The second essential element in bonsai is the trunk, or Kokejun. A trunk should taper to the top and it also determines the movement of the tree. A bonsai can be dynamic or static, but it must always be alive, natural, and non-artificial. By examining the trunk you can classify the various bonsai styles, which are derived from nature.
The positions in which the apex, trunk and nebari are held and the way each interacts with the other will decide which style of bonsai they are. The diagrams above show the two basic styles — formal or informal.
Formal style, Chokkan
In the formal style there are a great number of branches distributed all over the trunk. These can start from very low down.
Informal style, Moyogi
With a curved trunk we have the famous moyogi. The curves are the style’s most beautiful quality. It is necessary only to keep the few longer and stronger branches on the outside of the curve.
Slanting style, Shakan
When the pinnacle of the apex is on the right or left of centre to the nebari the tree is known as the slanting style, otherwise called shakan. The branches in this style are weighted to the direction in which the tree leans. These branches emerge from the outside of the curves.
Cascade style, Kengai
In extreme cases where the pinacle of the apex leans outside the pot, with branches that hang down towards the base, we arrive at the cascade style or kengai. In this style it’s almost true to say that there is not one apex, but two: the one at the top, the other at the base right at the tip of the cascade. These two apices must have the same movement. In other words they will both move either to the right or to the left.
Trees with vertical trunks
Tree with straight trunk
Trunk with curves
Trees with slanting trunks
Slanted or Shakan
Cascade or kengai
Examples of a good trunk
Taper and sharp angles will improve even a very tormented and artificial trunk.