Bonsai (盆栽, lit. plantings in tray, from bon, a tray or low-sided pot and sai, a planting or plantings, pronunciation (help·info)) is a Japanese art form using miniature trees grown in containers. Similar practices exist in other cultures, including the Chinese tradition of penjing from which the art originated, and the miniature living landscapes of Vietnamese hòn non bộ. The Japanese tradition dates back over a thousand years, and has its own aesthetics and terminology.
"Bonsai" is a Japanese pronunciation of the earlier Chinese term penzai. A "bon" is a tray-like pot typically used in bonsai culture. The word bonsai is often used in English as an umbrella term for all miniature trees in containers or pots. This article focuses on bonsai as defined in the Japanese tradition.
The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower). By contrast with other plant cultivation practices, bonsai is not intended for production of food, for medicine, or for creating yard-size or park-size gardens or landscapes. Instead, bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container.
A bonsai is created beginning with a specimen of source material. This may be a cutting, seedling, or small tree of a species suitable for bonsai development. Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species that produces true branches and can be cultivated to remain small through pot confinement with crown and root pruning. Some species are popular as bonsai material because they have characteristics, such as small leaves or needles, that make them appropriate for the compact visual scope of bonsai.
The source specimen is shaped to be relatively small and to meet the aesthetic standards of bonsai. When the candidate bonsai nears its planned final size it is planted in a display pot, usually one designed for bonsai display in one of a few accepted shapes and proportions. From that point forward, its growth is restricted by the pot environment. Throughout the year, the bonsai is shaped to limit growth, redistribute foliar vigor to areas requiring further development, and meet the artist's detailed design.
The practice of bonsai is sometimes confused with dwarfing, but dwarfing generally refers to research, discovery, or creation of plant cultivars that are permanent, genetic miniatures of existing species. Bonsai does not require genetically dwarfed trees, but rather depends on growing small trees from regular stock and seeds. Bonsai uses cultivation techniques like pruning, root reduction, potting, defoliation, and grafting to produce small trees that mimic the shape and style of mature, full-size trees.
Early versions 
The lineage of bonsai derives from the Chinese penjing. Imperial embassy personnel and Buddhist students from Japan had been returning from mainland China with many souvenirs, including occasional container planting, since the 6th century. At least 17 diplomatic missions were specifically sent from Japan to the Tang court between the years 603 and 839.
Japan's historical Shōsōin, which houses 7th, 8th, and 9th-century artifacts including material from Japan's Tempyō period, contains an elaborate miniature tree display dating from this time. This artifact is composed of a wooden tray serving as a base, carved wooden mountain models, and sand portraying a riverine sandbar. Small tree sculptures in silver metal are meant to be placed in the sand, to produce a table-top depiction of a treed landscape. While this display is closer to the Japanese bonkei display than to a living bonsai, it does reflect the period's interest in miniature landscapes.
From about the year 970 comes the first lengthy work of fiction in Japanese, Utsubo Monogatari (The Tale of the Hollow Tree), which includes this passage: "A tree that is left growing in its natural state is a crude thing. It is only when it is kept close to human beings who fashion it with loving care that its shape and style acquire the ability to move one." The idea, therefore, was already established by this time that natural beauty becomes true beauty only when modified in accordance with a human ideal.
In the medieval period, recognizable bonsai began to appear in handscroll paintings like the Ippen shonin eden (1299). Saigyo Monogatari Emaki was the earliest known scroll to depict dwarfed potted trees in Japan. It dates from the year 1195, in the Kamakura period. Wooden tray and dish-like pots with dwarf landscapes on modern-looking wooden shelf/benches are shown in the 1309 Kasuga-gongen-genki scroll. These novelties show off the owner's wealth and were probably exotics imported from China.
Chinese Chan Buddhist monks also came over to teach at Japan's monasteries, and one of the monks' activities was to introduce political leaders of the day to the various arts of miniature landscapes as ideal accomplishments for men of taste and learning.
The c.1300 rhymed prose essay, Bonseki no Fu (Tribute to Bonseki) written by celebrated priest and master of Chinese poetry, Kokan Shiren (1278–1346), outlined the aesthetic principles for what would be termed bonsai, bonseki and garden architecture itself. At first, the Japanese used miniaturized trees grown in containers to decorate their homes and gardens.
Criticism of the interest in curiously twisted specimens of potted plants shows up in one chapter of the 243-chapter compilation Tsurezuregusa (c.1331). This work would become a sacred teaching handed down from master to student, through a limited chain of poets (some famous), until it was at last widely published in the early 17th century. Before then, the criticism had only a modest influence on dwarf potted tree culture.
