Houttuynia cordata and Saururus chinensis both belong to the Saururus family and are perennial herbs that prefer humid conditions. Houttuynia cordata, in particular, is commonly consumed as "Houttuynia cordata tea" and is often seen growing in clusters along roadsides even in urban areas. People who have never seen them before may not know how to distinguish between them. Distinguishing between these two species is easy, as there are significant differences in both the inflorescence and the leaves. Houttuynia cordata is also similar to a plant with a very similar name, Polygonum cuspidatum, which belongs to the Polygonaceae family. While its leaves are quite similar to Houttuynia cordata, there are differences upon closer inspection, and its flowers and fruits are completely different. This article will explain the classification and morphology of the Saururus family.

What are Houttuynia cordata and Hangesho?

Houttuynia cordata, also known as dokudami, is a perennial herb distributed in Honshu, Shikoku, Kyushu, and the Ryukyu Islands of Japan; as well as in China, the Himalayas, and Southeast Asia, growing in shady areas and wetlands in mountainous regions.

Hangesho (Saururus chinensis), also known as Katashirogusa, is a perennial herb distributed in Honshu, Shikoku, Kyushu, and the Ryukyu Islands of Japan; as well as in Korea, China, and Southeast Asia, growing in damp places such as swamps and wetlands.

Both belong to the Saururaceae family and are perennial plants that prefer damp conditions. Saururaceae, in particular, is commonly consumed as "salvia tea" and can often be seen growing in clusters along roadsides even in urban areas. However, it emits a distinctive odor when stepped on, which some people may find unpleasant.

[Seed Plant Encyclopedia #024] What are the species of the Saururaceae family? Photo list

The Saururaceae family consists of perennial herbs with a generally pungent odor. Their leaves are simple and have stipules. The flowers are small, borne in dense spikes, and lack a perianth. The fruit is a capsule or berry, and the seeds are spherical with a high endosperm content. There are 4 genera and 6 species found in North America and Asia...

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Some people might be wondering about the differences between these two types.

What is the difference between Houttuynia cordata and Saururus chinensis?

Although Houttuynia cordata and Saururus chinensis belong to the same family, they look quite different and are easy to distinguish (Kanagawa Prefecture Flora Survey Association, 2018). This can be expected from the fact that Houttuynia cordata belongs to the genus Houttuynia, while Saururus chinensis belongs to the genus Saururus.

The first difference that can be mentioned is that Houttuynia cordata has 4 to 6 white bracts at the base of the inflorescence, while Saururus chinensis does not have any bracts at the base of the inflorescence.

The white parts of the Houttuynia cordata plant are often mistaken for "petals," but these are not petals but rather structures called "involucral bracts," which are modified leaves.

Instead, during its flowering season, a portion of the upper surface of the leaves of Hangesho (Saururus chinensis) turns white. This is not the case with Houttuynia cordata (Houttuynia thunbergii). This is the origin of the Japanese names "Hangesho" (half-makeup) and "Katajirogusa" (one-sided white grass).

Another difference is that the inflorescence of Houttuynia cordata is only 1-3 cm long, while that of Saururus chinensis is 10-15 cm long.

Therefore, you might get the impression that Hangesho is larger.

In the case of Houttuynia cordata, the part surrounded by white bracts is the "inflorescence." If you look closely, you will be able to see that there are many flowers with stamens and pistils inside the inflorescence.

As you can see in the photos, the leaves are also completely different in size, with the leaves of Hangesho being longer than those of Dokudami.

What is the difference between Houttuynia cordata and Polygonum multiflorum?

Fallopia multiflora is native to eastern China, Taiwan, Vietnam, and Thailand. It is said to have been imported to Japan for medicinal purposes and is now found growing wild in mountainous areas and along roadsides throughout the country.

Houttuynia cordata is a plant with a similar name to Houttuynia cordata, and as its name suggests, its heart-shaped leaves with palmate veins are very similar to those of Houttuynia cordata, so some people may have trouble distinguishing them.

However, they are completely different in terms of classification. As mentioned above, Houttuynia cordata belongs to the Polygonaceae family, while Polygonum multiflorum belongs to the Polygonaceae family.

Regarding the leaves, there is a difference in that the rounded upper part (ear-like projection) of the heart shape protrudes only slightly in Houttuynia cordata, but it protrudes considerably longer in Polygonum multiflorum.

The flowers are completely different; Houttuynia cordata produces a dense inflorescence called a "flower spike," while Polygonum multiflorum produces a panicle inflorescence. Of course, Polygonum multiflorum does not have the white bracts that are present in Houttuynia cordata.

The fruits are also completely different. Houttuynia cordata has a capsule that is green and almost spherical, while Polygonum multiflorum has an achene with a thin part called a "wing" that catches the wind.

Are there any other similar species?

There are no other species of Houttuynia cordata in Japan, but several varieties are known. *Houttuynia viridis * (green Houttuynia) is a variety with some green bracts. *Houttuynia plena* (double-flowered Houttuynia) is a variety with double bracts. *Houttuynia 'Variegata' (variegated Houttuynia) is a variety with variegated leaves.

A related species, Saururus cernuus, is known to exist in the Americas. The upper surface of the leaves of Saururus cernuus does not turn white even during the flowering season. It is sometimes planted in aquariums and biotopes in Japan.

References

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

Both Polygonum capitatum and Polygonum persica belong to the genus Polygonum in the family Polygonaceae. They are among the most common perennial herbs in the genus Polygonum, and Polygonum persica in particular can be commonly observed on the stone walls of houses in urban areas. The genus Polygonum is a vast group of species, but these two species share many morphological similarities, such as their vine-like stems, capitate inflorescences, and ovate leaves, which can make them difficult to distinguish . However, they can be easily distinguished by checking the color of the flowers and the hairiness of the leaves. This article will explain the classification of Polygonum capitatum and Polygonum persica.

What are Polygonum capitatum and Polygonum capitatum?

Persicaria chinensis, also known as climbing buckwheat, is a perennial herb that grows on warm coastal areas and is distributed in Honshu (south of the Kanto region), Shikoku, and Kyushu in Japan; as well as in China, Korea, Southeast Asia, and South Asia (Kanagawa Prefecture Flora Survey Association, 2018; RBG Kew, 2023).

Persicaria capitata, also known as Polygonum, is a perennial plant native to Southeast and South Asia. Cultivated as an ornamental plant, it has naturalized and is found growing on stone walls and other structures along coastlines throughout the world, including Japan.

