Japanese madder (Akane), European madder (Akane serrata), and Indian madder (Akane umbellata) all belong to the genus Rubiaceae, and are well-known for their roots being used primarily for red dyeing. The color "akane-iro" (madder red) is derived from the plant "akane," and is also frequently used in personal names. Even though its use has declined, it remains a well-known Japanese word. However, few people may be familiar with the plant itself. Furthermore, while the three species mentioned above are generally known in the dyeing industry, descriptions often confuse them considerably. When distinguishing these three species, the number of leaves growing from a single point, the thorns on the stem, and the color of the flowers are important. Although all three are used for dyeing, their histories differ significantly. This is likely due in part to the significant differences in the chemical composition of the three species. Because of these differences in composition, the "akane-iro" of Japan is actually different from the "akane-iro" of other countries. This article will explain the classification, uses, and chemical composition of the genus Rubiaceae.

What are madder, European madder, and Indian madder?

Rubia argyi, also known as Japanese madder, is a climbing perennial herb distributed in Honshu, Shikoku, and Kyushu in Japan; as well as in Korea, Taiwan, and southern China, growing in forest edges and thickets (Kanagawa Prefecture Flora Survey Association, 2018). In Japan, it has been used for dyeing. Although its use has declined, it can still be commonly found in the wild.

Rubia tinctorum, also known as European madder, is a climbing perennial plant distributed in Europe and North Africa. It was cultivated for dyeing purposes throughout the world, mainly in West Asia, Central Asia, and South Asia, and has since escaped cultivation in various regions (RBG Kew, 2023). In Japan, the plant itself is rarely cultivated, mainly in botanical gardens.

Indian madder (Rubia manjith) is a climbing perennial plant distributed in southern China, Nepal, and India. It has been cultivated primarily for dyeing purposes, mainly in its native regions.

Both belong to the genus Rubia in the family Rubiaceae, and it is well known that their roots have been used primarily for dyeing red colors. In fact, European madder was used as a food additive in Japan until 2004. The color "akane-iro" (madder red) is derived from the plant "akane," and it is also a common personal name. Even though its use has declined, it remains a well-known Japanese word. The names of insects such as "akiakane" (autumn madder) and "natsuakane" (summer madder) are derived from the color, but these names would not have been given without akane.

What kind of dragonfly is a "red dragonfly"? Why does it turn red? Why does the common skimmer dragonfly turn blue? Two scientific reasons have been revealed. It turns out it's actually "sunscreen"!?

The "red dragonfly" is a creature so familiar to Japanese people that it even has its own children's song. The group commonly referred to as "red dragonfly" is a general term for dragonflies whose males turn red. Taxonomically, it's not a single group but rather a collective term for several separate groups, such as the Sympetrum and Scarlet Skimmer genera.

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However, few people may know about madder as a plant. The genus madder is characterized by its stipules, which are the same shape as the leaves, appearing as if 4 to 10 leaves are arranged in a whorl, its flowers are stalked, its corolla is 5-lobed, and its fruit is a siphon.

While the three types mentioned above are generally known in the dyeing and finishing industry, there is a considerable amount of confusion in their descriptions. In particular, what is actually madder is often referred to simply as "madder."

What are the differences between Japanese madder, European madder, and Indian madder?

Biologically, *Sympetrum frequens*, *Sympetrum parvulum*, and *Sympetrum indica* are completely different species (Wu et al., 2011).

As a fundamental premise, as mentioned above, the distribution differs in Japan, Europe, and South Asia, and originally, the types of dyes used varied depending on the region.

Morphologically, all members of the genus Sympetrum have leaves (more precisely, leaves and stipules) arranged in whorls, but while Sympetrum frequens and Sympetrum indica have four leaves in their whorls, Sympetrum parvifolium has six.

Furthermore, regarding the leaf veins, there is a difference between madder and Indian madder, which have palmate venation (veining that runs palmately from the base of the leaf), and European madder, which has pinnate venation (the typical venation composed of a main vein and lateral veins).

The difference between madder and Indian madder is that madder has downward-pointing thorns on its stem, while Indian madder does not.

Furthermore, regarding the flowers, there is a difference in that the flowers of *Rubia japonica* are white, while those of *Rubia nigricans* are red.

Based on the above, you should be able to distinguish between the three species as plants.

In addition, Japan has other species such as Rubia cordifolia var. lancifolia and Rubia hexaphylla, but both have leaves arranged in whorls of 6 to 8, and Rubia jesoensis can be distinguished from it by its upright growth rather than its climbing habit.

What are the differences in uses between the Japanese madder (Rubia japonica), European madder (Rubia nigrofasciata), and Indian madder (Rubia japonica)? Did they actually decline during the Heian period?!