In 1351, dwarf trees were displayed on short poles as portrayed in the Boki Ekotoba scroll. Several other scrolls and paintings also included depictions of these kinds of trees. Potted landscape arrangements made during the next hundred years or so included figurines after the Chinese fashion in order to add scale and theme. These miniatures would eventually be considered garnishes[disambiguation needed] decidedly to be excluded by Japanese artists who were simplifying their creations in the spirit of Zen Buddhism.
Around the 14th century, the term for dwarf potted trees was "the bowl's tree" (鉢の木, hachi-no-ki). This denoted the use of a fairly deep pot, as opposed to the shallow pot denoted by the term bonsai.
Hachi-No-Ki (The Potted Trees) is also the title of a Noh play by Zeami Motokiyo (1363–1444), based on a story from c. 1383. It tells of an impoverished samurai who sacrifices his three last dwarf potted trees as firewood to provide warmth for a traveling monk on a winter night. The monk is an official in disguise who later rewards the samurai by giving him three lands whose names include the names of the three types of trees the samurai burnt: ume (plum), matsu (pine), and sakura (cherry). In later centuries, woodblock prints by several artists would depict this popular drama. There was even a fabric design of the same name.
Stories referring to bonsai began to appear more frequently by the 17th century. Shogun Tokugawa Iemitsu (r. 1623-1651) was a hachi-no-ki enthusiast. A story tells of Okubo Hikozemon (1560–1639), councilor to the shogun, who threw one of Iemitsu's favorite trees away in the garden—in sight of the shogun—in order to dissuade him from spending so much time and attention on these trees. In spite of the servant's efforts, Iemitsu never gave up his beloved art form. Another story from this time tells of a samurai's gardener who killed himself when his master insulted a hachi-no-ki of which the artisan was especially proud.
Bonsai dating to the 17th century have survived to the present. One of the oldest-known living bonsai trees, considered one of the National Treasures of Japan, is in the Tokyo Imperial Palace collection. A five-needle pine (Pinus pentaphylla var. negishi) known as Sandai-Shogun-No Matsu is documented as having been cared for by Tokugawa Iemitsu. The tree is thought to be at least 500 years old and was first trained as a bonsai by, at latest, the year 1610. The earliest known report by a Westerner of a Japanese dwarf potted tree was made in 1692 by George Meister.
Chinese bonsai containers exported to Japan during the 17th and 18th centuries would become referred to as Kowatari ("old crossing"). These were made between 1465 and about 1800. Many came from Yixing in Jiangsu province—unglazed and usually purplish-brown—and some others from around Canton, in particular, during the Ming dynasty. Miniature potted trees were called hachi-ue in a 1681 horticulture book. This book also stated that everyone at the time grew azaleas, even if the poorest people had to use an abalone shell as a container. Torii Kiyoharu's use of woodblock printing in Japan depicted the dwarf potted trees from horticultural expert Itō Ihei's nursery.
By the end of the 18th century, bonsai cultivation was quite widespread and had begun to interest the public. In the Tenmei era (1781–88), an exhibit of traditional dwarf potted pines began to be held every year in Kyoto. Connoisseurs from five provinces and neighboring areas would bring one or two plants each to the show in order to submit them to visitors for ranking.
Classical period 
In Itami, Hyogo (near Osaka), a group of scholars of Chinese arts gathered in the early 19th century to discuss recent styles in the art of miniature trees. Their version of these, which had been previously called "Bunjin Ueki," "Bunjin Hachiue," or other terms, were renamed "bonsai" (the Japanese pronunciation of the Chinese term penzai). This term had the connotation of a shallower container in which the Japanese could now more successfully style small trees. The term "bonsai," however, would not become regularly used in describing their dwarf potted trees for nearly a century. Many others terms and compositions adopted by this group were derived from Kai-shi-en Gaden, the Japanese version of Jieziyuan Huazhuan (Manual of the Mustard Seed Garden).
In 1829, a significant book that first established classical bonsai art, Somoku Kinyo Shu (A Colorful Collection of Trees and Plants/Collection of tree leaves), was published. It includes the basic criteria for the ideal form of the classical pine bonsai, in detail and with illustrations. That same year, small tako-tsuki (octopus-styled) trees with long, wavy-branches began to be offered by a grower in Asakusa Park, a north-eastern Edo suburb. Within 20 years that neighborhood became crowded with nurseries selling bonsai. The three-volume Kinsei-Jufu, possibly the first book of bonsai, tools, and pots, dates from 1833.
Numerous artists of the 19th century depicted dwarf potted trees in woodblock prints, including Yoshishige (who pictured each of the fifty-three classic stations of the Tokaido (road) as miniature landscape) and Kunisada (who included mostly hachi-no-ki in some four dozen prints). The earliest known photograph from Japan depicting a dwarf potted tree dates from c. 1861 by Pierre Rossier.