Both belong to the genus Persicaria in the family Polygonaceae, and are among the most common perennial herbs in the genus Persicaria. In particular, Polygonum capitatum can be found very commonly on the stone walls of houses in urban areas. Their distinctive features include creeping stems and capitate (round cluster) inflorescences, which give them a charming appearance and are likely the reason for their popularity.

Like other plants in the Polygonaceae family, it has flowers composed of perianth segments that are indistinguishable from petals and sepals.

Furthermore, while the genus Polygonum longisetum includes a vast number of species, these two species share many morphological similarities. They are identical in that the pistil's style falls off after flowering, the inflorescence is capitate, the leaves are ovate, the stem lacks backward-pointing thorns, the petiole lacks wings, and the underside of the leaves lacks glandular dots.

Therefore, some people might confuse them, especially since their names are similar.

What is the difference between Polygonum capitatum and Polygonum capitatum?

However, distinguishing between these two types is not difficult. The easiest way to tell them apart is by the color of the flower.

Specifically, while Polygonum capitatum usually has white flowers, Polygonum capitatum has pale pink to white flowers.

While this method alone is sufficient for distinguishing them, these two species have other clear differences besides just being different in color.

Regarding the leaves, there is a difference in that Polygonum capitatum has hairless leaves on both sides, while Polygonum capitatum has short hairs on both sides.

Regarding the stems, Polygonum capitatum creeps along the ground and grows to over 2 meters in length, while Polygonum capitatum grows to a maximum length of about 50 cm.

Comparing these should prevent any mistakes.

In terms of habitat, Polygonum capitatum is frequently found even in urban areas on Honshu, while Polygonum cuspidatum is only occasionally seen on coastlines.

However, when I visited Yakushima, I was able to frequently observe Polygonum cuspidatum even in urban areas, suggesting that it may indeed be better suited to breeding in southern regions.

In Malaysia, the flowers of Polygonum cuspidatum are known to be visited by various insect species, including honeybees (Apis), hoverflies (Eristalis), blowflies (Lucilia), and potter wasps (Eumedes) (Wong et al., 2015).

References

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

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/

Wong, MM, Lim, CL, & Wilson, JJ 2015. DNA barcoding implicates 23 species and four orders as potential pollinators of Chinese knotweed (Persicaria chinensis) in Peninsular Malaysia. Bulletin of Entomological Research 105(4): 515-520. https://doi.org/10.1017/S0007485315000358

Agrimonia pilosa, Agrimonia fusiforme, and Agrimonia pilosa are all perennial herbs belonging to the genus Agrimonia in the family Rosaceae, and in Japan they grow in forest edges and other similar areas. Their most distinctive features are the hook-shaped thorns below the calyx and their fruits, which are "burrs." As their names suggest, these two species differ in their overall size. Specifically, the shape of the leaflets and the number of stamens are important differences. There is also a plant called Mizuhiki, which has a very similar name, but it belongs to the Polygonaceae family and, although its fruits are also "burrs," the shape of its leaves, flowers, and fruits are all different. This article will explain the classification of the genus Agrimonia.

What are Kinmizuhiki and Himekinmizuhiki?

Agrimonia pilosa var. japonica, also known as golden water lily, is a perennial herb commonly found in Hokkaido, Honshu, Shikoku, and Kyushu in Japan; as well as in Korea, China, Sakhalin, Ussuri, and Indochina, growing along roadsides, forest edges, and grasslands in lowlands and mountainous areas (Kanagawa Prefecture Flora Survey Association, 2018).

Agrimonia nipponica, also known as Himekinmizuhiki, is a perennial herb distributed in Hokkaido (southwestern part), Honshu, Shikoku, and Kyushu in Japan, as well as in Korea (Jeju Island). It grows in woodlands, forest edges, and roadsides in lowlands to mountainous areas. It tends to prefer shade more than Agrimonia pilosa.

Both belong to the genus Agrimonia in the family Rosaceae and are perennial herbs that grow in forest edges and other similar areas in Japan. Morphologically, they share common characteristics such as odd-pinnately compound leaves, five-petaled flowers with yellow petals, and inflorescences that are sparsely arranged spike-like inflorescences.

The most significant common features are the hook-shaped thorns beneath the calyx and the fact that their fruits are "burrs" that stick to things.

These distinctions can be difficult to make without careful observation.

What is the difference between *Persicaria filiformis* and *Persicaria thunbergii*?

The main difference between *Persicaria filiformis* and *Persicaria thunbergii* is, as the names suggest, their overall size.

The main difference between Agrimonia pilosa and Agrimonia ovalifolia lies in their odd-pinnately compound leaves. The odd-pinnately compound leaves of the Agrimonia genus contain a mixture of larger and smaller leaflets.

In Agrimonia pilosa, the number of larger leaflets is usually 5 to 9, and the tip usually gradually narrows to an acute point, whereas in Agrimonia pilosa, the number of larger leaflets is usually 3 to 5, and the tip usually narrows abruptly to a rounded or slightly pointed point.

There are also differences in the flowers themselves.

While *Persicaria filiformis* has 8 to 15 stamens and oval-shaped petals, *Persicaria thunbergii* has 5 to 6 stamens and narrower petals.

Note that *Persicaria filiformis* var. nepalensis is sometimes classified based on the amount of hair. *Persicaria filiformis* var. viscidula is sometimes called *Persicaria filiformis* var. viscidula, which has semi-circular stipules at the base of the leaves with many serrations and dense yellowish-brown hairs on the stem. *Persicaria filiformis* var. viscidula f. subglabra has fewer hairs. *Persicaria filiformis* var. succapitata has inflorescences and fruit clusters that do not form spikes but rather clump together like a "Daruma" doll, with round leaflets and coarse serrations (Naruhashi & Seo, 1996).

Additionally, a hybrid of two species, Agrimonia x nippono-pilosa, is known. Its leaf shape is similar to that of Agrimonia pilosa, but its serrations resemble those of Agrimonia pilosa var. japonica, the glandular dots on the underside of the leaves are unclear, and all of its fruits are sterile.

What are other species in the genus Agrimonia?

Although the population of the genus Agrimonia is quite small, several other species are known.

Agrimonia coreana is distributed in Hokkaido (southwestern part), Honshu, Shikoku, and Kyushu in Japan; as well as in Korea, China (northeastern part), and Siberia (southeastern part).

