Amachazuru is a perennial vine that grows in mountainous areas and thickets in Japan, but it is often confused with other species such as Yabugarashi and Amacha (sweet tea). Both Amachazuru and Yabugarashi have palmate compound leaves and their fruits are berries, so they are similar, and Amachazuru and Amacha also have similar names. However, they are all completely different in classification, and Amachazuru and Amacha are different in every way except for their uses. You can distinguish between Amachazuru and Yabugarashi by carefully examining the shape of their palmate compound leaves and the hairs. This article will explain the classification, uses, and morphology of Amachazuru.

What are Amachazuru, Yabugarashi, and Amacha?

Gynostemma pentaphyllum, also known as Amachazuru or Narrow-leaved Indigo, is a climbing perennial herb distributed in Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea, China, and Malaysia, growing in mountainous areas and thickets (Hayashi et al., 2013; Kanagawa Prefecture Flora Survey Association, 2018).

Cayratia japonica, also known as Japanese bush lily (or bush killer), is a climbing perennial herb widely distributed in southwestern Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea, China, India, and Malaysia, growing in bushes and cultivated fields. It is sometimes called "Yabugarashi," but the botanical Japanese name is "Yabukarashi" without the voiced consonant mark.

Amacha (sweet tea), Hydrangea serrata var. thunbergii, is thought to be a variety of Hydrangea serrata (in the broad sense) with smaller leaves (Hayashi, 2019). Therefore, it is a deciduous shrub that looks almost exactly like a hydrangea. It is distributed in Honshu, Japan (Kanto and Chubu regions), but there is also a theory that it is originally a cultivated variety. It grows along valleys in mountainous areas.

Amachazuru and Yabukarashi may be similar because both have palmate compound leaves and their fruits are berries that ripen to black.

Also, Amachazuru and Amacha (sweet tea) have similar names, so people unfamiliar with them might not be able to tell them apart.

What are the differences between Gynostemma pentaphyllum, Cayratia japonica, and Gynostemma pentaphyllum?

However, these three species are completely different in terms of classification.

First, Gynostemma pentaphyllum belongs to the Cucurbitaceae family, Cayratia japonica belongs to the Vitaceae family, and Hydrangea macrophylla belongs to the Hydrangeaceae family. At this point, you can expect there to be significant differences in their morphology.

There are countless differences between Gynostemma pentaphyllum and Hydrangea serrata. In fact, the only similarities are their names and uses. The leaves of Gynostemma pentaphyllum are palmate compound leaves, while those of Hydrangea serrata are ordinary simple leaves. As the classification suggests, the flowers of Hydrangea serrata closely resemble those of hydrangeas. The fruit of Gynostemma pentaphyllum is a berry, while that of Hydrangea serrata is a capsule.

While the leaves of Gynostemma pentaphyllum and Cayratia japonica are indeed very similar, Gynostemma pentaphyllum has hairs on the upper surface of its leaves and short petioles (the thin parts that connect one leaflet to another), whereas Cayratia japonica has hairless upper surfaces and long petioles, especially the petiole of the uppermost terminal leaflet, which is more than a quarter the length of the leaf blade of the terminal leaflet.

The flowers are completely different. Amachazuru has small, yellowish-green flowers arranged in racemes, with fused petals that are five-lobed and have pointed, tail-like tips, while Yabugarashi has cymose inflorescences that are open and saucer-shaped, with nectar coming from an orange part called the floral disc, and is a separate-petaled flower with four pale green petals.

The fruits are somewhat similar, but the difference is that the fruits of Gynostemma pentaphyllum hang downwards, while those of Cayratia japonica protrude upwards.

With the above information, you shouldn't mistake them for each other. For differences between hydrangeas and wild grapes (Vitis coignetiae), please see our other articles.

What's the difference between Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae)? We explain how to distinguish between similar species! Why are they exterminated? Are they actually edible? Were the wasps that visit the saucer-shaped flowers hired as bodyguards?!

Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae) are among the most common climbing plants in the grape family. While they belong to the same family and are both climbing plants, they can be easily distinguished by the shape of their leaves and flowers. Japanese knotweed is a target for eradication due to its strong reproductive capacity, impact on the landscape, and its ability to attract bees...

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What are the differences between hydrangeas, lacecap hydrangeas, mountain hydrangeas, oakleaf hydrangeas, and American hydrangea (Annabelle)? We explain how to distinguish between similar varieties! Most of the flowers are just "decorations"!? What do the fruits, which are rarely seen, look like?

Hydrangeas, lacecap hydrangeas, mountain hydrangeas, oakleaf hydrangeas, and American hydrangeas (Annabelle) all belong to the genus Hydrangea in the family Hydrangeaceae, and are commonly cultivated and found in urban areas. Hydrangeas, in particular, are arguably representative of Japan. All of them develop large calyxes around the rainy season...

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What are the differences in how Amacha (sweet tea) and Amachazuru (Gynostemma pentaphyllum) are used?