On October 13, 1868, the Meiji Emperor moved to his new capital in Tokyo. Bonsai were displayed both inside and outside Meiji Palace, where they have since remained important in affairs of the Palace. Bonsai placed in the grand setting of the Imperial Palace had to be "Giant Bonsai," large enough to fill the grand space. The Meiji Emperor encouraged interest in bonsai. Government officials who did not appreciate bonsai fell out of favor. Soon all members of the ministry had bonsai whether they liked the tradition or not. Prince Itoh was an exception: Any bonsai that the emperor gave him were then passed to Kijoji Itoh. Kijoji Itoh was a statesman of great influence behind the scenes, and a noted bonsai collector who conducted research and experiments on these bonsai.
Bonsai shaping aesthetics and techniques were becoming more sophisticated. By the late 1860s, thick combed and wetted hemp fibers were used to roughly shape the trunk and branches of miniature trees by pulling and tying them. The process was tedious and bothersome, and the final product was unsightly. Tips of branches would only be opened flat. Long, wavy-branched tako (octopus)-style trees were mass-produced and designed in the [renamed capital] Tokyo for the increasing foreign trade, while the more subtle and delicate bunjin-style trees designed in Kyoto and Osaka were for use in Japan. Tokyo preferred big trunks out of proportion and did not approve of Kyoto's finely designed slender trunks. (This cultural rivalry would continue for a century.)
Pots exported from China between 1816 and 1911 (especially the late 19th century) were called Nakawatari (middle-crossing) or Chuwatari, shallow rectangular or oval stoneware with carved feet and drainage holes. Unglazed pots of this type were used at ancestral shrines and treasured by the Chinese. After the mid-century, certain Japanese antiquities dealers imported them and instant popular approval for this type of container for bonsai created a huge demand. As a consequence, orders came from Japan to Yixing pottery centers specifically to make bonsai pots.
Through the later 19th century, Japanese participation in various international exhibitions introduced many in the U.S. and Europe to dwarf potted trees. Specimens from the displays went into Western hands following the closing of the fairs. Japanese immigrants to the U.S. West Coast and Hawaii Territory brought plants and cultivation experience with them. Export nurseries, the most notable one being the Yokohama Gardeners Association, provided increasingly good quality dwarf potted trees for Americans and Europeans—even if the buyers did not have enough information or experience to actually keep the trees alive long-term.
An Artistic Bonsai Concours was held in Tokyo in 1892 followed by the publication of a three-volume commemorative picture book. This demonstrated a new tendency to see bonsai as an independent art form. In 1903, the Tokyo association Jurakukai held showings of bonsai and ikebana at two Japanese-style restaurants. Three years later, Bonsai Gaho (1906 to c.1913), became the first monthly magazine on the subject. It was followed by Toyo Engei and Hana in 1907, and Bonsai in 1921.
By 1907, "on the outskirts of Tokio [dwarf] tree artists have formed a little colony of from twenty to thirty houses, and from this centre their work finds its way to all parts of the world." "Its secrets are handed down from father to son in a few families, and are guarded with scrupulous care."
In 1910, shaping with wire was described in the Sanyu-en Bonsai-Dan (History of Bonsai in the Sanyu nursery). Zinc-galvanized steel wire was initially used. Expensive copper wire was only used for trees that had real potential. Between 1911 and about 1940, mass-produced containers were exported from Yixing, China, and made to the specifications of Japanese dealers. These were called Shinto (new crossing or arrival) or Shin-watare. These were made for increasing numbers of enthusiasts. Some containers, including primitive style ones, were also being made in Formosa.
By 1914, "at the N.E. corner of Shiba Park is a permanent bazaar (the first of its kind established in Tokyo) where hosts of native-made gimcracks can be bought at fixed prices. The exhibits of potted plants and dwarf trees held here from time to time attract lovers of such things." Also this year, the first national annual bonsai show was held (through 1933) in Tokyo's Hibiya Park. During this period, the tokonoma in formal rooms and tea rooms became the main place for bonsai display. The shaped trees now shared space with other items such as scrolls, incense burners, Buddhist statues and tea ceremony implements.
The first issue of Bonsai magazine was published in 1921 by Norio Kobayashi (1889–1972). This influential periodical would run for 518 consecutive issues. Copper wire was being extensively used by this time. Major changes to a tree's shape could now be accomplished with wiring. Trees could be precisely and aesthetically wired, and then sold immediately. A greater number of both collected and nursery trees could now be trained for bonsai. The number of hobbyists increased due to the increased ability to style with wire, but there was also an increase in damaged or scarred trees.