Agrimonia noguchii subsp. hakonensis is distributed in at least Kanagawa and Shizuoka prefectures.

In *Persicaria filiformis*, the stipules are small and clasp the stem, the flowers are about 6 mm in diameter, the petals are oblong and narrow, there are 5 to 8 stamens, the mature fruit is about 3 mm in diameter, and the leaves are often clustered at the base of the stem. In contrast, these two species have large stipules that spread out in a fan shape and clasp the stem, the flowers are 7 to 15 mm in diameter, the petals are oval, there are 10 to 28 stamens, the mature fruit is about 5 mm in diameter, and the leaves are often evenly spaced on the stem.

For a distinction between the two species, please refer to the Kanagawa Prefectural Flora Survey Association (2018).

What is the difference between Kinmizuhiki and Mizuhiki?

There is a plant called Mizuhiki that has a similar name to Kinmizuhiki.

Persicaria filiformis, also known as Mizuhiki, is a perennial herb distributed in Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea, China, India, and the Himalayas, and can be found in forest edges everywhere.

However, while golden mizuhiki belongs to the rose family, mizuhiki belongs to the buckwheat family. They are completely different species, differing only in their similar names and the fact that their fruits are similar in that they stick to things.

In Polygonum filiforme, the leaves are entire, and the flowers consist only of sepals, which are four-lobed. The lobes are oval-shaped, with the upper ones being red and the lower ones being lighter in color. The fruit retains its curved style, which causes it to stick to surfaces.

References

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

Naruhashi, Naohiro & Seo, Mutsu. 1996. A new variety of the genus Agrimonia in the Rosaceae family: Agrimonia spp. 'Daruma-kinmizuhiki'. *Phytogeography and Taxonomy* 44(1-2): 82-84. https://doi.org/10.24517/00055582

Rumex japonicus, Rumex longifolius, Rumex crispus, and Rumex serrata all belong to the genus Rumex in the family Polygonaceae. Originally, only Rumex japonicus was distributed in Japan, but multiple species have invaded and become extremely common weeds. They all share a preference for disturbed ground, and are often found growing together. Furthermore, the appearance of their flowers and fruits is very similar, making identification difficult without careful comparison. They can be distinguished from sorrel species by the shape of their leaves and flowers. More than 10 species of Rumex have been confirmed in Japan, and accurate identification requires a field guide, but if we limit ourselves to the four most common species, the most accurate method of identification is by the shape of the "inner perianth that encloses the fruit." The flowers are very inconspicuous and small, with no distinction between the inner perianth (petals) and outer perianth (sepals). This is because they are wind-pollinated, not pollinated by insects. After pollination, the inner perianth remains, swells and flattens, and encloses the fruit (achene). This structure allows the seeds to be carried to other locations by wind and water. However, the presence of thorns (serrations) on the inner perianth and "white, knob-like protrusions" suggests the possibility of "dispersion by attachment to animals" or "dispersion by animal feeding," although this has not been adequately researched. This article will explain the classification, pollination ecology, and seed dispersal of dock species.

What are Rumex japonicus, Rumex longifolius, Rumex crispus, and Rumex serrulata?

Rumex japonicus, also known as dock (or pygmy dock), is a common perennial herb found in Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea and China, growing in wastelands, roadsides, and fields in urban areas and around human settlements.

Rumex crispus, also known as long-leaved dock, is native to Europe and has naturalized widely throughout the Eurasian continent. It is a perennial herb that grows in wastelands and roadsides in urban areas and around human settlements.

Rumex conglomeratus, also known as "wasteland dock," is native to Europe and has naturalized widely throughout Eurasia. In Japan, it was introduced during the Meiji era and is commonly found in central Honshu, growing in wastelands and roadsides in urban areas and around human settlements.

Rumex obtusifolius, also known as Ezo dock, is native to Europe and has naturalized widely throughout the world, including Japan. It is a perennial herb that grows in wastelands and roadsides in urban areas and around human settlements.

All of these species belong to the genus Rumex in the family Polygonaceae. Originally, only Rumex japonicus was found in Japan, but now several species have invaded from Eurasia and have become extremely common weeds. They also share a preference for disturbed soil, and are often found growing together. Furthermore, their flowers and fruits look very similar. Therefore, they may be easily confused if not carefully observed.

What is the difference between dock and sorrel?

Before considering these four species, it's important to note that the genus Rumex also includes other species besides the common dock (Rumex acetosa) and the dwarf sorrel (Rumex acetosella). What are the differences between these two species?

First, there is a difference between dock species (Rumex serrata) and sorrel species (Rumex acetosa). In other words, all dock species have "hermaphrodite flowers" that have both stamens and pistils, but sorrel species have two types: individuals with "male flowers" that have only stamens (male plants) and individuals with "female flowers" that have only pistils (female plants).

The female flowers of this sorrel species are very red and conspicuous, so you can spot the red inflorescence of sorrel species even from a distance. This is not the case with dock species.

In terms of leaf morphology, dock species have wedge-shaped, rounded, or heart-shaped leaf bases, while sorrel species have scaly or lanceolate leaf bases. This difference may be useful when observing plants outside of their flowering season.

In addition, the Japanese name for sorrel (suiba) is said to be "suiba" (sour leaf), derived from its sour taste. This sourness comes from oxalic acid, which is also found in dock plants, but sorrel seems to be more sour, possibly because it contains more oxalic acid. According to someone who actually compared the two, "suiba is clearly more sour" (Ayumin, 2021). Therefore, this can be used to distinguish them, but it seems that no one has confirmed whether all dock plants are not sour.

What are the differences between *Rumex japonicus*, *Rumex longifolius*, *Rumex serrata*, and *Rumex japonica*?

More than 10 species of the genus Rumex have been identified in Japan, including the sorrel species mentioned earlier, making accurate identification difficult without consulting a field guide. However, the four species listed at the beginning are the most commonly found in urban areas and are frequently encountered. Therefore, this section will explain how to distinguish between these four species. For those who want to accurately distinguish all species, please refer to Ohashi et al. (2017) or the Kanagawa Prefectural Flora Survey Association (2018).

Firstly, in Rumex japonicus, the edges of the inner perianth surrounding the fruit have prominent thorns, whereas in Rumex crispus, Rumex longifolius, and Rumex serrata, the edges of the inner perianth surrounding the fruit are entire or have only shallow serrations.