Russula madder, Rubia verna, and Rubia tinctoria have all historically been used to extract pigment from their roots and dye cloth. The name "Akane" comes from the Japanese word for "red root." Its use seems to have developed independently in Japan, Europe, and India. However, nowadays, the use of these plants simply for dyeing cloth has declined.

Madder is one of the oldest red dyes used in Japan. It is already mentioned in written records in the Kojiki (compiled in 712), which was written during the Nara period (Gocho et al., 2023), but it is highly likely that it was used even earlier. Its color changes to various shades through chemical reactions; it becomes reddish-purple with lye mordant, scarlet with aluminum mordant, and red with the combined use of alkali and aluminum (Toko and Komashiro, 2007). During the Heian period, it was also used to dye armor and helmets, perhaps with the aim of boosting morale.

However, the madder dyeing technique was time-consuming and difficult, so it declined from around the late Heian period, and dyeing shifted to safflower (Carthamus tinctorius var. spinosus) and sappanwood (Biancaea sappan). In other words, the Japanese method of dyeing with madder has now become a "lost technology."

Rubia verniciflua has been cultivated as a dye in Central Asia and Egypt since ancient times, with records dating back to 1500 BC. Its use in the tomb of Pharaoh Tutankhamun is a particularly noteworthy example (Pfister, 1937). Records of its use in Europe are later, but the oldest known use is in textiles unearthed from the tomb of Merovingian queen Arnegundis in Paris, dating from 565 to 570 AD. The British New Model Army (the army of the English Civil War) also used it.

When mixed with clay and treated with alum and ammonia, it becomes "madder lake." Japanese madder produced a crimson color, but the color dyed with European madder is called "garance."

As for madder, it was used for a long time, perhaps because its production method was simpler than that of madder, and it was cultivated until the 19th century. However, in 1869, a German chemist chemically synthesized alizarin, the main component of madder dye, and from 1871 onwards it began to be produced industrially, leading to a decline in the cultivation of madder.

Although alizarin has largely been replaced by quinacridone pigment, a more lightfast pigment developed by DuPont in 1958, it has now found a use in biochemical assays to quantitatively determine the presence or absence of calcification by osteogenic cells using colorimetric methods (Smith et al., 2018). In other words, the presence or absence of bone can be confirmed using alizarin. This can be considered an important application.

In Japan, the red pigment from madder was used as a food additive under the name "madder dye," but it was banned in 2004 due to suspected carcinogenicity.

Finally, regarding Indian madder, cotton dyed with madder has been unearthed from the ruins of Mohenjo-daro (3000 BC) in India, indicating its use since ancient times. It is known as "manjishtha" in Sanskrit and was used by monks to dye their clothes.

What are the differences in composition and color between Japanese madder, European madder, and Indian madder?

Are there differences in the pigment components extracted from madder, European madder, and Indian madder?

There is a significant difference between these two (Oshita & Sakamoto, 2014).

Madder contains purpurin and mundistin as its main components, and pseudopurpurin as a secondary component.

Rubia vernalis contains alizarin as its main component, and rubiadin and alizarin glycosides as secondary components.

Indoor madder contains alizarin and purpurin, and its main component is anthraquinone-based pigment.

Therefore, there are also differences in color.

In the case of madder and rufous-green madder, the fibers are dyed red, while in madder, they are dyed a yellowish-red.

Considering this, it's safe to say that while both Japanese madder red and Western garance are in the red family, they are distinct.

References

Hiromi Gocho, Midori Muta, Mai Tsukazaki, and Miyuki Shiobara. 2023. Dyeing Methods and Color Characteristics in the Heian Period. Annual Report of the Institute for Literary Studies, Women's University 42: 1-12. ISSN: 0910-0679, https://doi.org/10.34388/1157.00002449

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Oshita, Koji & Sakamoto, Akane. 2014. A Study on the Dyeing Behavior of Madder Dye. Journal of Cultural Heritage Informatics, Kibi International University Center for Cultural Heritage Research Bulletin 11: 21-24. ISSN: 1349-1628, https://www1.kiui.jp/pc/bunkazai/kiyo11/04_oshita_pp21-24.pdf

Pfister, R. 1937. Les textiles du tombeau de Toutankhamon. Revue des Arts Asiatiques 11(4): 207-218. ISSN: 0995-7510, https://www.jstor.org/stable/43475067

RBG Kew. 2023. The International Plant Names Index and World Checklist of Vascular Plants. Plants of the World Online. http://www.ipni.org and https://powo.science.kew.org/

Smith, WL, Buck, CA, Ornay, GS, Davis, MP, Martin, RP, Gibson, SZ, & Girard, MG 2018. Improving vertebrate skeleton images: fluorescence and the non-permanent mounting of cleared-and-stained specimens. Copeia 106(3): 427-435. https://doi.org/10.1643/CG-18-047

