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.
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.
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.
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.
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.
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
Multi-trunk or ikadabuki style has all the trunks growing out of one spot with one root system, and is actually a single tree.