Although Amacha (sweet tea) and Amachazuru (Gynostemma pentaphyllum) have similar names, this is due to their common uses.

In the case of Amacha, young leaves are harvested in late August, sun-dried, sprayed with water, packed into barrels, and fermented for 24 hours. These leaves are then steamed, kneaded, dried again, and brewed to produce "Amacha." It is a type of tea in a broad sense.

With Gynostemma pentaphyllum, a beverage is made by extracting the leaves or the entire plant with hot water. This is also sometimes called "amacha," but the tea made using "amacha" is the original amacha.

While both are considered luxury items, Amacha is different in that it is fermented, whereas Amachazuru is not.

Furthermore, in terms of intended use, Amacha has a strong connection to Buddhism, as it has been traditionally used since the Edo period to pour a sweet drink over Buddha statues during the Kanbutsu-e (Flower Festival) to celebrate the birth of Gautama Siddhartha (Buddha/Shakyamuni), following historical precedent (Kobayashi, 1999). However, Amachazuru, which has been called "Shibori-mata-ai" since ancient times, has only been used as a folk remedy for inflammation, detoxification, cough suppression, expectoration, and chronic bronchitis since ancient times, which is a significant difference (Bu et al., 2018).

However, amacha is not without medicinal properties. In folk medicine, it is used as a sweetener for diabetic patients and as a tea to treat weak stomachs, loss of appetite, diuresis, and bad breath. It is said to have antitumor, anti-allergic, antibacterial, and choleretic effects (Yamahara et al., 1994). Filodulcin and isophyllodulcin are the source of its sweetness and are not digested or absorbed, making it calorie-free. As a sugar substitute, it has attracted attention and is used by diabetic patients (Fujii & Yoshida, 2005; Kojima et al., 2018).

However, in rare cases, there have been instances of food poisoning caused by amacha in Kanagawa Prefecture in 2009 and 2010 (Kojima et al., 2018). It is puzzling that amacha, which has a long history of being consumed as a beverage, would cause food poisoning, and although the causative substance has not been identified, it has been suggested that it may have been brewed and consumed in a way that contained a high concentration of bitter components, so caution is advised in this regard.

What is the structure of a flower?

Gynostemma pentaphyllum flowers from August to September. It is dioecious (having separate male and female plants). Small, yellowish-green flowers, about 5 mm in diameter, bloom in racemes in the leaf axils. The corolla is 5-lobed and tapers to a point at the tip. The calyx is small.

While Japanese knotweed (Cayratia japonica) can reproduce asexually using its rhizomes, it does flower from June to August. It forms cymose inflorescences, and the flowers are open and saucer-shaped, secreting nectar from an orange part called the floral disc. They are initially reddish and later change to orange. The flowers are 5 mm in diameter, with four pale green petals, four stamens, and one pistil. After initially producing stamens, it undergoes a sex change and produces a pistil, a process called "protandry" that prevents self-pollination.

Hydrangea serrata flowers from June to July. Its inflorescence consists of inconspicuous "hermaphrodite flowers" that later produce seeds, and "decorative flowers" that are located on the periphery of the inflorescence, lacking petals and composed only of sepals, which only increase its appeal to insects and do not produce seeds. The decorative flowers are purplish to reddish, and their sepals are circular to broadly ovate and overlap. The hermaphrodite flowers are blue.

What is the structure of the fruit?

The fruit of Gynostemma pentaphyllum is a berry, spherical in shape about 7 mm in diameter, and ripens to a dark green color. The remnants of the calyx and corolla remain in a ring shape.

The fruit of Cayratia japonica is a berry, spherical, rarely somewhat rounded, and ripens to black. However, while the diploid variety distributed west of the Kanto region readily bears fruit, the triploid variety distributed east of the Kinki region and more common in eastern Japan does not bear fruit. Therefore, you may not often have the opportunity to see the fruit of Cayratia japonica.

The fruit of the Amacha plant is a capsule, ovate to elliptical in shape, 3-4 mm long, and ripens in October and November. The seeds are small and elliptical, with wing-like projections at both ends.

References

V.T. Gokuha, Hiroko Hashida, Misaki Kurawaka, Haruka Tatehana, Anna Arita, Naho Sasaki, Fumio Shimura, and Yuko Yamazaki. 2018. Examination of the safety of Gynostemma pentaphyllum products in accordance with the methods for evaluating the safety of food additives. Jumonji Gakuen Women's University Bulletin 48(2): 85-97. ISSN: 2424-0591, https://jumonji-u.repo.nii.ac.jp/records/159

Fujii, Toshio & Yoshida, Tomohiko. 2005. Characteristics of Hydrangea serrata in the Hydrangea genus. Journal of the Crop Science Society of Japan 74(1): 52-57. https://doi.org/10.1626/jcs.74.52