Toko, Yukiko & Komashiro, Motoko. 2007. Natural red dyes. Journal of Life Engineering Research 9(1): 136-139. http://hdl.handle.net/10083/3267

Wu, ZY, Raven, PH, & Hong, DY (Eds.). 2011. Flora of China (Vol. 19 Cucurbitaceae through Valerianaceae, with Annonaceae and Berberidaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis. ISBN: 9781935641049

Both Paederia scandens and Paederia japonica are climbing herbs belonging to the genus Paederia in the family Rubiaceae. They are well-known for emitting a strong foul odor when their leaves are crushed, but the overall shape of the leaves of the two species is similar, and the flowers are exactly the same. Due to confusion in classification, they may be confused, but they can be distinguished by checking the gloss and hairs of the leaves. Paederia japonica is a variety of Paederia scandens, and many other varieties and cultivars are known. The foul odor comes from methanethiol, which acts as an allelopathy to protect the plant. The flowers are tubular florets with a striking contrast between white and reddish-purple in the center, and almost all bees visit these small tubes, with small bees, mainly from the family Apidae, being particularly important. The fruit is a drupe, a spherical fruit that turns yellowish-brown when ripe, and is a favorite food of birds, although the specific types of birds that eat it are largely unknown. This article will explain the classification, toxicity, pollination ecology, and seed dispersal of the genus Paederia.

What are Paederia scandens and Paederia scandens?

Paederia foetida, also known as "hot vine" or "early maiden vine," is a climbing perennial herb widely distributed in Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan, as well as Southeast Asia, growing in forest edges and thickets (Kanagawa Prefecture Flora Survey Association, 2018). It is also commonly seen in urban areas. It has naturalized in the southern United States and Hawaii, becoming a problem as an invasive species (Liu et al., 2006).

Paederia scandens var. maritima, also known as Hamasaotomekazura, is a perennial vine that grows along the coast and is distributed throughout Honshu, Shikoku, Kyushu, and Amami in Japan.

The Japanese name comes from the fact that crushing the leaves and other parts of the plant releases a strong, foul odor, and it is said that the name originally meant "fart vine," which later evolved from "hekusa" (fart odor).

Both are climbing herbs belonging to the genus Paederia in the family Rubiaceae. However, some may become woody. They are remarkably similar in that their leaves are entire and narrowly ovate to broadly ovate, and their flowers are bell-shaped with shallowly five-lobed tips and a hairy, purple center. Combined with the confusion in their classification, they may sometimes be mistaken for each other.

What is the difference between Paederia scandens and Paederia japonica?

Hamasaotomekazura is considered to be a coastal variety of Hekusokazura. Therefore, there are only slight differences between Hekusokazura and Hamasaotomekazura. Saotomekazura is another name for Hekusokazura.

The reason why the scientific names differ is that researchers have been slow to make scientific name changes (different classifications).

The only difference between Paederia scandens and Paederia scandens is in their leaves.

The difference between Paederia scandens and Paederia japonica is that Paederia scandens has thin, somewhat hairy, and dull leaves, while Paederia japonica has thick, hairless, and glossy leaves.

These forms are typical adaptations for reflecting sunlight on sunny coastlines.

No differences have been observed in the morphology of other flowers or plants.

What are the varieties and cultivars of Paederia scandens?

Many other varieties and cultivars of Paederia scandens are known.

P. scandens var. mairei f. microphylla (also known as narrow-leaved pygmy flower) has narrow leaves with a rounded base, but the leaf width varies continuously and cannot be clearly distinguished.

P. scandens f. velutina has leaves that are oblong-ovate with a heart-shaped base and are covered in many hairs, although some have intermediate characteristics.

P. scandens var. longituba has long-ovate leaves with a heart-shaped base and a flower tube that is more than three times its width, but this is actually just a variation in species. There are also other types of P. scandens, such as the slender-leaved type and the velvety-leaved type, making it difficult to distinguish them clearly.

P. scandens f. rubescens is characterized by its striking reddish-purple color on both the outer and inner surfaces, even while still in bud (Asai, 1988).

Paederia scandens f. microphylla is distributed in only two locations: Miyajima and Kinkasan (Gifu City, Gifu Prefecture). Its leaves are smaller than those of the basic species Paederia scandens. Although its scientific name overlaps with Paederia scandens, it appears to be a different species.

The author has not yet confirmed the description of Paederia scandens var. villosa. It is distributed south of Okinawa and in Taiwan (Genkei, 1955).

P. scandens var. maritima f. rubrae-stellaris is a variety of P. scandens var. maritima in which the five-lobed part of the corolla is reddish-purple, giving it a star-like appearance.

The scientific names of the above varieties and cultivars are also in a state of disparate classification, similar to *Hymenophyllum spp.*, and although they all belong to the same species, the correct scientific names have not yet been adopted.

