Bonsai Glossary

Japanese volcanic clay fired at high temperature, the reference substrate for bonsai. Offers an excellent balance between water retention and root aeration. Gradually breaks down and should be renewed at each repotting.

The summit of the tree, the final terminal bud that defines the last line of the silhouette. The apex is the visual convergence point of the entire composition and must be shaped with precision.

Soft and lightweight metal wire, easy to apply and remove, ideal for wiring soft-barked species (maples, ficus, zelkovas). Less expensive than copper, recommended for beginners.

A technique for rooting a section of trunk still attached to the tree by cutting the bark and maintaining moist moss around it. Allows the creation of a new specimen with a developed nebari, or the shortening of an overly tall trunk.

Literati style — a slender, refined silhouette with a thin trunk, few branches, and foliage concentrated at the top. Inspired by the ink painting of Chinese literati (bunjin-ga), it evokes a minimalist poetry.

A mix of primarily inorganic materials (akadama, pumice, kiryu…) constituting the bonsai's growing medium. Must combine sufficient water retention with optimal drainage to prevent root asphyxiation.

Vegetative propagation by taking a segment of stem or root and rooting it separately. An economical method to multiply certain species such as Ficus or Carmona.

Sculpting dead wood (jin, shari, uro) with rotary tools or gouges to create natural textures and expressive forms. Practiced on hard-wood species such as juniper or cypress.

Formal upright style — a perfectly vertical trunk that tapers regularly from the nebari to the apex, with symmetrically arranged branches. Evokes a tall conifer of the plains, a symbol of strength and dignity.

A size category for bonsai measuring between 25 and 40 cm tall. This intermediate size is considered the most accessible — large enough to work easily, without the constraints of very small specimens.

Removal of the apex or terminal buds to stop upward growth and encourage the development of lateral branches. A structural step in building the silhouette.

Rigid and resistant metal wire, preferred for hard-barked species such as pines and junipers. Provides better long-term hold but requires more care to avoid damaging the bark.

A technique consisting of removing all leaves in early summer to trigger a second flush of finer growth with smaller leaves. Reserved for vigorous deciduous species; never practice on a weakened tree.

An acid substrate based on decomposed organic matter, used specifically for acid-loving species (azaleas, rhododendrons, blueberries). More organic than Japanese mineral substrates, it breaks down faster and requires more frequent repotting.

Windswept style — trunk and branches all oriented in the same direction, as though shaped by decades of prevailing winds. Creates a very dynamic and narrative composition.

Joining a scion onto a rootstock to introduce new branches at a precise location, improve ramification, or change variety. An advanced technique used notably on pines and Satsuki.

Coarse sand or quartz aggregates of 1–3 mm grain size, used as a draining component in substrate mixes. Very common in the UK and English-speaking countries. Improves drainage without retaining moisture, often combined with akadama or ericaceous compost.

Semi-cascade style — apex descending to the rim of the pot or slightly below, without passing the base of the pot. An intermediate position between the slanted style and the full cascade.

Broom style — branches all starting from the same low point on the trunk and spreading in a regular fan to form a dome-shaped silhouette. Typical of Japanese maples (Acer palmatum) displayed in winter.

Rock-planted style — tree cultivated directly in a cavity or crevice of a rock, with little or no visible substrate. Evokes a tree growing wild in a rockfall or on a cliff face.

A dead branch or crown, stripped of bark and bleached, imitating the action of lightning, frost, or time. The jin is sculpted and treated with lime sulfur to preserve it and accentuate its natural appearance.

Acidic Japanese volcanic substrate used specifically for Satsuki azaleas and all acid-loving plants. Its naturally low pH (5.5–6.5) suits species that struggle in alkaline conditions.

Cascade style — apex descending below the base of the pot, imitating a tree clinging to a rock face with branches falling toward the ground. Requires a deep pot and an elevated display stand.

Light and highly free-draining Japanese volcanic aggregate. Often mixed with akadama for Mediterranean species or pines that require a particularly lean and well-aerated substrate.

A composition of companion plants (wild grasses, bulbous plants, mosses) displayed at exhibitions alongside a bonsai to evoke its natural environment and highlight the seasons.

A calcium polysulfide solution used to bleach, harden and protect dead wood against fungi and insects. Applied with a brush to jin and shari, it gives the wood its characteristic bleached appearance.

Volcanic lava granules, very popular in France, Italy and Spain as an economical alternative to akadama. Excellent drainage, good root aeration, does not break down over time. Often used in mixes with akadama or alone for Mediterranean species.

A Japanese concept of empty space and visual silence between elements, essential to the breathing of a composition. In bonsai, ma designates the space between branches that allows the silhouette to breathe and the eye to rest.

A size category for bonsai under 15 cm. Mame are the smallest bonsai and require daily attention, as their substrate dries out very quickly.

