The Informal Upright bonsai tree grows more or less upright, but with gentle curves in the truck. The trunk starts off at an angle and usually curves gently back and forth two or three times before it reaches the top. This is the most common style and a good style to for a bonsai beginner to start with. Informal Upright Style is suitable for most species of tree, and especially suited to deciduous trees and flowering trees like maples and elms, prunus and quince.
Slanting Style (Shakan)
As it sounds, the trunk of the Slanting Style Bonsai is slanted at an angle to the surface, as though the tree was jarred sideways by a strong gust of wind, or knocked over in landslide or by another larger tree falling onto it, or some other similar natural phenomenon. Normally with branches on both sides of the trunk.
Formal Upright Style (Chokkan)
The trunk is up-right and dead straight from bottom to top. The trunk should always have a visible taper with the widest part of the trunk at the based of the tree and supported by a suitable nebari (or surface root structure). In nature this style is quite common in trees growing in open flat ground, well protected from harsh winds and without much competition from other trees. A formal upright tree presents a picture of perfection, regal maturity and a timeless quality.
Cascade Style (Kengai)
The Cascade style is easily recognized and a very desireable style of bonsai tree. It represents a tree that is growing on a cliff top or out of the side of a cliff with branches that have cascaded below the base of the tree. This style is suitable for most species, but is particularly prevalent amongst juniper, yew, pine and other confer bonsai. It obviously takes a lot of time and work to perfect the shape and it will also need frequent retraining as the tree will always try to grow upwards where possible.
Semi-cascade Style (Han Kengai)
Like the cascade style, the tree trunk descends below the rim of the pot but it doesn't normally go any lower than the base of the pot, allowing the tree to be displayed on a table. This style represents a tree growing over riverbanks where the branches grow almost horizontally over the water surface. This style is suitable for most species, but is particularly prevalent amongst juniper, yew, pine and other confer bonsai.
Broom Style (Hokidachi)
Generally with an upright trunk, although it can have slight curves, with branches and foliage radiating outwards in the shape of a Japanese fan or an Umbrella. They are sometimes also called lollipop trees. This style can be fairly easy to create and is also very accurate to many trees in the wild. Particularly suited to Chinese Elms but can be created with most tree species.
Raft Style (Korabuki)
Raft Style imitates those trees that have fallen down but continue to grow with the branches on one side becoming like individual trees. Commonly this style is found in a Straight-line or Ikadabuki imitating a tree trunk, occasionally you see a more Sinuous Root Connected Style (Netsunagari) which imitates a connected surface root that has meandering around and sent out new branches.
Group / Forest Style (Yose)
Forest Group plantings are groups of anything more than 3 bonsai trees. Sambon-Yose (3 trees), Gohon-Yose (5 trees), Nanahon-Yose (7 trees) and Kyuhon-Yose (9 trees). Forest groups usually have odd number trees as they are thought to look better and allow for easy symmetry around a focal tree, usually the largest tree. There are two general styles of Forest Groups: Yoma-Yose Style, with trees spread out evenly around the pot or slab, and Tsukami-Yose style, with trees growing outward from the center, imitating trees on a small hill top.
Windswept Style (Fukinagashi)
Windswept bonsai trees lean heavily to one side with all branches on one side. Tree like this grow atop gusty hill sides and sea shore, where strong wind damages young shoots on the windward side, but shoots on the inland side survive and grow. Blackthorns and other prunus species make beautiful windswept specimens in the wild
Twin Trunk Style (Soju)
Any tree with two trunks from one root ball. The two trunks split just above the soil level with one usually being subservient to the other. The crown is usually formed by branches from both trunks. An alternative of Two Trunks is Sokan Style, or double trunk, where one trunk splits just above the soil line and the two branches are treated as separate trees.
Root over Rock Style (Sekijoju)
The tree grows over a rock with roots reaching down to the soil beneath the rock in search of water. This can happen in nature when roots reach over permanently wet rocks or when erosion removes a thin layer of soil. A variation of this style is “clinging-to-a-rock style” (Ishitsuki) where the tree clings to the rock surface, rather than ‘sits’ on it. Fig trees commonly cling to rocks and other trees. These styles take a long time and a lot of skill to accurately replicate.