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

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Kojima, T., Kai, S., Kishi, H., Uemura, J., Miyazawa, M., & Satake, M. 2018. Food poisoning suspected to be caused by sweet tea. Journal of the Japanese Society for Food Science and Technology 51(2): 133-134. https://doi.org/10.11402/cookeryscience.51.133

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

Kobayashi, Mayumi. 1999. Hyakuseki Santan and the Buddha's Birthday Celebration. Seijo Kokubun Gakuronshu 26: 1-19. ISSN: 0286-9063, https://seijo.repo.nii.ac.jp/records/380

Yamahara, J., Matsuda, K., Shimoda, H., Ishikawa, H., Kawamori, S., Warishi, N., and Yoshikawa, M. 1994. Functional Development of Hydrangea macrophylla (Part 2): Anti-ulcer activity, anti-allergic activity, and choleretic activity of Hydrangea macrophylla extract. Yakugaku Zasshi 114(6): 401-413. https://doi.org/10.1248/yakushi1947.114.6_401

The Vitaceae family consists of climbing woody or herbaceous plants. They ascend by tendrils, which are modified stems, although a few genera lack tendrils. Tendrils and leaves are opposite. Leaves are alternate, simple, or compound. Simple leaves are often palmately lobed. Inflorescences are usually opposite the leaves. Flowers are bisexual, monoecious, or dioecious. Calyxes are small, cup-shaped, and 4-5 lobed. Petals are 4-5 in number, symmetrized, and unfold at flowering. Stamens are 4-5 in number, opposite the petals. Fruits are berries with soft flesh, or dried out, 2-chambered or 1-chambered, enclosing 1-4 seeds. Seeds are usually obovate with a beak, and the seed coat is hulled. In the APG system, it has been separated into a single family, the Vitales order. More than 800 species in 14 genera are known worldwide, from tropical to temperate regions.

This article provides a comprehensive, illustrated guide to plants belonging to the Vitaceae family.

The photos are replaced as soon as better ones are taken. Also, while the identification is done by the author, please note that if there are any misidentifications, they may be changed without notice.

No. 1441 European Grape Vitis vinifera subsp. vinifera

A climbing woody plant (Flora of China). Stems spread irregularly, climb high, and branch sparsely. The bark of the branches peels off in ragged pieces. The septa of the nodes are 3-5 mm thick. The twigs are cylindrical to slightly angular, hairy, and sometimes glabrous. Leaves do not develop at the growing tips. Tendrils are present from end to end of the twig and are persistent. Tendrils (or inflorescences) are present only on two consecutive nodes. The nodes are not marked with a red band. Stipules are usually 3.5 mm or longer. Petioles are approximately equal in length to the leaf blade. The leaf blade is cordate-ovate to cordate-orbicular, 12-20 cm long, usually 3 shoulders or shallowly 3-5 lobed, sometimes deeply lobed, with an acute to short acute apex. The underside is not powdery white, sparsely hairy or nearly glabrous, and hairy overall. The upper surface is normal. Flowering occurs from April to June. The inflorescence is 10–20 cm long, sparse to dense, opposite the leaves, with well-developed basal branches. The peduncle is 2–4 cm long, glabrous or sparsely covered with cobwebby hairs. The pedicel is 1.5–2.5 mm long, glabrous. The flower bud is obovate, 2–3 mm long, with a rounded apex. The calyx is glabrous and wavy. The flowers are bisexual. The filaments are thread-like, 0.6–1 mm long. The anthers are yellow, elliptical, 0.4–0.8 mm long. The pistil is immature in male flowers. The ovary is elliptical. The style is short. The stigma is spreading. Fruiting occurs from August to September. The berry is usually reddish-purple to almost black, sometimes yellowish-green, ± powdery white, spherical to oblong to elliptical, 8–25 mm in diameter (usually 15–20 mm), with the skin tightly attached to the flesh and no lenticels. The seeds are obovate to elliptic, with a nearly rounded tip, an elliptic chalazal knot, a slightly raised raphe, and a wide groove extending about a quarter of the way up from the base of the ventral cavity. While botanical distinctions between grapes are not properly documented on the Japanese internet, * Flora of North America * states that it can be distinguished from the American grape (Vitis labrusca) by its hermaphroditic flowers, oblong fruit, and pericarp attached to the pulp. Native to southwestern Asia and southeastern Europe, it was harvested by Neolithic hunter-gatherers and early farmers, and although there are various theories, it is thought to have been cultivated around 4000 BC in the Fertile Crescent alongside olives, figs, dates, and pomegranates (Diamond, 1997). Its wild species is * Vitis vinifera subsp. sylvestris *. Domestication has led to morphological changes, including larger fruit and bunch sizes, higher sugar content, altered seed morphology, and a shift from dioecious to hermaphroditic mating systems, all for the sake of human cultivation convenience and improved taste (Zhou et al., 2017). The oldest documented records can be found in the ancient Sumerian Epic of Gilgamesh, dating back to around 3000 BC. Cultivation and winemaking techniques were developed by the ancient Egyptians, Greeks, Etruscans, Phoenicians, and eventually the Romans, with grapes being cultivated particularly for wine in the Roman Empire (Charters, 2006). Wine also spread as an inexpensive and safe drinking water, but it also led to an increase in alcoholism, resulting in legal regulations on grape cultivation (Robinson, 2006). In the Middle Ages, wine was commonly consumed in southern Europe, while beer was drunk in the north and east. France and Germany (then the Holy Roman Empire), in particular, remain the largest wine-producing countries today, producing Champagne, Burgundy, and Bordeaux wines, among others. In the Americas, wine was introduced by Catholic Spain for the essential communion rituals, leading to the development of Mexican and American wines. Grapes are eaten fresh as a dessert, dried to make raisins and kneaded into bread to make raisin bread, rum-soaked raisins are used in ice cream, cakes, and chocolates, and raisin butter, made by kneading raisins into butter, is a popular snack to accompany alcoholic beverages (especially Western spirits) and is sometimes served in biscuits. In addition to grape juice and verjus (a drink made from unripe grapes), the most representative wine (grape wine) is traditionally a type of fruit wine made by fermenting the squeezed juice in barrels or jars with budding yeast Saccharomyces cerevisiae, then removing the lees, aging it in barrels for several months to several years, and finally bottling it. During aging, malolactic fermentation occurs by lactic acid bacteria such as Lacobacillus, Pediococcus, and Oenococcus oeni, converting malic acid into lactic acid, which reduces acidity (Fugelsang & Edwards, 2007), and also creates unique terroir flavors. Wine is classified into three types: white wine, which is made from grapes with light-colored skins, such as white grapes, and uses only the juice for fermentation; red wine, which is made from whole grapes, including black and red grapes, and is more astringent than white wine due to the pigments and tannins in the skins, and can be stored for a long time; and rosé wine, also called pink wine, which has a pale reddish hue and is made by blending white and red wines through various production processes.