The dynamism and visual direction of a bonsai's trunk, an essential factor in its character and personality. A tree with movement tells a story and gives the impression of having fought to survive.

Informal upright style — a slightly sinuous trunk with natural curves progressing toward an apex above the nebari. The most common and natural of styles, suited to a wide variety of species.

Exposed-roots style — the tree's roots emerge from the soil dramatically, as though the substrate had eroded over time. Gives a sense of great age and raw strength.

The network of surface roots visible at the base of the trunk. A key indicator of a bonsai's maturity — a well-spread nebari gives visual stability and a sense of age to the composition.

Deliberately maintained empty space between branches and foliage, which contributes as much to the composition as the foliage itself. Mastering negative space is the hallmark of accomplished bonsai artists.

Selective removal of certain leaves or shoots to balance vigour between strong and weak branches, without subjecting the tree to the stress of full defoliation.

A flat, horizontal mass of foliage formed by the terminal shoots of a branch. Well-defined pads, presented at distinct levels, create the characteristic three-dimensional structure of a bonsai.

Volcanic glass expanded by heat, very light and inert. A draining and aerating component used worldwide in bonsai mixes. Inexpensive and easily available, often the first mineral component used by beginners.

Manual removal of new shoots with the fingers to control vigour and encourage fine ramification. A basic technique practiced in spring on most species.

A light and porous volcanic rock widely used in France and southern Europe. Used as a drainage layer at the base of the pot or mixed with akadama. Denser and less porous than pumice, it lasts several years without degrading.

A porous volcanic rock used as a draining component in bonsai substrate mixes. pH-neutral, it improves root aeration without retaining excessive moisture.

The network of secondary and tertiary branches forming the internal structure of the silhouette. Fine, dense ramification is the result of several years of regular pinching and wiring.

Removing the tree from its pot, pruning invasive roots, and replanting in fresh substrate. Practiced every 1 to 5 years depending on species and age, it maintains the tree's vigour and controls its development.

Progressive refinement of ramification by tapering branches from the base toward the tips. Good sabaki creates a natural transition between structural branches and fine terminal twigs.

Split-trunk style — a deeply hollow, torn, or partially consumed trunk, as if struck by lightning. On the verge of survival, the tree symbolises resilience in the face of the forces of nature.

Root-over-rock style — the tree's roots embrace and descend along a rock before plunging into the substrate of a classic pot. The rock and roots form an inseparable whole.

Slanting style — trunk leaning at 45–60° from vertical, imitating a tree growing on a wind-exposed slope or cliff edge. The branches compensate for the trunk's inclination to balance the composition.

A surface of dead wood on the trunk, stripped of bark to imitate natural erosion and ageing. The shari creates a striking contrast between living wood and bleached wood, reinforcing the impression of age.

Bleached-trunk style — a large portion of the trunk stripped of bark and worked into an extensive shari, very common on junipers. The contrast between bleached dead wood and living bark creates a composition of great visual power.

A size category for bonsai measuring between 15 and 25 cm tall. Appreciated for their delicacy and manageability, shohin require very frequent watering due to the small volume of substrate.

Sphagnum moss used primarily for air layering (kept moist around the cut) and as aesthetic top-dressing. Its exceptional water-holding capacity makes it an indispensable tool for propagation techniques.

A stoneware pot produced in the city of Tokoname in Japan, the world capital of bonsai ceramics. Recognised for the quality of its clay, the fineness of its glazes, and the wall porosity that promotes root respiration.

Replacing the surface layer of substrate without removing the tree from the pot, practiced between repottings to replenish exhausted minerals and improve surface drainage.

The section of trunk between the nebari and the first branch. The tachiagari must present the tree's most significant movement and curves — it is the visual foundation of the entire composition.

A technique of attaching a living tree to a sculpted piece of dead wood to simulate a very old trunk. Popular in Japan, the term refers to the tanuki (raccoon dog) of Japanese folklore, associated with trickery and transformation.

American calcined clay, an economical alternative to akadama. Good water retention and adequate root aeration; often used as a partial substitute in substrate mixes.

A natural or sculpted hollow in the trunk, resulting from a fallen branch or an old wound. A sign of great age, the uro can be enlarged and carved to enhance the bonsai's character.

Wrapping metal wire (aluminium or copper) around branches and trunk to impose a direction and a curve. The wire must be removed before it marks the bark, generally after 3 to 6 months.

A Japanese aesthetic philosophy that values imperfection, incompleteness, and the ephemeral as sources of beauty. In bonsai, wabi-sabi translates into an appreciation of scars, knots, and the natural character of the tree.

A tree collected from the wild — mountain, cliff, moorland — and gradually adapted to container culture. Often bearing exceptional character built over decades of struggle against the elements.

Forest style — several trees of different sizes planted in the same flat pot, evoking a grove with perspective and depth. By tradition, the number of trees is always odd.