is its ability to produce flowers of different colors on the same plant. A single four o’clock plant might display red, pink, white, and yellow flowers simultaneously, along with bi-colored or striped varieties.
This phenomenon occurs naturally and isn’t the result of grafting or genetic modification. The scientific name Mirabilis, which means “wonderful” or “marvelous” in Latin, was chosen specifically to reflect this amazing color variation. Some flowers even change color as they age, with yellow varieties gradually shifting to deep pink, or white flowers developing violet tones.
This multi-colored display creates a vibrant, eye-catching garden feature that continually surprises observers. The unpredictable nature of which colors will appear makes each plant unique.
Sweet Evening Fragrance
As twilight deepens and the flowers fully open, they release a sweet, pleasant fragrance into the evening air. This scent isn’t overpowering like some heavily perfumed flowers, but rather a gentle, refreshing aroma that becomes more noticeable as night falls.
The fragrance serves an important purpose beyond delighting human noses. Like the flower’s timing and shape, the scent helps attract nocturnal pollinators. The combination of visual appeal (especially the white and yellow varieties that glow in dim light), sweet nectar, and alluring fragrance creates an irresistible invitation for hawk moths and other evening insects.
Cultural Significance in Japan
Four o’clock flowers hold a special place in Japanese culture, particularly in childhood memories. For generations of Japanese children, these flowers have been companions in play. The tradition of making “parachutes” from the flowers by gently separating the pistil from the sepal, or cracking open the black seeds to reveal the white powder inside, connects past and present.
The flowers carry the language of flowers (hanakotoba) meanings of “timidity,” “shyness,” and “doubtful love.” These associations likely stem from the flower’s habit of blooming away from the bright spotlight of day, as if too shy to show itself during peak hours. The multiple colors on one plant also inspired the meaning of “doubtful love,” perhaps suggesting an uncertain or changeable heart.
Despite these somewhat melancholic flower language meanings, oshiroibana is cherished for its reliable summer presence and the nostalgic memories it evokes. The flowers have become so naturalized in Japan that they’re considered part of the everyday landscape, growing wild along roadsides, in empty lots, and between cracks in concrete.
Growing Four O’Clock Flowers: A Complete Guide
Best Growing Conditions
Four o’clock flowers are remarkably hardy and adaptable, which explains their successful naturalization throughout Japan. They thrive in full sun locations but can also tolerate partial shade, though flowering may be less prolific and colors less vibrant in shadier spots.
The plants prefer well-drained soil but aren’t particularly fussy about soil quality. They can grow in poor soil conditions and even establish themselves in challenging environments like sidewalk cracks. This resilience makes them an excellent choice for beginning gardeners or those seeking low-maintenance plants.
| Growing Factor | Requirement | Notes |
|---|---|---|
| Sunlight | Full sun to partial shade | Best flowering in full sun |
| Soil Type | Well-drained, any quality | Tolerates poor soil |
| Water Needs | Low to moderate | Drought-tolerant when established |
| Temperature | Warm climate preferred | Perennial in mild areas, annual in cold regions |
Temperature-wise, four o’clock flowers are tropical by origin but have adapted well to temperate climates. In warmer regions of Japan (generally from Kanto southward), the tuberous roots can survive winter underground, allowing the plant to return as a perennial. In colder regions, they’re typically grown as annuals, though the abundant seeds ensure new plants the following year.
Planting and Care Tips
Starting four o’clock flowers from seed is straightforward. Seeds should be sown in spring, from April through June, when soil temperatures consistently reach above 20°C. The large, black seeds can be direct-sown into garden beds or started in pots.
When planting, space plants 30 to 45 centimeters apart to allow for their spreading growth habit. Four o’clock flowers have a taproot system, meaning they develop one main root that grows straight down. This makes them somewhat resistant to transplanting, so it’s best to plant seeds directly in their final location or handle transplants very carefully to avoid damaging the root.
For watering, established plants are quite drought-tolerant. In garden beds, they typically don’t need supplemental watering except during extended dry periods. Container plants should be watered when the soil surface feels dry.
Four o’clock flowers require minimal fertilization. In fact, overly rich soil can result in lush foliage at the expense of flowers. A light application of balanced fertilizer once or twice during the growing season is sufficient.
Propagation Methods
The easiest propagation method is through seeds. Each flower produces one large, round black seed that matures quickly after the flower fades. These seeds are highly viable and can be collected in late summer and autumn for planting the following spring.
Seeds can be stored in a cool, dry place over winter. They also self-sow readily, often producing volunteer plants the following year without any human intervention. This self-seeding tendency has contributed to the plant’s widespread naturalization in Japan.
In warmer climates where the plants survive winter as perennials, the tuberous roots can be divided in spring. However, due to the taproot nature of the plant and the ease of seed propagation, division is rarely necessary or practiced.
Where to See Oshiroibana in Japan
Unlike some flowers that have specific famous viewing spots, four o’clock flowers are delightfully democratic in their distribution. They can be found throughout Japan, from Hokkaido to Kyushu, making them accessible to everyone.
The best places to observe these evening bloomers include:
Urban gardens and residential areas: Many Japanese homes feature oshiroibana in their gardens, particularly in older neighborhoods where traditional plantings are maintained.
Roadsides and vacant lots: The plant’s hardy nature allows it to thrive in less-maintained spaces. Walking through residential areas in the early evening during summer often reveals clusters of colorful four o’clock flowers.
Parks and public spaces: While not typically featured as showcase flowers, oshiroibana often grows along park borders or in naturalized areas.
Temple and shrine grounds: Some traditional religious sites include these flowers in their gardens, where they contribute to the peaceful evening atmosphere.
The beauty of oshiroibana is that you don’t need to plan a special trip to famous gardens. Simply taking an evening walk during summer in almost any Japanese neighborhood will likely reward you with the sight and scent of these charming flowers as they begin their nightly display.
For the best viewing experience, plan your observation for the magic hour between 4 PM and dusk. This is when you’ll see the flowers at their most active, gradually opening their colorful trumpets to greet the evening. The experience is particularly special on warm summer evenings when the air is still and the sweet fragrance lingers.
Summary
Four o’clock flowers (oshiroibana) represent a perfect blend of natural wonder and cultural nostalgia in Japan. Their unique habit of blooming at twilight, combined with their ability to display multiple colors on a single plant and their sweet evening fragrance, makes them truly special members of Japan’s summer flora.
From their introduction during the Edo period to their current status as beloved naturalized plants found throughout the country, these flowers have woven themselves into the fabric of Japanese life. They remind us that beauty doesn’t always need to be grand or rare—sometimes the most enchanting experiences are found in everyday moments, like watching flowers open as the day transitions to evening.
Important safety note: While four o’clock flowers are beautiful and largely harmless to observe and touch, the seeds and roots contain a toxic compound called trigonelline. These parts should never be ingested, as they can cause nausea, abdominal pain, and diarrhea. Keep children and pets from eating any part of the plant, and wash hands after handling seeds during planting.
Whether you’re a gardener looking for an easy-to-grow, low-maintenance plant with unique characteristics, or a flower enthusiast curious about Japan’s naturalized flora, oshiroibana offers something special. Next time you’re in Japan during summer, make a point to take an evening walk and watch for these charming flowers as they perform their daily ritual of welcoming the night. You’ll understand why generations of Japanese people have treasured these enchanting evening bloomers.