No. 1443 Wild Vine (Vitis ficifolia)

This is a deciduous climbing woody plant (a tree with flowers). It twines around other objects with tendrils. The current year's branches are slender and initially covered in cobwebby hairs. The leaves are alternate. The leaf blade is ovate to broadly ovate-triangular, 5-8 cm long and wide. It is usually 3-5 lobed, but the degree of lobing varies greatly. The margins have shallow serrations. The base is deeply heart-shaped. The upper surface is initially covered in cobwebby hairs, but later becomes hairless. The underside is covered in light brown or white cobwebby hairs, which remain until autumn. The petiole is 2.5-8 cm long. It is dioecious (having separate male and female plants). The flowering period is from June to August. Opposite the leaves, it produces panicles 6-12 cm long, bearing small yellowish-green flowers. The petals fall off as soon as the flowers open. The inflorescences of hermaphrodite flowers are smaller than those of male flowers, and the flowers are sparsely arranged. The stamens of male flowers are long, while those of hermaphrodite flowers are short. The fruit is a berry. The fruit is spherical, about 6 mm in diameter, and ripens to black. The seeds are dark reddish-brown and about 4 mm long. It is distributed in Hokkaido, Honshu, Shikoku, Kyushu, Korea, and China. It grows in forests and forest edges from hills to mountainous areas.

No.1449 Ivy Parthenocissus tricuspidata

Also known as summer ivy. A deciduous climbing woody plant (flowers that bloom on trees). The bark is dark brown. Tendrils with suction cups at the tips extend from the nodes, allowing it to climb tree canopies and rock faces. The current year's branches are reddish-brown to yellowish-brown and hairless. They have numerous round lenticels. Short branches develop. The leaves are dimorphic; the leaves on flowering short branches are large and have long petioles. The leaf blade is broadly ovate, 5-15 cm long and wide, with three lobes at the top, the tips of the lobes are sharply pointed, and the margins have sparse serrations that become awns at the tips. The base is deeply heart-shaped. The texture is somewhat thick and almost hairless. The petiole is about 15 cm long. The leaves on long branches that do not flower are small and have short petioles. They range from unlobed to 1-3 lobed, and some have three leaflets. The flowering period is June to July. It produces cymose inflorescences 3-6 cm long from short branches, bearing numerous small yellowish-green flowers. The flowers are 2-3 mm in diameter, with 5 petals and 5 stamens. The fruit is a berry, spherical 5-7 mm in diameter, ripening to a bluish-black color in autumn. The surface is covered with a white powder. The seeds are obovate, 4-5 mm long. The winter buds are conical, 1-2 mm long, with 3-5 brown bud scales. The leaf scars are nearly circular. It is distributed in Hokkaido, Honshu, Shikoku, Kyushu; Korea; and China. It grows in forests and forest edges in mountainous areas.