What are the components that cause the foul odor of the Japanese honeysuckle (Paederia scandens)?

What components contribute to the foul odor that gave the plant its Japanese name?

The distinctive malodorous component is methanethiol (methyl mercaptan), which is known to be produced when pederoside, a substance found in Paederia scandens, is broken down by enzymes (Fujii, 2019).

This foul-smelling component is thought to be an allelopathic mechanism that protects the plant from pests that would otherwise damage it. In fact, you rarely see the leaves of the Japanese honeysuckle (Paederia scandens) riddled with holes.

However, the larvae of the hummingbird hawk-moth and the small hummingbird hawk-moth, as well as the recently naturalized Japanese species *Paederia scandens* and *Paederia scandens long-horned aphid*, parasitize this plant and *Paederia scandens*. It seems to have some kind of defense mechanism. The mottled white appearance of the leaves is often due to parasitism by *Paederia scandens*.

What is the shape of the flower?

The flowering period of Paederia scandens is from August to September (Hayashi et al., 2013). Short cymose inflorescences emerge from the leaf axils, bearing sparse grayish-white flowers. The corolla is bell-shaped, about 1 cm long, with five shallow lobes at the tip that spread flat. The throat and inside are reddish-purple. The inside is quite hairy.

However, as mentioned above, there are also known to be varieties with different lengths of flower tubes and different areas of reddish-purple coloration.

How is pollination done?

Because Paederia scandens is self-incompatible, it cannot self-pollinate, and cross-pollination by insects is essential (Liu et al., 2006).

What kinds of insects visit these striking reddish-purple, tubular flowers?

A study conducted in Nara Prefecture revealed a remarkable result: 100% of the bees were bees (Yokoi et al., 2008).

Many plant flowers appear to depend on a specific group of insects for pollination, but it is becoming clear that they also receive pollination from other groups of insects as a secondary factor. However, this is not the case with Paederia scandens, which is extremely dependent on bees. It has been confirmed that bees receive both nectar and pollen as rewards from Paederia scandens.

In Japanese studies that have examined specific species, examples of visits by * Hylaeus transversalis *, * Halictus aerarius*, * Lasioglossum japonicum*, and *Lasioglossum taeniolellum* have been found (Negoro, 1999). All of these bees are characterized by their small size and short tongues.

Other studies have also shown instances of visits by Amegilla quadrifasciata and Bombus diversus diversus (Matsumura, 2007), and by Xylocopa appendiculata circumvolans (Ichikawa et al., 2011). These are relatively large bees. However, it is highly likely that these visits are "nectar robbing," where the bees simply bore holes and sucked the nectar without contributing to pollination.

A study conducted in the United States, where Paederia scandens is an invasive species, also found that approximately 97% of the flowers are visited by bees, with the exception of about 3% by lepidopterans (Liu et al., 2006). While the composition varies considerably depending on the location, it appears that, similar to Japan, the majority of visitors are from the family Halicidae. However, a difference from Japan may be that European honeybees are also numerous, accounting for as much as 90% in urban areas.

Considering these results together, the shape of the flower may be best adapted to small bees, mainly those of the family Carangidae. Indeed, the size of the flower tube seems just right for small bees to enter. Since the stamens and pistils of the Japanese honeysuckle are short, it would be more beneficial for the honeysuckle if small bees with short proboscises could directly enter the flower rather than bees that use their long proboscises to collect nectar from a distance, as this would facilitate pollination.

The reddish-purple color of the corolla is thought to attract bees. The function of the hairs inside the corolla is unknown, but they may serve as a cushion or foothold for the bees.

However, as mentioned above, several varieties and cultivars with different flower sizes have been identified. This fact suggests that different populations may rely on different types of bees for pollination. Further research on this point may reveal some interesting findings.

What is the structure of the fruit?

All plants in the genus Paederia have drupe fruits. A drupe is a fruit in which the endocarp surrounding the seed hardens to form a "stone," and the mesocarp surrounding the stone is usually fleshy (pulp). It's easy to understand if you imagine a plum or apricot.

The drupe of the Japanese honeysuckle is spherical, about 5 mm in diameter. When ripe, it turns yellowish-brown. Inside, there are two kernels, each containing one seed.

What are the seed dispersal methods?

As its succulent nature and yellowish-brown color when ripe suggest, it is clearly appealing to animals, and various studies have confirmed that it is dispersed by birds (Karasawa, 1978; Takatsuki, 2021; 2023). However, since most studies have examined droppings, it is not clear which specific birds prefer it. There is only one instance where it was eaten by Japanese white-eyes in an experiment (Hirao et al., 2021).

Although the leaves of the Japanese honeysuckle wither in winter, the stems remain on other plants or fences, and the fruits remain throughout the winter. It is presumed that birds that visit the trees forage for the fruits at this time (Takatsuki, 2023).

