A bonsai is distinct from other plants mainly by virtue of its tree-like shape and appearance. It should firstly have the common attributes of its bigger counterparts in nature. Bonsai are differentiated from ordinarily potted plants because to all intents and purposes they look like full grown trees, albeit on a miniature scale.
But to look like a tree, a bonsai should have the following characteristics of a tree –1) it should have a tapering trunk line;2) an abundance of branches reaching out in all directions; 3) a good spread of roots emerging from the base at the level of the soil disappearing into the soil gradually so as to denote stability and agedness; 4) a tree as natural looking as possible with reference to its species; and 5) a pot which is in aesthetic and visual proportion to the tree, neither too big nor too small, both together forming a harmonious unity.
The branches too should have a pattern: the first branch should emerge from about 1/3 rd of the trees height above the base, the second branch should emerge from the opposite side of the trunk but slightly from a level higher than the first branch,
the third branch again from the side of the trunk opposite the second branch; a branch growing from the back of the trunk away from the front (somewhere between the first and third branches) to give a third dimension to the tree. All other branches would then follow this pattern each emerging from a higher point on the trunk, the entire branch arrangement rising in a gentle spiral up the trunk. The branches, as they emerge from the trunk should reduce in thickness, length and development from the lowest to the topmost branch.
All the attributes mentioned above are equally applicable to bonsai created from plant species from the temperate as well as the tropical climates. However, most tropical plant species, because they have virtually three seasons per year to grow in, have a somewhat faster rate of growth then the temperate plant species which, in comparison, have only one growing season per year, Consequently, tropical plants most times do not have a triangular outline but have a more rounded appearance, with the branch lengths somewhat more extended than temperate climate trees, particularly the ficus family which also feature aerial roots which enhance the appearance of branch spread. The style classification is therefore not as rigid as they are for temperate plants.
There are things which are to be avoided in a bonsai design:-
Branches should not cross each other. They should not face in the direction of the front, i.e., the best viewing side of the bonsai.
Branches should not emerge from opposite sides of the trunk from exactly the same point on the trunk (called Bar branches).
Taper should be uniform, i.e., there should not be any reverse taper.
Extreme distortion of trunk or branches is deemed to be unnatural and therefore avoided.