No. 1451 Cayratia japonica

Also known as Japanese knotweed (Cayratia japonica). A climbing perennial herb (a wild flower). It propagates by creating long roots. The young parts have granular, protruding hairs. The stem is ridged, and the stipules are ovate-triangular and membranous. The leaves are alternate, petiolate, and consist of 5 leaflets arranged in a bird's-foot pattern. The terminal leaflet has a petiole 1-3 cm long, is narrowly ovate and pointed, 4-8 cm long, with wavy serrations, the tips of which end in small projections. The upper surface is dark green, with 6-8 pairs of lateral veins, which are depressed on the upper surface and raised on the lower surface. The lateral leaflets are smaller than the terminal leaflet and have shorter petioles. Tendrils are opposite to the leaves or inflorescence and branch at the tip. The flowering period is from June to August. The inflorescence is a flattened cyme with protruding hairs. The flowers are 5 mm in diameter. The sepals are low. The flower has four petals, ovate-triangular in shape, 3 mm long, pale green, spreading flat, with protruding hairs on the back and a mitre-shaped tip. There are four stamens with oblong anthers. The floral disc spreads flat, initially reddish, later changing to orange. There is one ovary and one style, which is columnar and erect. The berry is spherical, rarely somewhat rounded, and ripens to black. The seeds are broadly ovate, 4 mm long. Diploid varieties distributed west of the Kanto region bear fruit readily, but triploid varieties distributed east of the Kinki region and common in eastern Japan do not. It is distributed in Hokkaido (southwest), Honshu, Shikoku, Kyushu, Ryukyu Islands; Korea, China, India, and Malaysia. It commonly grows in fields and thickets.

What's the difference between Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae)? We explain how to distinguish between similar species! Why are they exterminated? Are they actually edible? Were the wasps that visit the saucer-shaped flowers hired as bodyguards?!

Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae) are among the most common climbing plants in the grape family. While they belong to the same family and are both climbing plants, they can be easily distinguished by the shape of their leaves and flowers. Japanese knotweed is a target for eradication due to its strong reproductive capacity, impact on the landscape, and its ability to attract bees...

ecological-information.com

No.1452 Ampelopsis glandulosa var. heterophylla

This is a deciduous climbing woody plant (a tree-flowered plant). It twines around other objects with bifurcated tendrils. The stems are dark grayish-brown, and the nodes are swollen. The stems die back every year, but the base becomes woody and grows to about 4 cm in diameter. The branches are initially densely covered with coarse hairs, but later become hairless. There are many circular lenticels. Tendrils emerge from each node. The leaves are alternate. The leaf blade is nearly circular, 8-11 cm long and 5-9 cm wide, and is 3-5 lobed. The tips of the lobes are pointed, and the edges have coarse, shallow serrations. The base is heart-shaped. There are sparse hairs in the vein axils on the underside of the leaf. The flowering period is from July to August. It produces cymose inflorescences opposite the leaves, bearing many small flowers. The flowers are 3-5 mm in diameter. There are 5 petals and 5 stamens, and 1 pistil. The fruit is often parasitized by the larvae of grape gall midges and grape dart wasps, forming galls and turning purple or bluish-green (this point is highly questionable; see article below). Normal fruit is rare (this is also suspicious). Seeds are 3-5 mm long. Winter buds are hidden deep within semicircular leaf scars and are not visible. Distributed in Hokkaido, Honshu, Shikoku, Kyushu, Ryukyu Islands; Korea, China, the Kuril Islands, and Ussuri. Grows in mountainous and wild areas.

What's the difference between Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae)? We explain how to distinguish between similar species! Why are they exterminated? Are they actually edible? Were the wasps that visit the saucer-shaped flowers hired as bodyguards?!

Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae) are among the most common climbing plants in the grape family. While they belong to the same family and are both climbing plants, they can be easily distinguished by the shape of their leaves and flowers. Japanese knotweed is a target for eradication due to its strong reproductive capacity, impact on the landscape, and its ability to attract bees...

ecological-information.com

No.1452.1 Ampelopsis glandulosa var. heterophylla f. citrulloides

This wild grape variety has deeply lobed leaves with indentations on the lobes resembling those of a watermelon leaf.

References

Charters, S. 2006. Wine and Society: The Social and Cultural Context of a Drink. Routledge, London. 376pp. ISBN: 9780750666350

Diamond, JM 1997. Guns, germs, and steel: the fates of human societies. W.W. Norton, New York. 480pp. ISBN: 9780393038910 [=2012. Guns, germs, and steel, Volume 1. Sōshisha, Tokyo. ISBN: 9784794218780]

Robinson, J. 2006. The Oxford Companion to Wine (3rd ed.). Oxford University Press, Oxford. 813pp. ISBN: 9780198609902

Fugelsang, KC, & Edwards, CG 2007. Wine microbiology: practical applications and procedures. Springer, Boston. 414pp. ISBN: 9780387333410

Zhou, Y., Massonnet, M., Sanjak, JS, Cantu, D., & Gaut, BS 2017. Evolutionary genomics of grape (Vitis vinifera ssp. vinifera) domestication. Proceedings of the National Academy of Sciences 114(44): 11715-11720. https://doi.org/10.1073/pnas.1709257114