The "inner perianth surrounding the fruit" is a structure unique to the Rumex genus. It is the inner perianth that was present between the flowers, which remains after flowering and becomes thinner, with a white, knob-like projection attached to the center. This is quite noticeable even from a distance.

Regarding the remaining three species, in *Rumex crispus*, the flowers and fruits are spaced apart and arranged in whorls, so the inflorescence appears sparse, and the inflorescence and fruit clusters have bracts. In contrast, in *Rumex rotundifolia* and *Rumex longifolia*, although the flowers and fruits are also arranged in whorls, they are spaced closely together, forming a large panicle inflorescence overall, and the inflorescence and fruit clusters lack bracts.

Regarding dock (Rumex japonicus) and long-leaved dock (Rumex crispus), the difference is that in dock, the inner perianth surrounding the fruit has low serrations along the edge and a slightly pointed tip, while in long-leaved dock, the inner perianth has an entire margin with a rounded tip.

In addition, it may be possible to distinguish them based on the leaves alone, but this would be complicated due to differences between stem leaves and basal leaves, so we will omit that here. The period when the inner perianth is present is limited, but it would be desirable to confirm this point if possible.

Furthermore, these four species prefer similar environments and coexist, leading to the observation of many hybrids. If fruiting is infrequent and intermediate characteristics are present, it may be necessary to consider the possibility of a hybrid.

What is the structure of a flower?

The flowers of the Rumex genus have a similar structure to typical flowers. However, they are very inconspicuous and small, and the calyx and petals are almost indistinguishable in appearance. For this reason, the part corresponding to the calyx is often called the "outer perianth," and the part corresponding to the petals is called the "inner perianth."

Dock (Rumex rotundifolia) flowers from June to August (Wu et al., 2003). Its inflorescence is a panicle, densely arranged in multiple whorls. It is monoecious, with both hermaphroditic and female flowers. The pedicels are slender, with nodes located below the middle and clearly defined. Each flower consists of three outer perianth segments, three inner perianth segments, six stamens, and one pistil.

Rumex rotundifolia flowers from June to August, with flowers borne in long racemes that are densely arranged in multiple whorls. It is monoecious, with both hermaphroditic and female flowers. Each flower consists of three outer perianth segments, three inner perianth segments, six stamens, and one pistil. The pistil has three styles, and the stigma is finely divided.

Rumex crispus flowers from June to July. Its flower stalks are branched with long internodes, and the flowers are densely arranged in whorls at each node. The pedicels are 1-4 (up to 5) mm long. The flowers are small, with the inner perianth measuring 2-3 mm in length and 1-1.6 (up to 2) mm in width.

Rumex japonicus flowers from June to August. The flowers are borne in long racemes, arranged in whorls with spacing between tiers. It is monoecious, with both hermaphroditic and female flowers. Each flower consists of 6 perianth segments (sepals), 6 stamens, and 1 pistil.

How is pollination done?

It is known that flowers of the Rumex genus, including sorrel species, are commonly pollinated by wind (Wagatsuma et al., 1974; Zaller, 2004; CABI, 2021). In fact, airborne pollen has been discovered in Japanese research. Morphologically, the indistinguishable nature of the sepals and petals indicates a lack of appeal to insects, and the absence of nectar secretion suggests that there is no need to attract insects.

Among wind-pollinated flowers, it is classified as a "pendulous type," and because the flower stalks extend downwards, the flowers appear to droop and are easily swayed by the wind (Utsumi, 2002).

What is the structure of the fruit?

The fruits of the Rumex genus are all achenes. An achene is a fruit with a hard, membranous pericarp that dries when ripe and contains one seed in each chamber. However, as mentioned above, the three inner perianth segments enlarge during fruiting and enclose the fruit, so the shape of the fruit cannot be seen from the outside (Iwase et al., 2021). In addition, some species have "white, knob-like projections (tubercles)" on the inner perianth segments, which is also a distinctive feature, but some species, such as Rumex acetosa and Rumex chinensis, do not have these. Only one fruit (achene) is enclosed within the three inner perianth segments.

The three inner perianth segments of the dock are broadly heart-shaped, 4-5 mm long and 5-6 mm wide. All inner perianth segments have white, knob-like projections, distinct reticulate venation, a heart-shaped base, irregularly toothed margins, and an acute apex, with the teeth measuring 0.3-0.5 mm in height. The inner achenes are dark brown, glossy, broadly ovate, sharply triangular, about 2.5 mm long, with a narrow base and an acute apex.

The three inner perianth segments of *Rumex japonicus* are broadly ovate, entire, with rounded tips and a knob-like projection in the center. The size of the knob-like projection varies. The inside of the inner perianth is slightly concave, but otherwise almost flat. The achene is three-angled and brownish-red.

The three inner perianth segments of *Rumex crispus* are oblong-ovate, entire, and the central knob-like projection is often reddish. The achenes are the smallest among the *Rumex* species, measuring 1.5–2 mm in length and 1–1.6 (2) mm in width, and are dark brown.

The three inner perianth segments of *Rumex japonicus* are ovate, with a slightly elongated, pointed tip, long projections along the edges, and a knob-like projection in the center. The projections along the edges are often sparse, and the knob-like projection is usually red. The achenes are 2–2.7 mm long and 1.2–1.7 mm wide, triangular in shape, and brown to reddish-brown in color.

What are the methods for seed dispersal? There are many methods besides "wind dispersal"!

The most common seed dispersal method for the Rumex genus is wind dispersal (CABI, 2021). The three flattened inner perianth segments are carried away by the wind, spreading to various locations. This is the same method used for pollen dispersal, and by not relying on luck factors like insects or animals, it can spread very effectively in open, disturbed areas. The flattened structure is also well-suited to floating on water, so water dispersal also occurs.

However, the presence of various appendages suggests that dispersal is not simply wind-based. For example, in some species, including Rumex japonicus, the inner perianth segments have serrations. This is thought to allow them to adhere to the fur and feathers of animals (mammals and birds), including humans, enabling them to travel long distances (CABI, 2021). In other words, they act as "burrs" and disperse by attaching to animals. However, the specific animals involved are unclear. Their shape makes it seem unlikely they would adhere to human clothing.

In addition, while many species exhibit "white, knob-like protrusions" on the inner perianth segments, some species lack them. What role do these protrusions play? It seems that lighter protrusions would be preferable if they were to be carried by wind or water.