The 1923 Great Kanto Earthquake and resulting fire devastated Tokyo, and gutted the downtown area where many bonsai were grown. And so, two years later, a group of thirty families of downtown Tokyo professional growers established the Ōmiya Bonsai Village, northeast of the capital. The first great annual public exhibition of trees was held at the Asahi Newspaper Hall in Tokyo in 1927. The first of the very prestigious Kokufu-ten exhibitions were held in Tokyo's Ueno Park, beginning in 1934. By the following year, tokonoma display principles allowed for bonsai to be shown for the tree's individual beauty, not just for its spiritual or symbolic significance.
By 1940, there were about 300 bonsai dealers in Tokyo, some 150 species of trees were being cultivated, and thousands of specimens annually were shipped to Europe and America. The first major book on the subject in English was published in the Japanese capital: Dwarf Trees (Bonsai) by Shinobu Nozaki (1895–1968). The first bonsai nurseries and clubs in the Americas were started by first and second-generation Japanese immigrants.
Caretaker of the Imperial bonsai collection, Kyuzo Murata (1902–1991), was one of very few persons allowed to take care of bonsai during the Pacific War. He gathered together and preserved many trees from the other Omiya growers and would water them under the protection of night. Throughout 1945, many old trees were the smallest casualties of the spring and summer napalm bombing of Tokyo (esp. March 9/10) and sixty-six other cities. Gardeners protected the Imperial collection trees from fire by pouring water over them after the Palace caught fire when neighboring areas were bombed on May 25/26. Following the surrender of Japan, there began the post-war re-evaluation and reviving of damaged collections of trees—including the Imperial—which would continue for over a decade as Japan was rebuilt. Many of the Omiya growers did not continue their vocation.
During the Allied Occupation of Japan (through 1952) U.S. officers and their wives could take courses in bonsai, bonkei, ikebana, and other traditional arts and crafts as arranged by General MacArthur's headquarters. Many of the older and limited varieties of trees were no longer available, and the bonsai considered in fashion changed partly because of this shortage. Copper wire now largely replaced ordinary iron wire for shaping the better trees, but the latter still would be used for mass-produced commercial bonsai.
Modern bonsai 
Following World War II, a number of trends made the Japanese tradition of bonsai more and more accessible to Western and world audiences. One key trend was the increase in the number, scope, and prominence of bonsai exhibitions. For example, the Kokufu-ten bonsai displays reappeared in 1947 after a four-year cancellation and became annual affairs. The displays continue to this day, and are by invitation only for eight days in February. In October 1964, a great exhibition was held in Hibya Park by the private Kokufu Bonsai Association, reorganized into the Nippon Bonsai Association, to mark the Tokyo Olympics. A commemorative album titled Gems of Bonsai and Suiseki was published in Japanese and English. Other countries began presenting bonsai exhibitions as well, with recurring events now taking place in Taiwan and a number of other Asian countries, Australia, the United States, several European countries, and others. Currently, Japan continues to host regular exhibitions with the world's largest numbers of bonsai specimens and the highest recognized specimen quality.
Another key trend was the increase in books on bonsai and related arts, now being published in English and other languages for audiences outside Japan. In 1952, Yuji Yoshimura, son of a leader in the Japanese bonsai community, collaborated with German diplomat and author Alfred Koehn to give demonstrations and the first formal bonsai courses opened to the public and outsiders in Tokyo. Koehn had been an enthusiast before the war, and his 1937 book Japanese Tray Landscapes had been published in English in Peking. Yoshimura's 1957 book The Art of Bonsai, written in English with his student Giovanna M. Halford, addressed both cultivation and aesthetic aspects of bonsai growing and went on to be called the “classic Japanese bonsai bible for westerners” with over thirty printings. The related art of saikei was presented to English-speaking audiences in 1963 in Kawamoto and Kurihara's Bonsai-Saikei. This book described tray landscapes made with younger material than was traditionally used in bonsai, providing an alternative to the use of large, older plants, few of which had escaped war damage.
Other works in Japanese and English had been published by this time, and afterward a tremendous number of books saw print. Translations and original volumes in over two dozen languages were published in the next few decades. The number of clubs outside of Asia increased once Japanese was no longer the sole language of bonsai, and interaction increased between members of all levels of experience.
A third trend was the increasing availability of expert bonsai training, at first only in Japan and then more widely. In 1967 the first group of Westerners studied at an Ōmiya nursery. Returning to the U.S., these people established the American Bonsai Society. Other groups and individuals from outside Asia then visited and studied at the various Japanese nurseries, occasionally even apprenticing under the masters. These visitors brought back to their local clubs the latest techniques and styles, which were then further disseminated. Japanese teachers also traveled widely, bringing hands-on bonsai expertise to all six continents.