Paederia scandens seeds do not germinate at all if the pulp is still attached, and seeds found in bird droppings have a higher germination rate than seeds with the pulp removed (Karasawa, 1982). This suggests that, in addition to the removal of the pulp by birds, some effect related to digestion, or damage to the seeds when they are pecked by birds' beaks, promotes germination. This indicates that Paederia scandens cannot survive without birds.

On the other hand, there is one known instance of a mammal, the raccoon dog, using it (Takatsuki, 2018). The fruits of the Japanese honeysuckle are very small and seem inefficient for foraging, but it is possible that mammals may occasionally use them.

References

Asai, Yasuhiro. 1988. A new variety of Akebono-yaitobana. Journal of Japanese Plant Research 63(2): 54-54. https://doi.org/10.51033/jjapbot.63_2_8125

Fujii, Yoshiharu. 2019. The strangely named plant, *Paederia scandens*, is it really that smelly? Kagaku Dojin, Kyoto. 244pp. ISBN:
9784759819892

Genkei, M. 1955. Enumeratio Tracheophytarum Ryukyu Insularum (VII). The science reports of the Kanazawa University 4(4): 45-134. https://doi.org/10.24517/00011478

Hayashi, Yasaka, Kadota, Yuichi, and Hirano, Takahisa. 2013. Yamakei Handy Illustrated Guide 1: Wildflowers (Revised and Expanded New Edition). Yama-kei Publishers, Tokyo. 664pp. ISBN: 9784635070195

Hirao, Tamon; Hirata, Reiko; and Ito, Satoshi. 2021. Effect of seed size on seed retention time within the body of a Japanese white-eye. Japanese Forest Society Conference Presentation Database 132: 449. https://doi.org/10.11519/jfsc.132.0_449

Ichikawa, S., Kurahashi, T., & Ikuru, S. 2011. Possibility of a novel pollination mode by flower-visiting bees and yellow-breasted bumblebees collected in Kagawa Prefecture. Bulletin of the Faculty of Agriculture, Kagawa University 63(116): 43-59. ISSN: 0368-5128, http://id.nii.ac.jp/1731/00003553/

Ikeda, Kenichi. 2020. Unrecorded species of true bugs (Hemiptera) in Nara Prefecture. Niche Life 8: 13-18. ISSN: 2188-0972, https://media.niche-life.com/series/008/Niche008_05.pdf

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Karasawa, Koichi. 1978. A study on the diet and seed dispersal of fruit-eating birds in urban areas. Birds 27(1): 1-20. https://doi.org/10.3838/jjo1915.27.1

Karasawa, Koichi. 1982. Germination rates of seeds of Privet japonica and Paederia scandens found in bird droppings. Birds 31(2-3): 75-76. https://doi.org/10.3838/jjo1915.31.75

Liu, H., Pemberton, RW, & Stiling, P. 2006. Native and introduced pollinators promote a self-incompatible invasive woody vine (Paederia foetida L) in Florida. The Journal of the Torrey Botanical Society 133(2): 304-311. https://doi.org/10.3159/1095-5674(2006)133[304:NAIPPA]2.0.CO;2

Matsumura, Yu. 2007. Ecology of bees—Focusing on a bee survey at Senbonmatsu Ranch—. Nasunogahara Museum Bulletin 3(1): 1-18. https://doi.org/10.34372/nasunogahara.3.1_1

Negoro, Takashi. 1999. Flower-visiting behavior of bees at Kanazawa Castle Ruins (former Kanazawa University campus). Research Report of Toyama City Science and Culture Center 22: 55-79. ISSN: 0387-9089, http://repo.tsm.toyama.toyama.jp/?action=pages_view_main&active_action=repository_view_main_item_detail&item_id=731&item_no=1&page_id=13&block_id=82

Takatsuki, Shigeki. 2018. Characteristics of fruits used by raccoons—a review. Mammalian Science 58(2): 237-246. ISSN: 0385-437X, https://doi.org/10.11238/mammalianscience.58.237

Takatsuki, Seiki. 2021. Seed dispersal by birds to persimmon trees on the Azabu University campus. Azabu University Journal 32: 1-9. ISSN: 1346-5880, http://id.nii.ac.jp/1112/00005374/

Takatsuki, Seiki. 2023. Fruiting patterns of isolated urban trees and seed dispersal by birds: An attempt at seed recovery using pavement. Conservation Ecology Research 28(1): 165-176. https://doi.org/10.18960/hozen.2130

Yokoi, Tomoyuki; Habe, Akifumi; Katori, Ikuo; and Sakuraya, Yasuyuki. 2008. Diversity of pollinating insect communities at Kinki University Nara Campus. Kinki University Faculty of Agriculture Bulletin 41: 77-94. ISSN: 0453-8889, http://id.nii.ac.jp/1391/00005214/