I couldn't find any proper research on this. I think there are several different ideas about this role.

Firstly, after being carried away by wind and water, seeds accumulate in the soil, but this is not always a suitable environment for their survival. Therefore, it is already known that they wait underground until they are ready to germinate, forming a "seed bank" (CABI, 2021). In one study, 83% of Rumex japonicus seeds remained viable after being buried for 21 years.

Therefore, it may exist to supply nutrients to the seeds while it is in existence as a seed bank. However, structurally, the protrusions do not appear to be in contact with the seeds, so it is unclear whether this is possible, and it is questionable whether dormancy is impossible without such a structure.

Secondly, it may serve the purpose of providing nutrients to animals that eat the seeds. In fact, it is known that the seeds are eaten by mammals such as birds and cows (CABI, 2021; Bhandari & Park, 2022). This is called "animal dispersal." In the case of birds, it is said that they will eat the fruits of the dock family if there are no other good food sources. It is also known that the ingested seeds are difficult to digest and can be dispersed through feces. Based on this fact, it is natural to think that there is something about the fruit that makes animals think, "It's delicious!"

The third reason is that it's a structure for buoyancy. The cross-section of the white, knob-like protrusions looks like cork. Perhaps having such a structure actually makes the seeds float more easily.

It is thought that one or more of these roles exist, but this has not been verified at all. They may have a great many seed dispersal methods, but which one they primarily rely on likely varies depending on the species.

References

Ayumin. [Ayumin's Weed Cafe]. (January 20, 2021). Thorough Comparison! Sorrel vs. Dock ① ~Comparing raw and boiled versions by color~ [Video]. YouTube. https://www.youtube.com/watch?v=cTcnUJvmrkQ

Bhandari, GS, & Park, CW (2022). Molecular evidence for natural hybridization between Rumex crispus and R. obtusifolius (Polygonaceae) in Korea. Scientific Reports, 12 (1), 5423. https://doi.org/10.1038/s41598-022-09292-9

CABI. (2021). Rumex obtusifolius (broad-leaved dock). CABI Compendium. https://doi.org/10.1079/cabicompendium.48064

Iwase, T., Kawana, K., & Iijima, K. (2021). Weeds in schoolyards (revised edition). National Rural Education Association. ISBN: 9784881371992

Kanagawa Prefecture Flora Survey Association. (2018). Kanagawa Prefecture Flora 2018 Electronic Edition. Kanagawa Prefecture Flora Survey Association. ISBN: 9784991053726

Ohashi, Hiroyoshi; Kadota, Yuichi; Murata, Hitoshi; Yonekura, Koji; and Kihara, Hiroshi. (2017). Wild Plants of Japan (Revised New Edition, Vol. 4: Malvaceae to Apocynaceae). Heibonsha. ISBN: 9784582535341

Utsumi, Shusaku. (2002). Why are flowers beautiful? 1. Insects and pollination. Research Bulletin of the Faculty of Education, Chiba University, 50, 441-448. ISSN: 1348-2084, https://opac.ll.chiba-u.jp/da/curator/900026751/

Yoshinori Wagatsuma, Ryuji Matsuyama, Mikiya Sato, Koji Ito, Tamiko Mizutani, and Yoko Fujisaki. (1974). Rumex acetosa and dock pollen allergy (hay fever). Allergy, 23(3), 245-246. https://doi.org/10.15036/arerugi.23.245_2

Wu, ZY, Raven, PH, & Hong, DY (Eds.). (2003). Flora of China (Vol. 5 Ulmaceae through Basellaceae). Science Press, and Missouri Botanical Garden Press. ISBN: 9781935641056

Zaller, JG (2004). Ecology and non-chemical control of Rumex crispus and R. obtusifolius (Polygonaceae): a review. Weed Research, 44 (6), 414-432. https://doi.org/10.1111/j.1365-3180.2004.00416.x

Buckwheat, Tartary buckwheat, and Japanese buckwheat are all species that can be found in Japan, either cultivated or naturalized. Buckwheat, in particular, is indispensable to Japanese people as a noodle dish, but few people can distinguish between these three species as plants. These three species can be distinguished by the way their flowers grow, the shape of their fruits, and the shape of their leaves. Buckwheat is thought to have evolved in the mountainous regions of China, which explains many of its characteristics. It is nutritious and eaten all over the world, and although it is not clear how Japanese people started eating it as noodles, it is thought to be a result of the overlap between the noodle-eating culture that came from China and the sword-making culture. It is generally thought that honeybees visit the flowers, but other insects are also important in its native habitat, and the presence of various insects in Japan increases the fruiting rate. The fruit as a plant does not receive much attention, but it is classified as an achene, and the prominent three ridges are thought to have developed for wind dispersal. This article will explain the classification, origin, history, and pollination ecology of buckwheat.

Pseudocereals native to China

Buckwheat (Fagopyrum esculentum) is native to China and is widely cultivated in the Northern Hemisphere, from Eastern Europe to Japan and the Americas, as an annual plant grown as a necessity or cash crop (Gondola & Papp, 2010). It is a temperate plant that has been used as a source of nutrition for humankind since prehistoric times. It belongs to the Polygonaceae family. It is not a grain in the strict sense as it is not a grass, but it is sometimes called a "pseudocereal" because it is used in the same way as grains.

Temperate or subtropical climates are most suitable, provided rainfall is stable during the growing season. It also thrives in poor soil, growing well even in areas where many other important grains fail. Furthermore, its resistance to diseases and pests, short growing season, and low maintenance requirements contribute to its popularity. It's an essential part of the Japanese diet, commonly consumed as an ingredient in noodles.

Tartary buckwheat (Fagopyrum tataricum) is relatively frost-tolerant and is most widely cultivated in the Himalayan regions of India, Nepal, and Bhutan, as well as in southern China, especially at altitudes above 2000m. It is a diploid plant that self-pollinates, and its flowers are pollinated before they open (cleistogamous pollination). In Japan, it attracted attention for its high rutin content, which is believed to be effective as a vascular strengthening agent, and was introduced in 1985. Since then, the consumption of tartary buckwheat tea and other products has increased. It is also sometimes used to make noodles.

Fagopyrum dibotrys, also known as Shakuchiri buckwheat, is native to northern India and, like Tartary buckwheat, was cultivated in fields in Japan as a source of rutin. However, its seeds have a strong bitter taste and cannot be eaten like other buckwheat varieties. Currently, it is mostly found growing wild in clusters.

