Someiyoshino (ソメイヨシノ)

Someiyoshino (scientific name: Prunus x yedoensis) is a type of cherry tree as a garden plant, having been produced by crossbreeding Cerasus spachiana 'Komatsuotome' in the line of Edohigan (P. pendula Maxim. f. ascendens (Makino) Ohwi) and the Oshima cherry (P. lannesiana var. speciosa). Today it's a representative type of ornamental cherry tree, and occasionally it's written as 'Yoshinozakura' (Yoshino cherry).
Additionally, sometimes all the plants that were born by crossbreeding Edohigan and Oshima cherries are called 'Someiyoshino,' and Someiyoshino in a narrow sense is sometimes written as the binominal 'Someiyoshino 'Someiyoshino.'
In this section, Someiyoshino is described in the narrow sense.

Origin of the name

In the time from the end of the Edo period to the beginning of the Meiji period, it was raised by gardeners and artisans of garden trees who had established a colony in Somei Village, in Edo (the present-day Komagome, Toshima Ward, Tokyo Prefecture), and was sold as 'Yoshinozakura' (meaning Yamazakura, or Prunus jamasakura).
Through research conducted by Yorinaga FUJINO, it was discovered that it was distinct from Yamazakura, and in 1900 it was referred to as 'Someiyoshino' in 'Japanese Gardening Magazine.'
It is said that it was initially called 'Yoshino' after Mt. Yoshino-yama in Yamato Province (a mountainous district in Nara Prefecture), which is a place noted for its cherry blossoms; however, since there was concern that the name 'Yoshino (Yoshinozakura)' would be confused with Yamazakura, which grows a lot in Mt. Yoshino-yama, Dr. Yorinaga FUJINO, who had conducted research on the cherry trees of Ueno Park, called it 'Someiyoshino' in 'Japanese Gardening Magazine.'

Characteristics

Someiyoshino, Prunus x yedoensis, is likely to have as its origin the hybrid between Edohigan, P. pendula Maxim. f. ascendens (Makino) Ohw, and Oshima Cherry, P. lannesiana var. speciosa. Furthermore, the x in scientific names is a way to indicate a natural hybrid, and it's said that the sign isn't not used in regard to artificial hybrids. It isn't known whether Someiyoshino is a natural hybrid or an artificial hybrid, but some opinions have expressed doubt regarding the validity of this scientific name. One finding of research states that it's a hybrid of Komatsuotome instead of Edohigan; however, Komatsuotome is also a gardening type of Edohigan as well as being a clone.

Characteristics in appearance

There are five petals, and before the leaves grow out the flowers open and enter full bloom. The flowering period is around the end of March in the Kyushu region. The color of the flowers is pink when they start to open, but they whiten as they approach full bloom. Like Edohigan, one of its ancestors, only flowers crowd together and cover the entire canopy of the tree at full bloom, but the flowers are bigger and more showy than those of Edohigan. It's a type having the characteristics of Edohigan, in which the flowers open before the leaves grow, and the Oshima cherry, in which the flowers are large and well proportioned.

The color of the calyx tube is red, and it's shaped like a pot. The tree is approximately 10 to 15 meters in height. It is very commonly planted because it blooms with flowers even as a young tree.

It doesn't propagate naturally by seed.

Someiyoshino does not propagate by seed. All the trees in many places are bred by people's hands through means of grafting and other techniques.

There is also a theory that since it's a first filial hybrid, the fruition rate of self-pollination is extremely low. However, it's somewhat likely that, as a result of hybridization and crossbreeding, self-incompatibility (of the plant) has become very apparent in this type. Actually, under certain branch conditions a considerable rate of fruition can be seen in some cases. However, even in such a case the seeds that were born through self-pollination do not germinate. Consequently, a genuine descendent of Someiyoshino cannot exist.

However, it is possible to crossbreed with cherry trees other than Someiyoshino, and sometimes it makes fruition and the seeds germinate. However, in this case, even if it has strongly inherited the genetic characteristics of Someiyoshino, the genetic characteristics will change and it will become a type other than Someiyoshino. Because of this, a cherry tree that has been grown from the seed of Someiyoshino can't be called Someiyoshino.
There are seeds that can be taken from Someiyoshino, but currently there is no 'seed that will grow up to be Someiyoshino.'

Further, as seedling descendants between Someiyoshino and other brands of cherry trees, there are nearly a hundred kinds of subspecies confirmed, such as Mizutamazakura (Cerasus 'Manadzuru-littorea'), Usugeoshima (Cerasus x yedoensis 'Candida'), Showazakura (Cerasus x yedoensis 'Syouwa-zakura'), Someinioi (Cerasus x yedoensis 'Somei-nioi'), and Sotoorihime (Cerasus x yedoensis 'Sotorihime').
Additionally, there are types of cherry trees referred to as being of the 'Sakuraedohigan group.'
These types are said to be bred in America from the seedlings of Someiyoshino that were sent to America to represent the friendship between Japan and the U.S.A.