Gardenias are indispensable plants to the Japanese, both as wild plants, ornamental plants, and food additives. There is also a species called *Gardenia jasminoides*, and while the flower shape is the same, the leaves are opposite or in whorls of three, and both are evergreen, glossy, entire, and usually pointed at the tip. You may get confused about the distinction, but there are significant differences in tree height, leaf size, and flower size between gardenias and *Gardenia jasminoides*. Several varieties are known, including single-flowered and double-flowered types. Although widely cultivated in horticulture, it has been used in Japan since ancient times as a yellow coloring agent and is also used medicinally in traditional Chinese medicine. In single-flowered varieties, the base is tubular, the corolla is divided and white, and it has a fragrance. It is mainly pollinated by hawk moths, but other insects may also play a supporting role in pollination. The fruit is a berry with distinctive retained sepals. It is thought that birds eat the fruit and disperse the seeds, but the specific species is still unknown. This article will explain the classification, uses, pollination ecology, and seed dispersal of gardenias and small gardenias.

What are gardenias and small gardenias?

Gardenia jasminoides var. jasminoides (in the narrow sense) is an evergreen shrub distributed in Japan, west of Shizuoka Prefecture on Honshu, Shikoku, Kyushu, and the Ryukyu Islands; Korea, the Indochina Peninsula (Vietnam, Laos, Cambodia), Nepal, India, and Pakistan, growing in evergreen broad-leaved forests along coastlines and hillsides, as well as in dry Japanese red pine forests (Wu et al., 2011; Hayashi, 2019). It is also cultivated as an ornamental plant in Europe, North America, and the Pacific Islands.

Gardenia jasminoides var. radicans, also known as small gardenia, is native to China and is a relatively common evergreen shrub in Japan, used as a garden tree, hedge, and ground cover. However, it is not distinguished from gardenia in Chinese literature, and its exact distribution is unknown (Wu et al., 2011).

These belong to the genus Gardenia in the family Rubiaceae, specifically to the broader category of Gardenia jasminoides. Therefore, they are considered the same species, with few significant biological differences, and the differences are thought to be at the variety level.

Therefore, there is no difference in the shape of the white single or double flowers, the leaves are opposite or in whorls of three, and as they are evergreen trees, they are glossy, have entire margins, and the tips of the leaves are usually pointed. Someone seeing them for the first time might not be able to tell the difference.

What is the difference between gardenia and small gardenia?

These two varieties exhibit clear morphological differences (Hayashi, 2019). However, the main difference is in size.

Firstly, the leaves of the common gardenia are clearly large, measuring 6-17 cm in length, while those of the small gardenia are clearly smaller, measuring 2.5-7 cm in length.

Furthermore, in gardenias, the lateral veins of the leaves are prominent and the spaces between the veins are swollen, whereas in gardenias jasminoides, the lateral veins are not prominent and the spaces between the veins are smooth.

While the flowers of the common gardenia are large, measuring 5-7 cm in diameter, those of the small gardenia are smaller, measuring 3-4 cm in diameter.

While gardenias can grow to a height of 1-2 meters (up to 5 meters in subtropical regions), small gardenias only reach about 30-50 cm.

What is the variety of gardenia?

As explained above, it is easy to distinguish between gardenias and small gardenias, but there are varieties that differ in whether the flowers are single-petaled or double-petaled, and other forms.

Sometimes, the Japanese and scientific names are determined by whether the flowers are single-petaled or double-petaled, but the relationship between them is a bit complicated.

The original gardenia species has single flowers, while the double-flowered variety is called Yaekuchinashi 'Flore-pleno'.

However, the original species of gardenia, f. radicans, is considered to have double flowers, while the single-flowered variety is called gardenia f. simpliciflora.

This difference stems from the order in which the scientific names were assigned, but unless you're a plant enthusiast, you probably don't need to be particularly aware of it.

Other known varieties of gardenia include 'Albomarginata', which has white margins on the outer edges of its leaves; 'Maruba', which has rounded leaf tips; and 'f. globicarpa ', which has small, spherical fruits about 1.2 cm in diameter (Sakata, 1958).

How do I use it?

Gardenias and small gardenias are frequently cultivated for ornamental purposes.

However, it is perhaps best known for its use as a coloring agent. The ripe fruit contains carotenoid pigments called crocin and crocetin, and in Japan it was originally used as a dye for textiles. The use of gardenia as a dyeing agent in Japan dates back at least to the Kofun period (Sato, 1999), as evidenced by the detection of gardenia pigment components in fiber fragments excavated from the Shimoikeyama Kofun in Nara Prefecture (Sato, 1999). Powdered dried fruit has been used since the Nara period, and in the Heian period it was called gardenia color and used to dye clothing such as the twelve-layered kimono.