Both belong to the buckwheat genus of the Polygonaceae family, and their flowers and fruits are very similar. While their names are often heard in reference to food, few people may be able to distinguish between them as plants.

What are the differences between buckwheat, Dattan buckwheat, and Shakuchiri buckwheat?

However, the three species of buckwheat found in Japan are distinguished as follows (Kanagawa Prefecture Flora Survey Association, 2018).

First, in Tartary buckwheat, the flowers are few in number and grow in the leaf axils, and the fruit has blunt ridges, whereas in the other two buckwheat species and Chrysopogon spp., the flowers grow in racemes, and the fruit has sharp ridges.

The reason there are few buckwheat flowers is that buckwheat primarily relies on self-pollination.

Also, the term "ridges" on a fruit might be a little difficult to understand, but think of them as the flat, pointed parts of the fruit. In Tartary buckwheat, these ridges are relatively rounded, but in buckwheat and Japanese buckwheat, the flat parts are clearly visible.

The main difference between buckwheat and shakuchiri buckwheat is that buckwheat is a perennial plant with a tuberous rhizome and triangular leaves, while shakuchiri buckwheat is an annual plant with thin, hair-like roots and irregularly shaped pentagonal leaves.

The origin of buckwheat: Why is buckwheat rich in polyphenols?

Based on the diversity of closely related species, buckwheat is believed to originate from the eastern side of the Himalayas and the mountainous regions of Yunnan Province and the area between Yunnan and Sichuan Provinces in southwestern China (Gondola & Papp, 2010).

This location receives plenty of sunlight and is a dry to semi-arid plateau or mountain range highland at an altitude of 2000 to 3500 meters.

The mountainous regions at altitudes of 2000 to 3500 meters have a vastly different environment from the lowlands, with low temperatures and atmospheric pressure, and high levels of ultraviolet stress. Furthermore, low temperatures hinder the function of reactive oxygen species scavenging enzymes, making survival even more challenging (Inoue, 2019).

Buckwheat contains pigments such as polyphenols that make it less susceptible to oxidative damage that occurs during photosynthesis, even at low temperatures. Rutin is a prime example of this.

Polyphenols offer three benefits in one: they absorb ultraviolet rays, providing a sunshade-like effect, and they also offer resistance to insects.

Buckwheat contains polyphenols, which have antioxidant properties for humans and give it a "healthy" image. However, buckwheat was originally used to protect itself from the natural environment.

How did the cultivation of plants in ancient China and their subsequent spread to the world occur?

According to archaeological and historical documents, buckwheat was widely cultivated and used as a staple food in ancient China from the 5th to 3rd centuries BC (Gondola & Papp, 2010). It was highly valued as a crop that could overcome famine and disaster.

Buckwheat cultivation has been practiced in Japan since the Jomon period (1000 BC), in northern China since several hundred years BC, and in eastern Tibet for over 2000 years.

Surprisingly, it is believed that it spread to Europe shortly after its introduction from its place of origin to northern China (2nd-1st century BC). However, large-scale cultivation did not begin until the 15th century.

In other regions as well, it gradually spread to various parts of the world: Southeast Asia, India, and Asia Minor in the 8th century; Siberia and Russia in the 13th century; the Americas in the 17th century; and subsequently Africa. It is believed that the main part of this spread occurred via the Silk Road, a trade route that flourished between the 2nd century BC and the 18th century.

In particular, the "Southern Silk Road," known in China as the "Tea Horse Road," is thought to have played a crucial role in the spread of buckwheat (Inoue, 2019). Here, Yunnan and the Tibetan people traded. Yunnan needed horses for war, and the Tibetan people needed tuochā (a type of dark tea) due to a shortage of vegetables. At this time, nutrient-rich buckwheat was highly valued as a portable food for travel along mountainous routes.

Buckwheat was originally eaten raw!?

Japanese people almost exclusively eat soba noodles. However, you rarely hear of this kind of culture in other countries, right? How was soba originally eaten?

In Nepal, near the plant's place of origin, the Rai people actually eat buckwheat berries raw (Inoue, 2019).

When Japanese researchers tasted it, they found it to have a dry, crumbly texture and a sweet, slightly bitter taste. However, the more you chew it, the more the starch is broken down by the amylase in saliva, making it sweeter and easier to eat.

Why did this way of eating become widespread? As mentioned above, it was used as a portable food during journeys along the southern Silk Road and mountainous terrain. Unlike other grains, buckwheat does not require processing to eat. This was likely a major factor in its importance. Furthermore, buckwheat is also important because it contains minerals, vitamins, protein, and polyphenols, making it nutritionally superior.

While the closely related buckwheat (Tartary buckwheat) has a strong bitter taste and is not popular with Japanese people, there is a theory that humans become less sensitive to bitterness when fatigued, so this may not have been a major disadvantage in mountainous regions where strenuous movement is required.

Incidentally, tea plants are also a preserved food that can be eaten as is, and they originate from a similar region to buckwheat, and they share the characteristic of being bitter, leading to the theory that they are connected through cultural spheres.

Why is black tea preferred over green tea in the UK? Are flies the only ones that visit tea plant flowers?

Tea plants contain essential nutrients like catechins and caffeine, making them an indispensable beverage in Japan, enjoyed both at home and on the go. As you may know, its origin lies in China, and it's a species not native to Japan. However, even in China, wild varieties haven't been confirmed, which is puzzling...

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What is the reason why Japanese people started eating soba noodles?

That makes me wonder, why did the Japanese start eating soba as noodles?

In Japan, buckwheat has been consumed as a food source since the Jomon period, when buckwheat was introduced from the continent (Inoue, 2019). Particularly due to the characteristics mentioned above, it was widely cultivated in mountainous areas, and "sobagaki," a mochi-like confection made by kneading buckwheat flour with hot water, was eaten until around the middle of the Edo period. Because buckwheat is a fruit of the Polygonaceae family, its interior is soft and threshing is impossible, so the only way to process it is to grind it into flour.

The earliest documented record of "soba-kiri," a type of noodle dish, is believed to be in "Dai Nihon Joho , Nihon Nihon Dōsha" (First Information on Japan, Second Draft), written in 1548 by Nicolao Lancilot, the head of St. Paul's Seminary of the Society of Jesus, who came to Japan as a missionary (Inoue (2019) spells it Lancilot, but this is thought to be a typographical error and has been corrected since Yamato (2014)). Lancilot was a person who gathered information on Japan at the request of Francis Xavier, and was, in a sense, Xavier's right-hand man.

