how do i know the age of a bonsai?
the only certain way to control the true age of a bonsai is to cut the stem and count the wooden rings that have formed there; clear that this method, in addition to destroying your bonsai, is not so simple, since the growth rings of a bonsai are very thin, and it is difficult, however, to practice this thing even on large trees, unless you know the technique and knowing where to look.
It is therefore quite impossible to attribute an age to a bonsai, even when the selling price is very high, and would be motivated only by a truthful declaration on the real age of the small tree. A method could be to get to know someone who assures us that he was present at the time of sowing the young seedling, but also here, except that some bonsai are sold with declarations that speak of tens of years (and therefore, it is difficult to find a friendly octogenarian who confirms the date of birth of a tree, and who remembers that day), often bonsai do not come from seed, but from layering or cuttings. In the case of layering, it is often a technique that is used to remove even large branches of trees already grown, which are then cultivated as real trees; a skilled bonsaist could make a layering similar to an ancient tree in months, not years.
It is clear that everything is complicated by the fact that bonsai cultivation aims to give an adult and ancient look to trees, therefore it becomes very difficult, even for an expert eye, to decide and what is the true age of a bonsai, managing to understand which are modifications due to the age of the tree, and which are modifications induced by man, with bonsai techniques, and sometimes with illusory and almost fraudulent techniques.