Even today, it is used as a harmless natural pigment in dishes such as chestnut paste for New Year's celebrations. As a food additive, it is labeled as "gardenia pigment" and is used to color sweet potatoes, chestnuts, Japanese sweets, and pickled radishes yellow. Genipin, which is formed in the intestines from geniposide, a type of iridoid glycoside, can also be used as a blue pigment.

It is also used medicinally, with crocetin and genipin contained in the fruit being considered medicinal components (Yagi et al., 2021). When dried in the sun or in the shade, it is called "Shan Zhi Zi" and is used as an anti-inflammatory and hemostatic agent, treating congestion and inflammation, and is used for jaundice, vomiting blood, etc. It is prescribed in traditional Chinese medicine for the same purpose (Shirataka, 2018). It is also said to have an effect of dilating narrowing of the bile ducts and intestinal tracts.

In recent years, flowers have also been used as essential oils because of their pleasant fragrance.

What is the structure of a flower?

Gardenias bloom from June to July, producing fragrant flowers individually on short stalks emerging from the leaf axils. The flowers are 5-8 cm in diameter, with tubular calyxes and corolla bases. The corolla is initially white but gradually changes to a yellowish color. While usually single-flowered, there is also a double-flowered variety called 'Flore-pleno'. In single-flowered varieties, the corolla is divided into 6 or 5-7 lobes. There are 6 stamens containing numerous pollen grains and one thick pistil. The stamens grow parallel to the corolla. The sepals are long and slender, and there are 6 of them.

The only difference between the common gardenia and the small gardenia is that the flowers are 3-4 cm in diameter.

How is pollination done?

Gardenias are clearly pollinated by insects, but research on the insects that visit them is not well done.

However, the gardenia flower has a tubular base, requiring a very long, straw-like mouthpart to suck nectar, and it has a strong scent and is white in color, which are typical characteristics of flowers pollinated by hawk moths. Several studies have suggested that it is pollinated by hawk moths (Okamoto et al., 2008; Raju et al., 2022). Hawk moths are a species of moth with an extremely long proboscis that is active from evening to night. The way its color changes is also very similar to that of honeysuckle, which is pollinated by hawk moths.

What are the differences between honeysuckle, dwarf honeysuckle, beach honeysuckle, and golden honeysuckle? We'll explain how to distinguish between similar species! Why do their flowers have different shapes? Why do some bloom in the evening?

Japanese honeysuckle (Lonicera japonica) is the most common species in Japan, frequently found both in the wild and in gardens. Several closely related species are known, and four species—Japanese honeysuckle (Lonicera japonica), Japanese honeysuckle (Lonicera japonica var.

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On the other hand, there have been a few instances of the Ryukyu longhorn beetle visiting the plants (Chaki and Mizunaga, 2021), suggesting that, like honeysuckle, the plants may be pollinated by groups of multiple insects.

Furthermore, it is known that small insects such as Thrips hawaiiensis and Frankliniella intonsa come to feed on pollen (Kurosawa, 1968; Takahashi, 1984), and I myself have observed them swarming in countless numbers on numerous occasions.

Because thrips are very small, a single thrips doesn't carry much pollen. However, at certain times of the year, thrips become adults in 1-2 weeks and go through several generations during a single flowering season, resulting in a large number of individuals that can potentially contribute as pollinators. In the case of the Habenaria radiata, which is also pollinated by hawk moths, there are records of thrips contributing to the pollination of 1/4 of all the seeds produced (Shigeta & Suetsugu, 2020). However, a disadvantage is that they move pollen within the flower in order to eat it, which can encourage self-pollination. Although not yet verified, thrips may also play a role in auxiliary pollination in gardenias.

What species resembles the egret orchid? The flowers are visited by hawk moths! And not only that, tiny insects called thrips also play an important role in pollination! What is the "Egret Orchid Legend"?

The egret orchid (Habenaria radiata) is a perennial plant that inhabits slightly damp areas and is a popular choice for gardening. Unfortunately, due to the decline of its wetland habitat and illegal harvesting, it is listed as near-threatened on the Ministry of the Environment's Red List. There are many closely related species, and many that share the name "egret orchid," but this particular species has a flattened stem resembling a heron...

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What is the structure of the fruit?

The fruit of the gardenia is a fleshy berry. It is oval-shaped, 2-3 cm long, with 5-7 ridges, and because the ovary is inferior, the sepals remain at the top. It ripens to an orange color at the end of autumn. The double-flowered variety 'Flore-pleno' is said not to bear fruit. However, wild populations have been confirmed in some areas, and these have been shown to bear fruit (Miyazaki et al., 2016). Numerous seeds are embedded in the pulp, and they are medium-sized, oval-shaped, and flattened.

What about seed dispersal?

The orange color of gardenia fruit is due to carotenoid pigments called crocin and crocetin, which are also components of the pigment found in the pistils of saffron (Ichi et al., 1993).