The exact circumstances surrounding the creation of "soba-kiri" (cut soba noodles) are unknown, but it is thought that the culture of cut noodles was introduced from Tang China during this period, and that soba-kiri was an imitation of it. Furthermore, the development of knives for cutting soba noodles is related to the development of swords, and this too was likely a necessary condition for the development of soba-kiri.

It is believed that this type of soba noodle first developed in Nagano Prefecture in the 17th century, and records of lunch lots also date back to Nagano Prefecture. This is the origin of the current "Shinshu soba." As mentioned above, buckwheat is best suited to mountainous regions, so it makes perfect sense that it developed in Nagano Prefecture, where the Japanese Alps are located.

Soba noodles became widely popular in urban areas during the Edo period, serving as fast food for busy craftsmen working on wooden buildings. Their ability to be served quickly and eaten standing up made them very convenient as fast food at the time (Inoue, 2014). This is the origin of today's "standing soba" restaurants.

Buckwheat has evolved to use "light" to kill insects!?

Buckwheat leaves contain a substance called "phagopyrin." Herbivorous livestock that eat large quantities of the leaves will develop photosensitivity and dermatitis if exposed to ultraviolet rays (sunlight) strong enough to cause sunburn after eating, which can be fatal in the worst cases (buckwheat disease). The fruit contains almost no phagopyrin, so it is safe for humans.

But why does it contain such a special substance?

One theory suggests that these organisms developed this substance to eliminate moth larvae (Inoue, 2019).

Buckwheat pests, such as the larvae of the cutworm (Mamestra brassicae), feed on the leaves from the bottom up. During this process, they accumulate phagopyrin in their bodies. After this, the larvae move upwards to feed on the upper leaves, but at this point, they are exposed to sunlight, which causes oxidative damage and leads to death.

Armyworms occasionally cause massive outbreaks in buckwheat fields, but these outbreaks rarely continue into the following year. This is thought to be due to the effects of phagopyrin and the nuclear polyhedrosis virus.

What is the structure of a flower?

Buckwheat flowers bloom from August to October, producing short racemes at the tops of stems and branches, and are white or pale pink in color. They lack petals, and the calyx is deeply five-lobed, containing five stamens and three pistils, with eight yellow nectaries at their base (Cawoy et al., 2009). Nectar droplets accumulate in these nectaries. This suggests that nectar is a greater reward for insects than pollen. The fruit is an achene, triangular-pyramidal in shape.

Each flower typically blooms for only one day, and they open either from the bottom to the top of the raceme. The number of flowers per day reaches its peak approximately 2 to 3 weeks after the first bloom.

Buckwheat flowers possess a characteristic called "heterostyle." This means that the plant has two types of flowers: short-styled flowers (where the pistil is shorter than the stamens) and long-styled flowers (where the pistil is longer than the stamens). Pollination between flowers of the same type will not result in fertilization (self-incompatibility). This preserves genetic diversity and makes the plant more resilient to environmental changes.

In areas near its native habitat, hoverflies and bees visit the flowers, while in cultivated areas, honeybees do.

Buckwheat flowers are almost entirely pollinated by insects, with only 1% of pollination occurring by wind (Cawoy et al., 2009). A variety of insects visit the flowers, including flies, moths, bees, and lacewings.

However, perhaps due to the abundance of nectar, honeybees are the dominant species in buckwheat cultivation areas in many countries. It is likely that the European honeybee (Apis mellifera) is the most common. Therefore, beekeepers sometimes recommend introducing honeybee hives to increase buckwheat yields. Honey made from buckwheat nectar is popular in the Brittany region of France due to its soy sauce-like aroma and unique color, which comes from its high polyphenol content.

However, since it is originally from China, it is unlikely that insects like European honeybees are the primary pollinators.

A study in China found that while honeybees accounted for 35%, other bees (bumblebees, small bees, rhinoceros bees, and leafcutter bees) made up 25%, and syrphidae (shrews) accounted for 27%. Another study in Japan, although not in its native habitat, found the results to be even more pronounced, with honeybees making up only 2-5%.

These observations suggest that they originally relied on various bees and hoverflies for pollination. My theory is that in their native mountainous region, temperatures and atmospheric pressure are low, and small bees and hoverflies are relatively resistant to cold, which may explain this outcome.

Were wild insects essential for increasing buckwheat yields?

However, even if that is the case in its native habitat, cultivated areas like Japan may not feel the need for "wild insects" to that extent. As mentioned above, domesticated European honeybees, which are not originally found in Japan, perform pollination to a certain extent.

However, research by the Forestry and Forest Products Research Institute in Japan has revealed that this is not the case (Taki et al., 2010).

In Hitachiota City, Ibaraki Prefecture, a survey was conducted on the types and number of insects visiting flowers and the fruiting rate of buckwheat in various buckwheat fields with different surrounding environments. The results showed that buckwheat fields surrounded by rich biodiversity such as forests and grasslands had a higher number of "wild insects" that pollinate the flowers, resulting in a better fruiting rate.

Insects other than honeybees do not have very wide foraging ranges. They move within a range of several hundred meters from forests and grasslands. In other words, to increase yields, forests and grasslands are necessary within several hundred meters of buckwheat fields.

To put it more simply, in order to eat plenty of buckwheat, we need to conserve nature . These invisible benefits we receive from nature are called "ecosystem services." If you enjoy eating buckwheat, it seems you should be more mindful of these things, rather than just slurping your noodles without thinking!

Were there other hidden visitors to the flowers?

While the insects mentioned above are the main species that visit the area, some have also pointed out the importance of other insects.

The common skipper butterfly, Parnara guttata, is also known as the "buckwheat butterfly" in Shinshu. While its larvae are pests of rice, farmers believe that the adults play a vital role in buckwheat pollination (Inoue, 2019). For farmers, it may be a troublesome insect with both advantages and disadvantages. However, since butterflies often steal nectar, it's unclear how much they actually contribute to pollination, but if they do, it would be an interesting phenomenon.