Japanese knotweed (Cayratia japonica) and wild grape (Vitis coignetiae) are among the most common climbing plants in the Vitaceae family. While they belong to the same family and are both climbing plants, they can be easily distinguished by the shape of their leaves and flowers. Japanese knotweed is sometimes targeted for eradication due to its strong reproductive capacity, impact on the landscape, and its ability to attract bees. However, its ecology is fascinating; its saucer-shaped flowers are specifically designed to attract bees, relying on Japanese honeybees for pollination and hornets to remove pests from its leaves—a surprising benefit. It produces berries, which are rare in some regions, but when they are present, they are used by birds and mammals. This article will explain the classification, relationship with humans, pollination ecology, and seed dispersal of Japanese knotweed and wild grape.

Two species representative of the wild grape family

Cayratia japonica, also known as "bush killer" or "crow's strawberry," is a climbing perennial herb widely distributed in Korea, China, India, Malaysia, and Japan (southwestern Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands), inhabiting thickets and cultivated fields (Kakutani, 1994). Although sometimes called "Yabugarashi," the botanical Japanese name is "Yabukarashi" without the voiced consonant mark.

On the other hand, Ampelopsis glandulosa var. heterophylla, also known as wild grape, is distributed in Korea, China, the Kuril Islands, and Ussuri, and is a deciduous climbing woody plant that inhabits mountainous and open areas (Kanagawa Prefecture Flora Survey Association, 2018). It twines around other objects with its bifurcated tendrils, and its stems are dark grayish-brown with swollen nodes. The stems die back every year, and the base becomes woody, reaching a diameter of about 4 cm (Hayashi et al., 2013).

These two species are both climbing plants belonging to the grape family, and they share the common characteristic of producing saucer-shaped flowers. They can be frequently seen in urban plantings and the gardens of private homes.

[Seed Plant Encyclopedia #149] What are the species of the Vitaceae family? Photo list

The Vitaceae family consists of climbing woody or herbaceous plants. They ascend using modified stems called tendrils, although a few genera lack tendrils. The tendrils and leaves are opposite. Leaves are alternate, simple, or compound. Simple leaves are often palmately lobed. Inflorescences are usually opposite the leaves. The flowers are...

ecological-information.com

What is the difference between Cayratia japonica and Vitis coignetiae?

Although these two species belong to the Vitaceae family, they belong to different genera, so there is a taxonomic gap and they are easy to distinguish (Kanagawa Prefecture Flora Survey Association, 2018).

The most obvious difference is that the leaves of Cayratia japonica are "palf-foot compound leaves," meaning each leaf is divided into 3 to 9 leaflets, while the leaves of Vitis coignetiae are "simple leaves," that is, the shape of a typical, ordinary leaf.

The term "bird's foot-shaped" in "bird's foot compound leaf" refers to the way the leaf is divided, which is likened to a bird's foot (more precisely, its toenail).

Furthermore, in Cayratia japonica, the orange part called the floral disc is prominent, while in Vitis coignetiae, it is pale green and not particularly noticeable. Therefore, they can be clearly distinguished by looking at their flowers.

Incidentally, there is a variety of wild grape called *Vitis coignetiae* f. citrulloides, which has deeply lobed leaves with indentations on the lobes resembling those of a watermelon leaf. However, the leaves are still simple.

For the differences between *Cayratia japonica* and *Gynostemma pentaphyllum*, which are very similar, please see our other article.

What are the differences between Gynostemma pentaphyllum, Cayratia japonica, and Hydrangea macrophylla (Amacha)? We'll explain how to distinguish between similar species! What are their uses? What is the structure of their flowers and fruits?

Amachazuru is a perennial vine that grows in mountainous areas and thickets in Japan, but it is often confused with Japanese knotweed (Yabugarashi) and amacha (sweet tea). Both Amachazuru and Yabugarashi have similar leaves (palm-foot compound leaves) and fruits (berries), and they are quite similar...

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Why is the Japanese bush vine (Cayratia japonica) being eradicated?

Japanese knotweed (Cayratia japonica) is disliked and sometimes targeted for eradication. This is due to its vigorous growth, and its Japanese name is said to originate from the fact that it "grows so much that it covers and kills bushes."

It is also called "poor man's vine," a name that is said to originate from the fact that it is often found in neglected gardens. Perhaps it is because, as a climbing plant, its tendency to twine around things is not well-liked.

While it may be an exaggeration to say that it actually kills bushes, given its nature as a climbing plant, it is highly likely that it is depriving other plants of the opportunity to perform photosynthesis.

Eradication is difficult; even if the above-ground parts are removed, the rhizomes left in the soil will sprout again from spring to summer, and the underground stems spread horizontally, making it difficult to completely remove them from the land once they have spread.

Furthermore, as will be discussed later, it attracts wasps and hornets, which may be its greatest danger. However, it is becoming clear that there are reasons related to the Japanese knotweed (Cayratia japonica) that contribute to this.