Breeding by the hands of people

The characteristic inability to make seeds means it can't be spread without human intervention. Generally, Someiyoshino is propagated by grafting onto other stock, planting cuttings and transplantation. Therefore, it's inseparably related to human beings, and it has been distributed as a human activity.

Looking back at the time, all Someiyoshino trees are linked to a single tree, and all Someiyoshino can be called clones of that Someiyoshino. This is the reason that all Someiyoshino trees bloom and drop their flowers at the same time, but it's also the reason for weakness against environmental changes and certain diseases.

Popularity and topicality

Because Someiyoshino is much more likely to be seen along the streets than other types, disputes between enthusiasts have occurred continuously from the past in regard to its origin as to whether it's right or wrong, as well as in regard to people's likes and dislikes. Historically, it's assumed to have been born in the middle through late Edo period as a type of garden plant. Given the characteristics in which its flowers bloom before the leaves mature and the blooms are showy and therefore loved by people, it spread gradually from the Meiji period on, and after further being planted at a terrific pace on the devastated lands of the country after World War II, it came to be the most popular cherry tree in Japan. It's still the most popular cherry tree in Japan, being planted in nearly every area of the country, and the 'bloom forecast' (cherry blossom front) which is announced in March of every year by the Japan Meteorological Agency is based on the bloom condition of this type.

Various theories about the origin

Someiyoshino was established as a type of garden plant in the middle though late Edo period. There are theories that it was selected and bred artificially by gardeners, or that the natural hybrid tree was propagated by gardeners who planted cuttings. Also, among American botanists there are some who advocate the theory that Someiyoshino is an independent type instead of a hybrid between the Oshima cherry and Edohigan.

The Izu Peninsula theory

In 1916, Ernest Henry Wilson, an American whose name is commemorated at the Wilson stump in Yaku-shima Island, advocated the theory that it's a hybrid between the Oshima cherry and Edohigan; moreover, through the crossbreeding experiment by Kaname TAKENAKA of National Institute of Genetics (published in 1965) it was discovered that Someiyoshino and its subspecies could be seen among the hybrids between the Oshima cherry and Edohigan. Accordingly, in the case where the spontaneous theory was adopted, from the distribution conditions of the Oshima cherry and Edohigan, the Izu Peninsula theory was advocated, stating that it had sprung up in the area around the peninsula. However, based on local investigation there is less possibility of its being a natural hybrid.

The Korean origination theory

There was a theory regarding the Osakura (王桜), of Korea, as the origin of Someiyoshino, but in 2007 it was confirmed through genetic research by the U.S. Department of Agriculture that the Osakura of Korea is peculiar to Korea and is a different species from the Someiyoshino of Japan, and consequently this theory has been thoroughly refuted. However, in the Republic of Korea there are still activities that advocate the theory that 'Osakura equals Someiyoshino' and therefore plant Someiyoshino in places where Osakura naturally grow, and in fact the extinction of Osakura--a species native to Korea--is feared.

In 1939, Genichi KOIZUMI pointed out the similarity with Osakura in Jeju, of the Republic of Korea, and advocated a theory that regarded Jeju as the place of spontaneous growth and origin, but since there is no extant pressed flower specimen, which is said to have been used by Koizumi to compare Someiyoshino and Osakura, this theory has been doubted since the beginning. Additionally, Someiyoshino has the form of crossbreeding of the Oshima cherry and Edohigan as well as certain genetic similarities to the Oshima cherry and Edohigan, and since the Oshima cherry is an island form of Kasumizakura (Prunus Leveilleana Koene) that evolved in the Izu Island chain and doesn't exist in the Korean Peninsula, the theory was disadvantageous from this perspective too. The 'Christianity Daily' states, 'We wish readers to visit sites that have worldwide influence and amend an error about Korea, and place a way to rewrite enCherry blossom.

However on April 10, 2009, the Joong Ang Daily, one of three great newspapers in Korea, regarded the origin of Someiyoshino as that country's Yoi Island. Further, many Korean scholars insist that the cherry tree originated in Korea instead of Japan.

The artificial breeding theory

Against this theory, given a record stating that Someiyoshino, reaching the age of 100, had been planted in Koishikawa Botanical Gardens, and the record of a gardener in Somei Village (the present-day Komagome, Toshima Ward, Tokyo Prefecture) stating that Someiyoshino was bred, Fumio IWASAKI and others advocate the theory that regards Somei Village as the place of origin. Based on the gardener's record, there is an assumption that sometime in the period from 1720 from 1735, ITO Ihei Masatake, who had lived in Komagome and whose tomb is at Saifuku-ji Temple, artificially bred and grew Someiyoshino. This gives credibility to the assertion that Somei Village is the place of origin.

In March 2007, a group comprised of researchers from Chiba University, Shizuoka University and elsewhere announced that, based on the results of genetic analysis, Someiyoshino was likely to have been born by crossbreeding the Oshima cherry and Komatsuotome, which is a gardening type of Edohigan.
111th Lecture
4/5 page (site of Nakanishi Printing Company) PDF files.

