When this flower blooms, you'd better head home for dinner, or your mom will scold you.

Four o'clock floweris truly a plant that feels deeply familiar. As the most widely grown home garden herbaceous flower among Chinese folk, even if you don't know its name, you may have seen it since childhood. However, like common flowers such as sunflowers, scarlet sage, and morning glories, the four o'clock flower is not a native plant, but comes from distant Latin America.

The four o'clock flower is also a flower I have grown since childhood. Back then I didn't know its proper name, only that adults called itpink bean flowerorlandmine flower. It wasn't until many years later when I saw it in a high school biology textbook that I suddenly realized it was an old friend I had known all along.

Four o'clock flower, could it also be your old friend? Image: Khalid Mahmood / wikimedia

So many names

The four o'clock flower belongs to the Nyctaginaceae family, and is a sister in the same family as the bougainvillea commonly seen in South China. Its genus Mirabilis includes about 50 species,with tropical South America as the center of distribution. As the most common species in this genus, the four o'clock flower was cultivated and used as a medicinal plant by indigenous peoples long ago.

The first botanist to describe the four o'clock flower was Carl Linnaeus, who in 1753 gave it the scientific name Mirabilis jalapa, formally publishing it in Species Plantarum. Linnaeus noted in the text that the four o'clock flower's colors show many unusual variations, and therefore gave it the genus name Mirabilis, meaning"wonderful"。

Even on the same plant, the four o'clock flower's diverse colors can be seen. Image: Vaikoovery / wikimedia

As for the explanation of the specific epithet jalapa, there are currently two theories. One theory refers to the four o'clock flower'splace of origin, possibly from the Jalapa region of Guatemala.

Another explanation may be related to the city of Xalapa in Mexico, which once produced apurgativecalled jalap, so this place name can also be written as Jalapa. This purgative was extracted from the tubers of a Convolvulaceae plant, Ipomoea purga (tentatively given the Chinese name "purgative sweet potato," English name tuberous jalap), and this plant'sflowers happen to be quite similar to those of the four o'clock flower. When naming new plants, botanists often refer to the names of known similar plants, so this explanation also seems quite reasonable.

The beautiful Ipomoea purga can actually be used as a purgative. Image: Michael Kesl / biolib.cz

After the four o'clock flower was introduced to China, it was widely planted across the country, and people everywhere gave itall kinds of folk names, such as dinner flower, bath flower, night darling, wild jasmine, wild lilac, nail flower, rouge flower, landmine flower, pink bean flower, and so on, each one more down-to-earth than the last.

In fact, these folk names precisely reflect the habits of the four o'clock flower: for example, it is a flower that only blooms in the evening, mainlyblooming at night; the flowers are fragrant,with a scent similar to jasmine; the petals can be crushed and used todye nails or make rouge, and so on.

The four o'clock flower also has two commonly used English folk names -- the marvel of Peru and four o'clock flower. The first name is remarkably similar in spirit to the scientific name given by Linnaeus, while the latter coincides with the Chinese folk name. Seeing this flower bloom means it will soon be dark,which is when your mom calls you home for dinner or a bath。

It's 2:45?! Image: Salvatore Ingala / wikimedia

A girl's earring, and a boy's landmine

In temperate regions, the four o'clock flower is usuallya herb no taller than 1 m, withering and dying each winter, then growing a new generation the following year.

In fact, the four o'clock flower, native to tropical America, is originally aperennial plantthat can grow for many years, with thick underground rhizomes that can store nutrients; the above-ground part can also grow to 1 to 2 m tall, with dense branching and vigorous growth, looking rather like a small shrub.

The tuberous roots of the four o'clock flower are dried by unscrupulous vendors to pass off as Gastrodia elata or ginseng, but they contain toxins such as trigonelline, and eating them by mistake will cause vomiting and diarrhea. Image: VisionsPictures / mindenpictures

The flowers of the four o'clock flower are also somewhat unusual, looking like a slimmed-down morning glory, but the two still differ. The morning glory's corolla is formed by 5 fused petals, with 5 green sepals wrapping the base, and the corolla and calyx are clearly distinguished; although the four o'clock flower's flower is also similarly deep funnel-shaped, with a 5-lobed green sepal-like structure at the base, that is not a true calyx, but rather aninvolucre。

Calendar Lady's expansion time

The calyx and petals (accurately called the corolla) are collectively known as the perianth, which is a necessary structure for composing a complete flower (which also includes the pedicel, receptacle, androecium, and gynoecium). The involucre is specialized from the leaves near the base of the inflorescence,and is completely different from the calyx in origin。

The brightly colored part of the four o'clock flower has only one layer, making it impossible to distinguish calyx from petals, so we can only call it theperianth, and a flower with this single-layer perianthis not a complete flower, so flowers like the four o'clock flower are also called single-perianth flowers. The many members of the Ranunculaceae previously introduced by Species Calendar are also single-perianth flowers (such as Pulsatilla chinensis, Anemone raddeana, Clematis acerifolia, Asarum sieboldii, etc.).

