The short answer to this question is a simple ‘Yes’!
A bonsai tree is a normal tree that is kept small by pruning of both the tree roots and its branches, and in every other respect it is exactly the same as any other tree of its species.
If a bonsai tree was taken out of its pot and planted into the ground, and then left for 10 years, it would look exactly the same as any other tree of the same species… same height, same size leaves… same everything!
The skill in creating bonsai revolves around trimming the roots and branches so that the tree can not only be kept in a relatively small pot, but also end-up looking like a real tree in nature, but seen from a distance.
In essence the technique is just a few steps up from you trimming your garden hedge to keep it at the height you want.
Another example would be ‘Topiary’, where hedging trees are cut and trimmed to produce shapes like balls, squares, and even animals!
The Bonsai seed myth…
There is a widespread myth that bonsai are grown from ‘special bonsai seeds’ … the plain truth is that there is no such thing as a ‘special bonsai seed’!
Bonsai are grown from ordinary seeds … seeds that, if planted in the ground and left alone, would produce a ‘normal’ tree like any other in its species.
BUT… by keeping the growing tree in a relatively small pot (trimming the roots when needed) and pruning the growing tips of the tree to keep it at the size you want (and wiring branches to the shape you want the tree to take) you will end up with a tree that – in every respect – can be called a ‘Bonsai’.
Real bonsai trees can also occur in nature, for example, up on the side of a mountain where strong winds and cold winters or other rough conditions have had the effect of stunting the growth of the tree so that it is much smaller than it would be in better weather conditions. Trees like this are highly prized by bonsai enthusiasts and are called ‘Yamadori’ – essentially meaning ‘collected from nature’. Yamadori can be inches tall, or a metre+ tall, and they would take a prized place in any bonsai collection.
NOTE: Yamadori would ONLY by collected from nature if it was legally acceptable, and with any permissions needed… and – of course – only if it was possible to be taken out of the ground without the risk of the tree being damaged or killed.
Sometimes beautiful Yamadori are simply left where they are, to be admired as the wonders of nature that they are.