By the beginning of the 1970s, these trends were beginning to merge. A large display of bonsai and suiseki was held as part of Expo '70, and formal discussion was made of an international association of enthusiasts. Three monthly magazines were started this year: Bonsai Sekai, Satsuki Kenkyu, and Shizen to Bonsai. In 1975, the first Gafu-ten (Elegant-Style Exhibit) of shohin bonsai (13-25 cm (9.84 in) (5–10 in) tall) was held. So was the first Sakufu-ten (Creative Bonsai Exhibit), the only event in which professional bonsai growers exhibit traditional trees under their own names rather than under the name of the owner. It was organized by Hideo Kato (1918–2001) at Daimaru Department Store in Tokyo.
The First World Bonsai Convention was held in Osaka during the World Bonsai and Suiseki Exhibition in 1980. Nine years later, the first World Bonsai Convention was held in Omiya and the World Bonsai Friendship Federation (WBFF) was inaugurated. These conventions attracted several hundreds of participants from dozens of countries and have since been held every four years at different locations around the globe: 1993, Orlando, Florida; 1997, Seoul, Korea; 2001, Munich, Germany; 2005, Washington, D.C.; 2009, San Juan, Puerto Rico.
The final trend supporting world involvement in bonsai is the widening availability of specialized bonsai plant stock, soil components, tools, pots, and other accessory items. Bonsai nurseries in Japan advertise and ship specimen bonsai world-wide. Most countries have local nurseries providing plant stock as well, although finding specimen bonsai is more difficult outside Japan and bonsai enthusiasts will often start with local trees that have not been pre-shaped into candidate bonsai. Japanese bonsai soil components, such as Akadama clay, are available worldwide, and local suppliers also provide similar materials in many locations. Specialized bonsai tools are widely available from Japanese and Chinese sources. Potters around the globe provide material to hobbyists and specialists in many countries.
Bonsai has now definitively reached a world-wide audience. There are over twelve hundred books on bonsai and the related arts in at least twenty-six languages available in over ninety countries and territories. A few dozen magazines in over thirteen languages are in print. Several score of club newsletters are available on-line, and there are at least that many discussion forums and blogs. Educational videos and just the appearance of dwarf potted trees in films and on television reach a wide audience. There are at least a hundred thousand enthusiasts in some fifteen hundred clubs and associations worldwide, as well as over five million unassociated hobbyists. Plant material from every location is being trained into bonsai and displayed at local, regional, national, and international conventions and exhibitions for enthusiasts and the general public.
Cultivation and care 
Bonsai cultivation and care requires techniques and tools that are specialized to support the growth and long-term maintenance of trees in small containers.
Material sources 
All bonsai start with a specimen of source material, a plant that the grower wishes to train into bonsai form. Bonsai practice is an unusual form of plant cultivation in that growth from seeds is rarely used to obtain source material. To display the characteristic aged appearance of a bonsai within a reasonable time, the source plant is often mature or at least partially grown when the bonsai creator begins work. Sources of bonsai material include:
- Propagation from a source tree through cuttings or layering.
- Nursery stock directly from a nursery, or from a garden centre or similar resale establishment.
- Commercial bonsai growers, which, in general, sell mature specimens that display bonsai aesthetic qualities already.
- Collecting suitable bonsai material in its original wild situation, successfully moving it, and replanting it in a container for development as bonsai. These trees are called yamadori and are often the most expensive and prized of all Bonsai.
The practice of bonsai development incorporates a number of techniques either unique to bonsai or, if used in other forms of cultivation, applied in unusual ways that are particularly suitable to the bonsai domain. These techniques include:
- Leaf trimming, the selective removal of leaves (for most varieties of deciduous tree) or needles (for coniferous trees and some others) from a bonsai's trunk and branches.
- Pruning the trunk, branches, and roots of the candidate tree.
- Wiring branches and trunks allows the bonsai designer to create the desired general form and make detailed branch and leaf placements.
- Clamping using mechanical devices for shaping trunks and branches.
- Grafting new growing material (typically a bud, branch, or root) into a prepared area on the trunk or under the bark of the tree.
- Defoliation, which can provide short-term dwarfing of foliage for certain deciduous species.
- Deadwood bonsai techniques called jin and shari simulate age and maturity in a bonsai.