The fruit clearly turns orange, suggesting that birds with well-developed vision and a response to red are attracted to it. Therefore, it is believed that the seeds are dispersed by birds (Miyazaki et al., 2016; Morisada et al., 2020), but it seems that no specific research has been conducted on which birds contribute to seed dispersal. The characteristic of fleshy berries being dispersed by birds is widely observed in the Rubiaceae family (Bremer & Eriksson, 1992).

It is thought that the medicinal properties of geniposide may be a way to avoid being eaten by mammals, but there is no research on this.

References

Bremer, B., & Eriksson, O. (1992). Evolution of fruit characters and dispersal modes in the tropical family Rubiaceae. Biological Journal of the Linnean Society, 47 (1), 79-95. https://doi.org/10.1111/j.1095-8312.1992.tb00657.x

Chaki, Keita & Mizuru, Naoki. (2021). *Ryukyu longhorn beetle* visiting gardenia flowers at night. *Gekkan Mushi*, 608, 58. ISSN: 0388-418X

Hayashi, Masayuki. (2019). Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers. ISBN: 9784635070447

Ichi, Takahito; Katayama, Go; and Tada, Mikio. (1993). Changes in carotenoid patterns associated with the development of gardenia fruit. Bulletin of the Faculty of Agriculture, Okayama University, 82, 9-15. https://ousar.lib.okayama-u.ac.jp/905

Kurosawa, M. (1968). Studies on Japanese thrombi. *Insecta Matsumurana Supplement *, 4, 1-92. http://hdl.handle.net/2115/22225

Miyazaki, Hiroshi; Kanaya, Seiichi; Kawahara, Noriyuki; Matsunaga, Jun; and Matsunaga, Michio. (2016). Origin and characteristics of the existing "Tatsutayama Yaekuchinashi". Research Report of the Forestry and Forest Products Research Institute, 15 (3), 81-90. https://doi.org/10.20756/ffpri.15.3_81

Mori, S., Nozaki, T., Ogawa, M., & Kamada, M. (2020). Succession process from Japanese black pine forest to evergreen broad-leaved forest in Ogihama, Kochi Prefecture. Landscape Ecology, 25 (1), 75-86. https://doi.org/10.5738/jale.25.75

Okamoto, T., Kawakita, A., & Kato, M. (2008). Floral adaptations to nocturnal moth pollination in Diplomorpha (Thymelaeaceae). Plant Species Biology, 23 (3), 192-201. https://doi.org/10.1111/j.1442-1984.2008.00222.x

Raju, AS, Kumar, SS, Grace, LK, Punny, K., Raliengoane, TP, & Prathyusha, K. (2022). Zoophily and nectar-robbing by sunbirds in Gardenia latifolia Ait. (Rubiaceae). Journal of Threatened Taxa, 14 (8), 21642-21650. ISSN: 0974-7893, https://doi.org/10.11609/jott.7930.14.8.21642-21650

Sakata, Toshio. (1958). A brief record of plants native to Japan. Journal of the Botanical Garden, 33 (1), 28-32. https://doi.org/10.51033/jjapbot.33_1_4218

Sato, Masanori. (1999). Advances in scientific research methods for culturally significant dyed textiles. Journal of the Textile Society of Japan, 55 (7), 216-221. https://doi.org/10.2115/fiber.55.7_P216

Shigeta, K., & Suetsugu, K. (2020). Contribution of thrips to seed production in Habenaria radiata, an orchid morphologically adapted to hawkmoths. Journal of Plant Research, 133 (4), 499-506. ISSN: 0918-9440, https://doi.org/10.1007/s10265-020-01205-z

Shirataki, Yoshiaki. (2018). Wildflowers of the Mountains and Fields—Edible and Medicinal Properties of Common Wild Plants—Gardenia. New Food Industry, 60 (7), 56-58. https://libir.josai.ac.jp/il/user_contents/02/G0000284repository/pdf/JOS-05470277-60(7)-56.pdf

Takahashi, Asao. (1984). Ecology and control methods of thrips that damage the inside of fig fruits. Plant Protection, 38 (10), 450-453. ISSN: 0037-4091, http://jppa.or.jp/archive/pdf/38_10.pdf#page=14

Wu, ZY, Raven, PH, & Hong, DY (Eds.). (2011). Flora of China (Vol. 19 Cucurbitaceae through Valerianaceae, with Annonaceae and Berberidaceae). Science Press, and Missouri Botanical Garden Press. ISBN: 9781935641049

Yagi, M., Sakiyama, C., Miyata, Y., Kamiya, S., & Yonei, Y. (2021). Antiglycative effect of genipin and crocetin. Glycative Stress Research, 8 (3), 156-161. ISSN: 2188-3602, https://doi.org/10.24659/gsr.8.3_156