Furthermore, it has been found that a considerable number of "parasitic wasps," a group of wasps that parasitize other insects, also come to buckwheat in search of nectar and pollen (Inagaki et al., 2013). Since much of the research on pollination ecology focuses on honeybees, it is possible that parasitic wasps play an even more important role in adulthood, not just in buckwheat.

Why does buckwheat self-pollinate?

While cross-pollination is essential for buckwheat, Tartary buckwheat (French buckwheat) self-pollinates, producing only a small number of flowers in the leaf axils. In other words, unlike buckwheat, it does not require insects for pollination.

Why does buckwheat self-pollinate?

It is thought that this is because they evolved as pioneer plants that were among the first to invade areas with less competition from other plants (Inoue, 2019).

Pioneer plants can quickly invade and reproduce in bare ground, and in the short term, they are extremely prolific. In this respect, they have an advantage over buckwheat.

Furthermore, because they inhabit areas at even higher altitudes than buckwheat, they are exposed to strong ultraviolet radiation and low temperatures, resulting in fewer pathogens and pests, and thus allowing for less genetic diversity.

Conversely, buckwheat can grow in areas with high humidity and bad weather, so it is thought that it needs to maintain genetic diversity to resist pathogens and pests.

Are the fruits achenes and the seeds dispersed by wind and animal feeding?

The fruit is an achene, common to all species in the genus Buckwheat (Wu et al., 2003). The achene has a hard, membranous pericarp, which is the so-called "buckwheat hull," and when ripe it dries out, containing one seed in each chamber. The seed coat is called the "cocolate," and the delicious part containing starch is the "endosperm," which is the seed's primary source of nutrition.

Buckwheat achenes protrude from the persistent perianth, are dark brown, dull, ovate, sharply triangular, 5-6 mm long, and flat-surfaced. They mature in 3 months. This is what is called "unhulled buckwheat."

The achenes of buckwheat protrude from the persistent perianth, are dark brown, oblong-ovate, 5-6 mm long, with three ridges, grooves on the surface, rounded corners below the middle, sharp corners at the top, and curved teeth at the corners.

The achenes of *Polygonum cuspidatum* are dark brown, blunt, broadly ovate, 6-8 mm long, triangular, sometimes with narrow wings, with smooth to wavy corners and an acute apex.

Seeds are a very important part of a plant because they are edible, but how do they disperse in nature?

First, it's safe to assume that the three ridges or wings on buckwheat achenes are clearly developed to catch the wind. If buckwheat achenes are harvested late, they are destroyed by the wind, scattering the seeds (Campbell, 1997).

Furthermore, it has been pointed out that the hard pericarp (buckwheat hull) also plays a role in being eaten by ruminants and passing through their gastrointestinal tract undigested. In other words, it is a form of dispersal by animal aquaculture (Spengler, 2020).

What are the differences, roles, functions, and ways to remember the stomachs of ruminants (tripe, honeycomb tripe, omasum, and abomasum)? Why did rumination evolve?

When you go to a yakiniku (Japanese barbecue) restaurant, you might see four parts of the cow's stomach (fore-stomach) listed as offal: mino, hachinosu, senmai, and giara. Because they have a distinctive taste and are internal organs, people either love them or hate them, but their chewy texture and compatibility with alcohol make them a popular choice...

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However, if they truly evolved to be dispersed only by wind or animal feeding, it would be difficult to explain why their seeds are so large and contain a significant amount of starch.

While a large endosperm containing starch might seem to have only advantages, it makes the seeds heavier for wind dispersal and increases the risk of them being destroyed and digested by animals if they are dispersed by aquaculture.

For these reasons, it is believed that when plants were domesticated by humans, that is, when selective breeding was carried out to a level where evolution occurred, the seeds became larger, lost dormancy, and the seed coat thinned to suit human needs.

References

Campbell, CG 1997. Buckwheat: Fagopyrum esculentum Moench (Vol. 19). International Plant Genetics Research Institute, 93pp. ISBN: 9789290433453

Cawoy, V., Ledent, JF, Kinet, JM, & Jacquemart, AL 2009. Floral biology of common buckwheat (Fagopyrum esculentum Moench). The European Journal of Plant Science and Biotechnology 3(1): 1-9. ISSN: 1752-3842, http://www.globalsciencebooks.info/Online/GSBOnline/images/0906/EJPSB_3(SI1)/EJPSB_3(SI1)1-9o.pdf

Gondola, I., & Papp, PP 2010. Origin, geographical distribution and phylogenic relationships of common buckwheat (Fagopyrum esculentum Moench.). The European Journal of Plant Science and Biotechnology 4(1): 17-32. ISSN: 1752-3842, http://globalsciencebooks.info/Online/GSBOnline/images/2010/EJPSB_4(SI1)/EJPSB_4(SI1)17-32o.pdf

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

Inagaki, E., Saiki, C., Matsuno, K., & Ichihara, M. 2013. Pollinating Hymenoptera observed on buckwheat flowers in Shizuoka Prefecture. Research Report of Shizuoka Prefectural Agricultural and Forestry Research Institute 6: 65-69. https://agriknowledge.affrc.go.jp/RN/2010851714

Inoue, Naoto. 2014. The Science of Delicious Grains: From Rice, Wheat, and Corn to Buckwheat and Other Grains. Kodansha, Tokyo. 222pp. ISBN: 9784062578691

Inoue, Naoto. 2019. Sobalogy: From Food Science to Folklore. Shibata Shoten, Tokyo. 287pp. ISBN: 9784388353552

Spengler, RN 2020. Anthropogenic seed dispersal: rethinking the origins of plant domestication. Trends in Plant Science 25(4): 340-348. https://doi.org/10.1016/j.tplants.2020.01.005

Taki, H., Okabe, K., Yamaura, Y., Matsuura, T., Sueyoshi, M., Makino, SI, & Maeto, K. 2010. Effects of landscape metrics on Apis and non-Apis pollinators and seed set in common buckwheat. Basic and Applied Ecology 11(7): 594-602. ISSN: 1439-1791, https://doi.org/10.1016/j.baae.2010.08.004

Yamato, Shohei. 2014. Interaction between Christianity and Buddhism in the earliest period of the Christian era. Christ and the World: Bulletin of Tokyo Christian University 24: 109-139. ISSN: 0916-9881, http://id.nii.ac.jp/1131/00000022/

Wu, ZY, Raven, PH & Hong, DY (Eds.). 2003. Flora of China (Vol. 5 Ulmaceae through Basellaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis. ISBN: 9781935641056