Small trees grown in containers, like bonsai, require specialized care. Unlike houseplants and other subjects of container gardening, tree species in the wild, in general, grow roots up to several meters long and root structures encompassing several thousand liters of soil. In contrast, a typical bonsai container is under 25 centimeters in its largest dimension and 2 to 10 liters in volume. Branch and leaf (or needle) growth in trees is also large-scale in nature. Wild trees typically grow 5 meters or taller when mature, whereas the largest bonsai rarely exceed 1 meter and most specimens are significantly smaller. These size differences affect maturation, transpiration, nutrition, pest resistance, and many other aspects of tree biology. Maintaining the long-term health of a tree in a container requires some specialized care techniques:
- Watering must be regular and must relate to the bonsai species' requirement for dry, moist, or wet soil.
- Repotting must occur at intervals dictated by the vigour and age of each tree.
- Tools have been developed for the specialized requirements of maintaining bonsai.
- Soil composition and fertilization must be specialized to the needs of each bonsai tree, although bonsai soil is almost always a loose, fast-draining mix of components.
- Location and overwintering are also species-dependent, and it is important to note that few of the traditional bonsai species can survive inside a typical house.
Bonsai aesthetics are the aesthetic goals characterizing the Japanese tradition of growing an artistically shaped miniature tree in a container. Many Japanese cultural characteristics, in particular the influence of Zen Buddhism and the expression of Wabi-sabi, inform the bonsai tradition in Japan. Established art forms that share some aesthetic principles with bonsai include penjing and saikei. A number of other cultures around the globe have adopted the Japanese aesthetic approach to bonsai, and, while some variations have begun to appear, most hew closely to the rules and design philosophies of the Japanese tradition.
Over centuries of practice, the Japanese bonsai aesthetic has encoded some important techniques and design guidelines. Like the aesthetic rules that govern, for example, Western common practice period music, bonsai's guidelines help practitioners work within an established tradition with some assurance of success. Simply following the guidelines alone will not guarantee a successful result. Nevertheless, these design rules can rarely be broken without reducing the impact of the bonsai specimen. Some key principles in bonsai aesthetics include:
- Miniaturization: By definition, a bonsai is a tree kept small enough to be container-grown while otherwise fostered to have a mature appearance.
- Proportion among elements: The most prized proportions mimic those of a full-grown tree as closely as possible. Small trees with large leaves or needles are out of proportion and are avoided, as is a thin trunk with thick branches.
- Asymmetry: Bonsai aesthetics discourage strict radial or bilateral symmetry in branch and root placement.
- No trace of the artist: The designer's touch must not be apparent to the viewer. If a branch is removed in shaping the tree, the scar will be concealed. Likewise, wiring should be removed or at least concealed when the bonsai is shown, and must leave no permanent marks on the branch or bark.
- Poignancy: Many of the formal rules of bonsai help the grower create a tree that expresses Wabi-sabi, or portrays an aspect of mono no aware.
A bonsai display presents one or more bonsai specimens in a way that allows a viewer to see all the important features of the bonsai from the most advantageous position. That position emphasizes the bonsai's defined "front", which is designed into all bonsai. It places the bonsai at a height that allows the viewer to imagine the bonsai as a full-size tree seen from a distance, siting the bonsai neither so low that the viewer appears to be hovering in the sky above it nor so high that the viewer appears to be looking up at the tree from beneath the ground. Peter Adams recommends that bonsai be shown as if "in an art gallery: at the right height; in isolation; against a plain background, devoid of all redundancies such as labels and vulgar little accessories."
For outdoor displays, there are few aesthetic rules. Many outdoor displays are semi-permanent, with the bonsai trees in place for weeks or months at a time. To avoid damaging the trees, therefore, an outdoor display must not impede the amount of sunlight needed for the trees on display, must support watering, and may also have to block excessive wind or precipitation. As a result of these practical constraints, outdoor displays are often rustic in style, with simple wood or stone components. A common design is the bench, sometimes with sections at different heights to suit different sizes of bonsai, along which bonsai are placed in a line. Where space allows, outdoor bonsai specimens are spaced far enough apart that the viewer can concentrate on one at a time. When the trees are too close to each other, aesthetic discord between adjacent trees of different sizes or styles can confuse the viewer, a problem addressed by exhibition displays.
Exhibition displays allow a large number of bonsai to be displayed in a temporary exhibition format, typically indoors, as would be seen in a bonsai design competition. To allow many trees to be located close together, exhibition displays often use a sequence of small alcoves, each containing one pot and its bonsai contents. The walls or dividers between the alcoves make it easier to view only one bonsai at a time. The back of the alcove is a neutral color and pattern to avoid distracting the viewer's eye. The bonsai pot is almost always placed on a formal stand, of a size and design selected to complement the bonsai and its pot.