However, since it is a very common plant, it seems that we should avoid prejudice and find a way to coexist with it through appropriate measures.

On the other hand, wild grapes don't have such a bad reputation; in fact, perhaps because their fruit is interesting, they are sometimes used for horticulture. It's a strange division in opinion.

The honey dish was exclusively for Japanese honeybees!?

Both Cayratia japonica and Vitis coignetiae produce cymose inflorescences with saucer-shaped flowers. However, their colors and structures differ subtly.

While Cayratia japonica can reproduce asexually through its rhizomes, it also flowers from June to August. Its flowers are open and saucer-shaped, and it produces nectar from an orange part called the floral disc (Kakutani, 1994; Hayashi et al., 2013). The flowers are initially reddish and later change to orange. They are 5 mm in diameter and have four pale green petals, four stamens, and one pistil. After initially producing stamens, the plant undergoes a sex change and produces a pistil, a process called "protandry" to prevent self-pollination (Kakutani, 1994; Fukuhara, 2014).

Wild grapes also bloom with saucer-shaped flowers in July and August, but the flowers are 3-5 mm in diameter and have one pistil, just like the Japanese knotweed, but they differ in that they have five petals and five stamens (Hayashi et al., 2013). Also, the floral disc remains pale green.

These saucer-shaped flowers appear to be specifically designed to attract certain insects. The saucer structure is not suitable for insects with straw-like mouths to lick the nectar, and even if they do, it would be far less efficient than flowers where the nectar is abundant deep inside the tube. Conversely, they would be very beneficial for insects with short mouths.

Regarding the two species, *Cayratia japonica*, research has been conducted on insects that actually visit it in Japan. According to the results , although a small number of insects with straw-like mouthparts, such as swallowtail butterflies and blue swallowtail butterflies, were observed, no moths or bumblebees with long mouthparts were observed at all, and the majority were bees with relatively short mouthparts (Kakutani et al., 1989; Kakutani, 1992; 1994). In addition, a small number of beetles and flies were observed.

Aside from ants, which are not considered to contribute much to pollination, the most common bee species observed was the Japanese honeybee. However, not only honeybees, but also hornets and paper wasps were the next most common.

Common sense might lead one to believe that these wasps and hornets also contribute to pollination.

However, observations revealed that among all insects, only the Japanese honeybee was found to have pollen attached to it.

Furthermore, it is said that the Japanese knotweed (Cayratia japonica) adjusts the sugar content and timing of its nectar secretion for the benefit of honeybees. Japanese honeybees are most efficient at collecting nectar when the sugar content is 60%, and the nectar of the Japanese knotweed also has a sugar content of 60%. Nectar secretion is limited to daytime hours, with peaks in the morning and afternoon, and then the plant reabsorbs the nectar at night to prevent it from being stolen. This can be considered a highly sophisticated adaptation of the Japanese knotweed to Japanese honeybees.

In other words, other insects are simply stealing the nectar for free (nectar robbing), and the bush vine gains nothing from them; these insects are merely there by chance.

Furthermore, although there is no published paper on the matter of wild grapes, according to Mr. Kakutani, who conducted research on this Japanese knotweed, the diurnal pattern of nectar production matched the diurnal pattern of flower visits by a bee called the rainbow bee, which is thought to be an effective pollinator (Kakutani, 2001). It is currently unknown whether the rainbow bee is a common bee, but it is possible that a smaller type of bee than the one that visits Japanese knotweed visits the flowers of wild grapes.

Did the Japanese knotweed plant hire a hornet as a bodyguard?!

However, it may be very well known to people who are familiar with the Japanese knotweed that hornets and paper wasps frequently visit it.

The bees that usually visit flowers belong to a group called honeybees, which are relatively small and often non-carnivorous. Does this unusual phenomenon of carnivorous bees visiting truly have no significance for the Japanese knotweed?

Gifu University is conducting research on this matter. According to their research, the number of carnivorous wasps on Cayratia japonica increases in August and September, but the number of lepidopteran larvae tends to decrease during that period (Kawabe et al., 2015).

This could mean that the Japanese knotweed deliberately provides nectar from its flowers to wasps, regardless of pollination, in exchange for allowing the wasps to eat the caterpillars or hairy insects that feed on its leaves. This is a mutualistic relationship.

It is known that the larvae of moths such as the striped hawk moth, grape hawk moth, and small hawk moth can parasitize the Japanese bush vine (Cayratia japonica). The Japanese bush vine may be protecting itself from these moths.

This is still in the research stage, but if it is true, it could be very troublesome for humans. However, wouldn't understanding the situation from the perspective of the Japanese bush vine be important for coexistence?

Are the fruits similar to grapes? Are they edible?

Both species produce berries. Since they belong to the grape family, this should be easy to imagine.

