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Cultivation and Care

legacy-bonsai-trees-cultivation-tools-lessons-teaching-ownership-care-products-pots-plants-kzn-durban-south-africa-pruningBonsai 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
  • 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.

cultivation-care-bonsai-trees-cultivation-tools-lessons-teaching-ownership-care-products-pots-plants-kzn-durban-south-africa-pruning-2Techniques

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 such as jin and shari simulate age and maturity in a bonsai.

Care

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 of a larger 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 vigor 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 species-dependent when the bonsai is kept outdoors as different species require different light conditions. It is important to note that few of the traditional bonsai species can survive inside a typical house, due to the usually dry indoor climate.

cultivation-care-bonsai-trees-cultivation-tools-lessons-teaching-ownership-care-products-pots-plants-kzn-durban-south-africa-pruning-3Aesthetics

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.

Display

A Seiju elm bonsai on display with a shitakusa of miniature hosta and a hanging scroll.

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. Noted bonsai writer 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”.

cultivation-care-bonsai-trees-cultivation-tools-lessons-teaching-ownership-care-products-pots-plants-kzn-durban-south-africa-pruning-5For 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 many 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. 

Containers

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.

cultivation-care-bonsai-trees-cultivation-tools-lessons-teaching-ownership-care-products-pots-plants-kzn-durban-south-africa-pruning-4Bonsai 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 describes 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 (直幹) 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 (模様木) 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 (斜幹) 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 (懸崖) 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 (半懸崖) 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.

A number of styles describe the trunk shape and bark finish. For example, the deadwood bonsai styles identify trees with prominent dead branches or trunk scarring.

  • Shari or sharimiki (舎利幹) 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 (石上樹) 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 or ishitsuki (石付) 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 (寄せ植え) style comprises a planting of several or many trees of one species, typically an odd number, in a bonsai pot.
  • Multi-trunk styles like sokan and sankan have all the trunks growing out of one spot with one root system, so the bonsai is actually a single tree.
  • Raft-style or ikadabuki (筏吹き) 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 (文人木) 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 (箒立ち) style is employed for trees with fine branching, like elms. The trunk is straight and branches out in all directions about ⅓ of the way up the entire height of the tree. The branches and leaves form a ball-shaped crown.

Windswept or fukinagashi (吹き流し) 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, mame 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
Large bonsai
Common name Size class Tree Height
Imperial bonsai Eight-handed 152–203 cm (60–80 in)
Hachi-uye Six-handed 102–152 cm (40–60 in)
Dai Four-handed 76–122 cm (30–48 in)
Omono Four-handed 76–122 cm (30–48 in)
Medium-size bonsai
Common name Size class Tree Height
Chiu Two-handed 41–91 cm (16–36 in)
Chumono Two-handed 41–91 cm (16–36 in)
Katade-mochi One-handed 25–46 cm (10–18 in)
Miniature bonsai
Common name Size class Tree Height
Komono One-handed 15–25 cm (6–10 in)
Shohin One-handed 13–20 cm (5–8 in)
Mame Palm size 5–15 cm (2–6 in)
Shito Fingertip size 5–10 cm (2–4 in)
Keshitsubo Poppy-seed size 3–8 cm (1–3 in)