Indoors, a formal bonsai display is arranged to represent a landscape, and traditionally consists of the featured bonsai tree in an appropriate pot atop a wooden stand, along with a shitakusa (companion plant) representing the foreground, and a hanging scroll representing the background. These three elements are chosen to complement each other and evoke a particular season, and are composed asymmetrically to mimic nature. When displayed inside a traditional Japanese home, a formal bonsai display will often be placed within the home's tokonoma or formal display alcove. An indoor display is usually very temporary, lasting a day or two, as most bonsai are intolerant of indoor conditions and lose vigor rapidly within the house.
A variety of informal containers may house the bonsai during its development, and even trees that have been formally planted in a bonsai pot may be returned to growing boxes from time to time. A large growing box can house several bonsai and provide a great volume of soil per tree to encourage root growth. A training box will have a single specimen, and a smaller volume of soil that helps condition the bonsai to the eventual size and shape of the formal bonsai container. There are no aesthetic guidelines for these development containers, and they may be of any material, size, and shape that suit the grower.
Completed trees are grown in formal bonsai containers. These containers are usually ceramic pots, which come in a variety of shapes and colors and may be glazed or unglazed. Unlike many common plant containers, bonsai pots have drainage holes in the bottom surface to complement fast-draining bonsai soil, allowing excess water to escape the pot. Growers cover the holes with a screening to prevent soil from falling out and to hinder pests from entering the pots from below. Pots usually have vertical sides, so that the tree's root mass can easily be removed for inspection, pruning, and replanting, although this is a practical consideration and other container shapes are acceptable.
There are alternatives to the conventional ceramic pot. Multi-tree bonsai may be created atop a fairly flat slab of rock, with the soil mounded above the rock surface and the trees planted within the raised soil. In recent times, bonsai creators have also begun to fabricate rock-like slabs from raw materials including concrete and glass-reinforced plastic. Such constructed surfaces can be made much lighter than solid rock, can include depressions or pockets for additional soil, and can be designed for drainage of water, all characteristics difficult to achieve with solid rock slabs. Other unconventional containers can also be used, but in formal bonsai display and competitions in Japan, the ceramic bonsai pot is the most common container.
For bonsai being shown formally in their completed state, pot shape, color, and size are chosen to complement the tree as a picture frame is chosen to complement a painting. In general, containers with straight sides and sharp corners are used for formally shaped plants, while oval or round containers are used for plants with informal designs. Many aesthetic guidelines affect the selection of pot finish and color. For example, evergreen bonsai are often placed in unglazed pots, while deciduous trees usually appear in glazed pots. Pots are also distinguished by their size. The overall design of the bonsai tree, the thickness of its trunk, and its height are considered when determining the size of a suitable pot.
Some pots are highly collectible, like ancient Chinese or Japanese pots made in regions with experienced pot makers such as Tokoname, Japan or Yixing, China. Today many potters worldwide produce pots for bonsai.
Bonsai styles 
The Japanese tradition describes bonsai tree designs using a set of commonly understood, named styles. The most common styles include formal upright, informal upright, slanting, semi-cascade, cascade, raft, literati, and group/forest. Less common forms include windswept, weeping, split-trunk, and driftwood styles. These terms are not mutually exclusive, and a single bonsai specimen can exhibit more than one style characteristic. When a bonsai specimen falls into multiple style categories, the common practice is to describe it by the dominant or most striking characteristic.
A frequently used set of styles describe the orientation of the bonsai tree's main trunk. Different terms are used for a tree with its apex directly over the center of the trunk's entry into the soil, slightly to the side of that center, deeply inclined to one side, and inclined below the point at which the trunk of the bonsai enters the soil.
- Formal upright or chokkan style trees are characterized by a straight, upright, tapering trunk. Branches progress regularly from the thickest and broadest at the bottom to the finest and shortest at the top.
- Informal upright or moyogi trees incorporate visible curves in trunk and branches, but the apex of the informal upright is located directly above the trunk's entry into the soil line.
- Slant-style or shakan bonsai possess straight trunks like those of bonsai grown in the formal upright style. However, the slant style trunk emerges from the soil at an angle, and the apex of the bonsai will be located to the left or right of the root base.
- Cascade-style or kengai specimens are modeled after trees that grow over water or down the sides of mountains. The apex (tip of the tree) in the semi-cascade-style or han kengai bonsai extend just at or beneath the lip of the bonsai pot; the apex of a (full) cascade style falls below the base of the pot.
- Shari or sharimiki style involves portraying a tree in its struggle to live while a significant part of its trunk is bare of bark.
Although most bonsai trees are planted directly into the soil, there are styles describing trees planted on rock.
- Root-over-rock or sekijoju is a style in which the roots of the tree are wrapped around a rock, entering the soil at the base of the rock.