Masayuki HASHIMOTO, a lecturer at Iwate Univesity (who died on November 25, 2003, at the age of 75), followed the theory by Kaname TAKENAKA but couldn't breed a cherry tree similar to Someiyoshino; however, based on advice by Hashimoto, Ikuo NAKAMURA and others, from the DNA analysis, he crossbred the Oshima cherry and Komatsuotome of Ueno Onshi Koen park and planted five trees in pots at Chiba University's Faculty of Horticulture, expecting them to be reappear four or five years later (2012 or 2013) as Someiyoshino.

Use

It is broadly planted in streets, flood plains and parks. It's popular as the tree most commonly used to encourage blossom viewing.

Diseases, etc.

As is a common fault of cherry trees, it's pointed out that Someiyoshino too has low resistance to air pollution such as exhaust gas, and that it's easily damaged by disease and insects. Because all the individuals are clones, it has low ability to acquire greater tolerance.

Witch's broom disease

It's more easily infected by witch's broom disease than other cherry trees are. Witch's broom disease will strike when the cherry tree is infected by Taphrina wiesneri, an ascomycete with a form of saccharomycete, and at the top part of the tree twigs gather up and make what is called a 'nest of tengu' (nest of long-nosed goblin, or a witch's broom). Further, because small leaves begin to grow as the flowers reach full bloom, they become an eyesore and subject the tree to damage because the infected area will die within a period of several years. The infected branches must be cut off and burned.

Damage due to mushrooms

Increasingly, there are cases in which white-rot fungus (such as bracket fungus) propagates and the infected trees must be cut down; particularly, the trees planted in parks and streets are in serious condition. This kind of symptom can't be recognized from outside, so a special device must be used for diagnosis.

Damage by America Shirohitori (Hyphantria cunea)

Damage is done to the leaves when America Shirohitori consumes them, and sometimes the vitality of the tree is reduced, particularly in the case of an old tree. Because America Shirohitori grow as a group in the nest net, which is on the back of the leaves, until they reach their final form as worms, they are removed directly by cutting off the affected branches and leaves before they grow up to be imagoes, or are exterminated by spraying an appropriate amount of insecticide such as fenitrothion or emulsion of acephate.

Reduction of tree vitality due to the environment
Not only are air pollution by exhaust gas but global warming and the heat-island phenomenon are also indirect causes of illness among Someiyoshino trees, since they can't keep up with the rapid pace of environmental change. The pavement of ground around the roots also reduces the vitality of the tree.

Additionally, being the most popular tree for flower viewing can be called an indirect cause of disease. The excessive compacting of the soil around the roots due to foot traffic can't be good for the tree, either. Furthermore, bad manners influence the trees. The use of fire beneath the tree, such as in grilling meat and barbecuing, has a negative influence and should therefore be avoided. On top of that, people who view the flowers should absolutely be prohibited from breaking and cutting the branches of the trees. It can be said in general for cherry trees, but since it tends to rot at the site of a broken branch, people untrained in tree care should refrain from breaking and cutting the branches. It is important that the areas where branches have been broken and cut are protected from the propagation of miscellaneous germs, so that rot can be prevented.

Life span

Someiyoshino has a major fault. Compared with Yamazakura and Edohigan, which can live for several hundred years, there are fewer old trees.
There is even a popular belief called the 'sixty-year lifespan theory.'
Although the lifespan isn't known because there are no statistics, the tree that reaches a large diameter is theoretically believed to have an unlimited lifespan.

The reason for having fewer old trees is not clear, but there is a theory that 'Someiyoshino ages quickly because it grows rapidly'; it has been pointed out that the damage by exhaust gas and other factors occurring in the streets, or the fact that the trees are likely to be planted in places where they're easily trashed, such as parks, seem to have become the factors that reduce the Someiyoshino's lifespan. Because Someiyoshino is propagated by grafting, it is theorized that since Yamazakura--the stock for grafting--rots, the center of the tree also rots and thereby shortens the lifespan. It has also been pointed out that because all Someiyoshino have same characteristics, all Someiyoshino have poor resistance to disease and environmental changes, and consequently they wither at the same time.

Contrary to that assertion, there are indeed old Someiyoshino trees to be found. A Someiyoshino in Tokyo Prefecture's Kinuta Park was planted in 1935, so more than 70 years have already passed. Additionally, in Hirosaki City, Aomori Prefecture, due to the use of apple-tree pruning techniques on Someiyoshino as a means to recover their vitality, many Someiyoshino have returned to health. However, attention must be paid to management, such as by pruning immediately after the leaves change color and fall in order to change the C/N (carbon/nitrogen) ratio, and by promoting the growth of narrow roots by digging around them and modifying the soil. In Hirosaki Park (at the ruins of Hirosaki Castle), there is a Someiyoshino more than a century old, and this is said to be the oldest tree existing among this species. Further, this Someiyoshino was planted in 1882 by Tatee KIKUCHI, who is said to be the 'founder of Aomori apples'; he was also a great-grandfather of the physicist Makoto KIKUCHI (Osaka University), who is known for his criticism against pseudoscience.

Propagation by human hands extends the life of the Someiyoshino, and thus it's also able to blossom through the work of human hands.