Morning glory (left) and four o'clock flower (right). Image: Fanghong & KENPEI / wikimedia

The four o'clock flower, which chooses to bloom at night, of course misses insects active during the day, but it has another trick, which is to release a relatively strong floral fragrance toattract night-active moths for pollination。

The four o'clock flower's flower is relativelynarrowand deeply cylindrical, and only hawk moths with long proboscises have the ability to sip its nectar. After the four o'clock flower blooms, both the pistil and stamens extend beyond the perianth tube, making it easy to brush pollen onto visiting hawk moths, or to unload pollen brought by the hawk moth.

The Japanese hawk moth (Theretra japonica) shuttles among four o'clock flowers. Image: Satoshi Kuribayashi / mindenpictures

Those born in the 1980s who grew up in rural areas must have "bullied" four o'clock flowers plenty as children. Girls who loved beauty would pick the flowers, crush them, and dye their nails; or they would pluck off a flower, carefully slide the perianth tube over the pistil's style, so that the swollen stigma just catches at the base of the tube, letting the whole flower hang down through the style, then tuck the spherical ovary at the base into their ear, making amori girl-style earring。

Naughty boys mainly picked its fruits to use as "bullets." In the mature four o'clock flower fruit, the deep black rind becomes hard, and the surface patterns make it look likea miniature landmine. Fired from a homemade slingshot, it would hurt a bit when it hit someone, but not enough to cause injury, so it became a sharp weapon in chase games (bullying classmates).

Have you ever played with this kind of "landmine"? Image: Doctoroftcm / wikimedia

From experimental subject to invasive plant

The story about the four o'clock flower that left the deepest impression on me is the scientific experiment using it as material in a high school biology textbook.

Around 1900, German botanist Carl Correns discovered variant four o'clock flower individuals with albino and variegated leaves, and then carried out hybridization experiments, only to find thatthe leaf color of hybrid offspring depends only on the maternal traits, and has nothing to do with the paternal parent that provides pollen. He guessed that some factor outside the cell nucleus must have influenced the offspring's phenotype, causing the experimental results to not conform to Mendel's law of gene segregation and independent assortment.

Although it has little effect on the leaf traits of offspring, let's still get to know what four o'clock flower pollen looks like under an electron microscope. Image: Albert Lleal / mindenpictures

Later further research confirmed that the gene controlling four o'clock flower leaf color is located in thechloroplastsin the cytoplasm. When sperm and egg combine, only the sperm's cell nucleus fuses with the egg cell, so the chloroplast genes in the egg cell become the decisive factor controlling offspring leaf color. This also became aclassic case of cytoplasmic inheritance。

in botany. Besides this famous leaf color inheritance experiment, the four o'clock flower's color changes are also full of surprises. The four o'clock flower's colors can be described as endlessly varied; besides the common purplish red, white, and yellow, there are alsomosaic colors, striped colors, and splashed colors, and sometimes even the same plant, or even the same branch, may produce flowers of different colors.

Research shows that the inheritance of four o'clock flower color isincomplete dominance; for example, when pure red flowers (AA) are crossed with pure white flowers (aa), they produce pink or mosaic offspring (Aa), rather than pure red. In this case,the red and white genes have equal strength, and neither can completely dominate the other.

Four o'clock flowers with different colors. Image: KENPEI & Wildfeuer & LucaLuca & Steve Sanders / wikimedia

It should be noted that the four o'clock flower is a species that canself-sow and reproduce, growing rapidly in tropical regions with ample sunlight, warm climate, and sufficient water. If not controlled, it will escape from gardens into the wild and become a naturalized plant.

At present, the four o'clock flower has spread to many places in Asia, Africa, North America, Europe, and elsewhere, and even grows in large patches on some tropical islands and warm, humid coasts, becoming a dominant invasive plant and seriously affecting the growth of local plants.

This article is the 247th article of Year 4 of Species Calendar, from Species Calendar author @Banna Hualun Jun.

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