The fruits of Cayratia japonica are spherical, rarely somewhat rounded, and ripen to a black color (Hayashi et al., 2013). However, while the diploid variety distributed west of the Kanto region readily bears fruit, the triploid variety distributed east of the Kinki region and more common in eastern Japan does not bear fruit. Therefore, opportunities to see Cayratia japonica fruits may be rare.

On the other hand, wild grapes can be commonly found, and their fruits are also spherical, but their color ranges from white to purple or bluish-green (Hayashi et al., 2013).

However, there are some unknowns regarding the color of wild grape fruit. There are two theories: one that these purple or bluish colors are caused by parasitic galls (insect galls) formed by the larvae of grape gall midges or grape wasps, and that there are hardly any normal fruits ; and another that it is a natural process of maturation.

Currently, no scientific research has been conducted, so it is unclear which is correct. However, according to someone who actually cut open the fruit and observed whether it contained larvae, there were cases where it was bluish but contained no larvae, and cases where it was white but contained larvae (Hirono, 2017).

Therefore, it seems difficult to distinguish between grape galls (Grape gall midge galls) and grape wasp galls by color alone. However, since galls are said to be irregularly distorted and noticeably enlarged, it seems necessary to carefully check for differences from the surrounding fruit, not just by color.

By the way, are these fruits edible? Since they belong to the grape family, you might be expecting them to be tasty.

According to someone who has actually eaten it, the wild grape (Cayratia japonica) has been described as having "a slightly sweet taste, but it's slimy and tastes like eating the unripe, green fruit of the wild grape (Vitis coignetiae)" (Waki, 2011).

Furthermore, many field guides state that wild grapes are unpalatable and inedible. However, it is unclear whether this assessment refers to galls caused by insects.

Even if it's not tasty to humans, it's a valuable food source for wild animals, and for the Japanese knotweed (Cayratia japonica), it's an important means of seed dispersal. What kinds of wild animals eat it?

The only record we could find of Cayratia japonica being eaten by birds was (Takatsuki, 2021).

On the other hand, there are records of wild grapes being eaten by birds (Takatsuki, 2021), but there are also records of mammals such as Asiatic black bears, martens, and raccoons eating the fruit (Koike and Masaki, 2008). Surprisingly, it may be a fruit that appeals to both mammals and birds. It's strange that a fruit that should taste bad to humans is so popular.

It's still unclear whether the Japanese knotweed (Cayratia japonica) truly targets only birds, but how the differences in color and taste between the two species are perceived by wild mammals and birds remains an intriguing mystery.

References

Fukuhara, Tatsuhito. 2014. Huh? It's different from yesterday! Sex change in flowers. Nature Conservation 542: 22-23. ISSN: 0386-4138, https://what-we-do.nacsj.or.jp/2014/10/1290/

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

Hirono, Ikuo. 2017. Are the diverse colors of wild grape fruits due to galls? What color are normal fruits, anyway? Continued: A Walk Through the Trees 229. Tree Notebook. https://kinomemocho.com/sanpo_nobudo.html

Kakutani, Takehiko. 1992. Nectar secretion of Cayratia japonica and flower-visiting behavior of honeybees. Honeybee Science 13: 27-34. ISSN: 0388-2217

Kakutani, Takehiko. 1994. Pollination ecological studies on pollinating insect communities: Community composition viewed from nectar secretion patterns and interinsect competition. [Doctoral dissertation, Kyoto University]. https://doi.org/10.11501/3096539

Kakutani, Takehiko. 2001. Kakutani Home. https://www.museum.kyoto-u.ac.jp/english/staff/kakutani/kakutanij.html

Kakutani, T., Inoue, T., & Kato, M. 1989. Nectar secretion pattern of the dish-shaped flower, Cayratia japonica (Vitaceae), and nectar utilization patterns by insect visitors. Population Ecology 31(2): 381-400. ISSN: 1438-3896, https://doi.org/10.1007/BF02513213

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

Honami Kawabe, Yukiko Furukawa, Nobumitsu Kawakubo, and Koji Tsuchida. 2015. Diversity of insects that nectar-feed on Cayratia japonica: Ecological functions of wasp visits revealed. Abstracts of the Annual Meeting of the Ecological Society of Japan 62: PA1-149. https://www.esj.ne.jp/meeting/abst/62/PA1-149.html

Koike, Shinsuke & Masaki, Takashi. 2008. A literature review of woody plant fruit utilization by three species of carnivorous plants south of Honshu. Journal of the Japanese Forestry Society 90(1): 26-35. ISSN: 1349-8509, https://doi.org/10.4005/jjfs.90.26

Takatsuki, Seiki. 2021. Seed dispersal by birds to persimmon trees on the Azabu University campus. Azabu University Journal 32: 1-9. ISSN: 1346-5880, https://az.repo.nii.ac.jp/records/5404

Waki here. October 19, 2011. Wild Cayratia japonica berries (Vitaceae family). What kind of place is Etajima? http://wakiwakidonn.blog97.fc2.com/blog-entry-2781.html

Source

This article is a significantly expanded version of the one included in the following book.