In any endeavor, there are purists, assholes and assholish purists, i.e. snobs. No doubt in bonsai circles is no shortage of such people too. I have not met any because I am not involved in any society. I have zero contact with other bonsaists and I like it that way.
I am of the opinion that if it looks like a tree and is grown in a pot, then it is a bonsai. And if it makes the owner happy and the tree is healthy, then that is all that is necessary and it is nobody else’s business to give unsolicited advice on how the tree should look.
However, that does not mean that there are no recommendations that are pertinent for any beginner regarding the style, size, and composition of their first bonsai tree.
First, let’s talk about size. Bonsai come in sizes from just a few cms to several decimeters or even over 1 m tall. And here come in play two factors – the space you have available and your physical strength. Your tree must have enough space to grow in height and width as well, and it must get enough light to thrive. For outside trees, this is not usually a problem, but for indoor, the tree(s) container(s) should be of such a size that you can put them on your windowsill diagonally and the tree(s) should not be higher than about half of the window. That way you can turn them 90° twice a week to achieve even growth and they will get enough light.
And in regard to strength, square-cube law comes into play, I learned this the hard way. When you double the size of a tree and its pot with equal proportions, the weight increases eight-times. A pot that is visually just slightly bigger can become deceptively heavier and it can happen that the tree is unmanageable without help. Trees at circa 50 cm are a big handful for a single person and anything bigger than that might need an extra hand. But they look soooo damned good and impressive…
As for style, there is a whole Japanese terminology that I have never bothered to not forget. Sure, I have it in a book somewhere and I read up on it thoroughly, but it is not useful to me now. That is not to say that it is not useful at all. As all terminology, its purpose is descriptive, in order to allow better communication. And since I do not communicate about my trees too often, I do not need to remember it. If I need to describe my trees sometime, I can always look it up.
The word “descriptive” is key here. A bonsai is a tree in a pot by definition, so the only criterion here is it should look like a tree. My advice to a beginner would, therefore, be to try and shape the plant you have to look like a tree – any tree – and not try and shoehorn it into some specific style.
Both size and style are to a certain extent also species-dependent. Some trees can take heavy abuse and be contorted into wild shapes, some are fragile, sensitive and brittle, some have huge leaves, some tiny etc.
Regarding composition, the usual rules of art apply. For example, the tree and its pot should fill a picture with 4:3 or 16:9 ratio, the golden ratio applies etc. Most people have an adequate aesthetic feeling to do this properly in my opinion, There are, however, several bonsai-specific rules that are important to mention.
The tree is a statue that has a front and a backside, but it is three-dimensional. So branches should point in all directions, not only to the sides. But no branches should point straight forward towards the observer, it creates an unpleasant feeling when observing the tree, it actually strains the eyes a bit.
The trees are meant to be observed with approx 1/3 of the tree at eye height- for example when they are on a windowsill, you should be appreciating them when seated. In order to achieve the best result, the tree trunk should be bent ever so slightly towards the observer. It creates an optical illusion that makes the tree appear slightly bigger than it actually is. Trees that straight create an illusion of being bent backward and that, again, is not entirely pleasant to look at.
Big wounds, if they are not part of the composition, should be hidden on the back or on the sides. Wounds, like dead branches and hollows, that are part of the composition should, of course, be visible and therefore positioned either on the front or on the sides. If wounds on the front side are not avoidable, the tree should not be displayed until they heal, but that is not a problem for me – or for a beginner.
And lastly, the pot is a part of the composition, so its shape and color should complement the tree, but it should not clash with it or compete with it. A straight-lined square pot will look strange with a tree that is all twisty-bendy, and plain brown pot will look a bit drab with a plant that has bright red leaves or flowers. When in doubt, an ordinary bowl works most of the time.
Hopefully, I have not forgotten anything important here. Next time I will maybe finally write about a concrete species and how to care for it.