- Growing-in-a-rock or ishizuke style means the roots of the tree are growing in soil contained within the cracks and holes of the rock.
While the majority of bonsai specimens feature a single tree, there are well-established style categories for specimens with multiple trunks.
- Forest (or group) or yose ue style comprises a planting of several or many trees of one species, typically an odd number, in a bonsai pot.
- Multi-trunk or ikadabuki style has all the trunks growing out of one spot with one root system, and is actually a single tree.
- Raft-style or netsuranari bonsai mimic a natural phenomenon that occurs when a tree topples onto its side, for example, from erosion or another natural force. Branches along the top side of the trunk continue to grow as a group of new trunks.
Other styles 
A few styles do not fit into the preceding categories. These include:
- Literati or bunjin-gi style is characterized by a generally bare trunk line, with branches reduced to a minimum, and foliage placed toward the top of a long, often contorted trunk.
- Broom or hokidachi style is employed for trees with fine branching, like elms. The trunk is straight and branches out in all directions about 1/3 of the way up the entire height of the tree. The branches and leaves form a ball-shaped crown.
- Windswept or fukinagashi style describes a tree that appears to be affected by strong winds blowing continuously from one direction, as might shape a tree atop a mountain ridge or on an exposed shoreline.
Size classifications 
Japanese bonsai exhibitions and catalogs frequently refer to the size of individual bonsai specimens by assigning them to size classes (see table below). Not all sources agree on the exact sizes or names for these size ranges, but the concept of the ranges is well-established and useful to both the cultivation and the aesthetic understanding of the trees. A photograph of a bonsai may not give the viewer an accurate impression of the tree's real size, so printed documents may complement a photograph by naming the bonsai's size class. The size class implies the height and weight of the tree in its container.
In the very largest size ranges, a recognized Japanese practice is to name the trees "two-handed", "four-handed", and so on, based on the number of men required to move the tree and pot. These trees will have dozens of branches and can closely simulate a full-size tree. The very largest size, called "imperial", is named after the enormous potted trees of Japan's Imperial Palace.
At the other end of the size spectrum, there are a number of specific techniques and styles associated solely with the smallest common sizes, shohin and shito. These techniques take advantage of the bonsai's minute dimensions and compensate for the limited number of branches and leaves that can appear on a tree this small.
|Common names for bonsai size classes|
|Common name||Size class||Tree Height|
|Imperial bonsai||Eight-handed||60–80 in (152–203 cm)|
|Hachi-uye||Six-handed||40–60 in (102–152 cm)|
|Dai||Four-handed||30–48 in (76–122 cm)|
|Omono||Four-handed||30–48 in (76–122 cm)|
|Common name||Size class||Tree Height|
|Chiu||Two-handed||16–36 in (41–91 cm)|
|Chumono||Two-handed||16–36 in (41–91 cm)|
|Katade-mochi||One-handed||10–18 in (25–46 cm)|
|Common name||Size class||Tree Height|
|Komono||One-handed||6–10 in (15–25 cm)|
|Mame||One-handed||5–8 in (13–20 cm)|
|Shohin||Palm size||2–6 in (5–15 cm)|
|Shito||Fingertip size||2–4 in (5–10 cm)|
|Keshitsubo||Poppy-seed size||1–3 in (3–8 cm)|
Indoor bonsai 
The Japanese tradition of bonsai does not include indoor bonsai, and bonsai appearing at Japanese exhibitions or in catalogs have been grown outdoors for their entire lives. In less-traditional settings, including climates more severe than Japan's, indoor bonsai may appear in the form of potted trees cultivated for the indoor environment.
Traditionally, bonsai are temperate climate trees grown outdoors in containers. Kept in the artificial environment of a home, these trees weaken and die. But a number of tropical and sub-tropical tree species will survive and grow indoors. Some of these are suited to bonsai aesthetics and can be shaped much as traditional outdoor bonsai are.
See also 
- Bonkei – Japanese dry tray landscapes
- Bonsai aesthetics – aesthetics of Japanese tradition in bonsai
- Bonsai cultivation and care – cultivation and care of small, container-grown trees
- Bonsai styles – conventional styles in the Japanese tradition
- Deadwood bonsai techniques – description of deadwood techniques and effects in small trees
- Indoor bonsai – cultivation and care of trees grown indoors in containers
- List of bonsai on stamps
- List of species used in bonsai
- Mambonsai – pop culture twist on bonsai
- Penjing – Chinese precursor to bonsai
- Saikei – tray gardens using bonsai
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- National Bonsai & Penjing Museum - U.S. National Arboretum, Washington, DC
- The Art of Bonsai Project - galleries to show bonsai variations