The Importance of Timing in Bonsai

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There are a wide range of techniques available to the bonsai enthusiast that can help keep his/her bonsai healthy, vigorous and in shape throughout the year.
These techniques range from the straightforward but essential, such as pruning and repotting, to the more advanced such as wiring, trunk chopping or grafting.
The key to using these techniques successfully is partly due to the knowledge needed to carry them out correctly, but also very importantly, when they are carried out.

All bonsai techniques must be performed at the correct time for them to be successful. Failure to adhere to the correct timing can kill or injure bonsai and will greatly increase the possibility of the technique failing to have the desired outcome.
A technique such as repotting and root pruning is perfectly safe as long as the timing is correct; root pruning at the wrong time will kill or at very least, seriously weaken your tree.

Cyclic Timing

Almost all plants and certainly those that are used for bonsai have an annual or cyclic growth pattern.
In other words, over the course of one year, a plant will pass through a series of states and conditions that will not be repeated until the following year. These annual growth patterns are closely shaped and defined by the annual cycles of the sun, season and the weather. These annual growth patterns also subtly change according to your own climate and the weather experienced in your area in the previous weeks and months. (Tropical climates and indoor cultivation can and will interrupt or negate these seasonal variations making timing more difficult and in some cases, less important).

All bonsai techniques have recommended 'times' during the year that they can be performed. Dependent on the nature of the technique, the timing maybe described as anytime over 3 or 4 months of the growing season to as little as a 2 week window that occurs only once a year. Unless you have full understanding of the technique, the physiological reasons for the timing and an understanding of the risks of ill-timed work, always adhere strictly to the recommended timing you are given. Never be tempted to carry out ill-timed work in the belief the tree will be 'finished' more quickly; very often this results in a weak tree whose development time is greatly increased.

It should be added that it is important not to be tied to calendar dates when deciding when to repot, prune, wire or carry out any other bonsai technique.
The exact timing necessary depends on your national, local climate and the climate or conditions that your trees are subject to, the health of individual trees, and the actual species of tree. It is not unusual to have trees of the same species and same position in a garden that require repotting maybe a month apart!
For this reason you must learn to time your work according to the condition of an individual tree. For instance, repotting of a deciduous tree should be carried out as the new buds start to extend and not because some guy a continent away says to do it in February or March. Many bonsai books will give you a set date to try and adhere to. This is probably done to simplify timing explanations but it may well also cause problems with the health of your bonsai.
It maybe a harder way to learn and remember at first but by learning to react to your trees, your timing will be better. Instead of learning a calendar date, learn the signal that the tree will give you. Try to find sources that explain which signals in your trees to look for.

Recuperative Timing

The second form of timing that must be considered is recuperative timing. This is the amount of time a tree requires to recuperate or recover from work carried out on it.
When a tree is worked on there is a period of time where it is in a weakened state and/or it's resources are tied up in response to the work. During this time, additional work may reduce the already weakened tree to a state where it is unable to recover and either grows very slowly or even dies.
An example might be defoliating (removal of all the leaves in midsummer) and root pruning. Either of these techniques can be carried out with great success on healthy, vigorous trees. However, defoliating a tree at midsummer that has yet to recover fully from it's spring root pruning can have a devastating effect on a bonsai.

Not allowing enough recuperative time between work is a common mistake to make, particularly for beginners. Judging the time needed to recuperate depends on many factors such as the vigour of the tree species used, the individual trees health at the time of work and the nature of the actual work that is carried out.
On a general basis, the more invasive the work, the longer a period of time is required for recovery. Recovery can be counted in days for the trimming of a vigorous tree (such as a Chinese Elm) to months for the root pruning of a weaker species or even years for trees that have been collected from the wild.

Learning how much time a tree needs in order to recover from work is difficult to generalise and comes largely with experience but is ideally learnt by studying the reaction of the tree to work and knowing when a tree is growing with renewed vigour.
A good general indicator of renewed vigour and recovery in many trees is the appearance of new shoot growth (extension) and successful hardening off of these shoots. Note that new buds and new leaves on their own are not indicative that a tree has or will recover from work that has been carried out.

A healthy nursery tree is bought during the summer and you style it immediately. Pleased with your efforts, you are unable to resist the temptation to plant it straight into a bonsai pot even though it is late Summer and your timing is wildly wrong.
The result is a tree that is too weak to respond to your styling and fails to grow for the remainder of the Summer and early Autumn, though luckily for you, it doesn't die.

The following Spring the tree starts growing, but a few branches have died back during the Winter, your styling is wrecked and the tree is still too weak to put out any new shoots. A year later, your lack of patience has resulted in a bonsai that may take another season before it actually recovers from all of your work.

With a little patience, your newly styled tree could have been allowed to recover and have been repotted just 6 months later, at the correct time, during the following Spring. This tree will have been given recuperative time after styling and repotted at its correct cyclic time. The resulting bonsai would be vigorous, suffer no dieback and be ready for further wiring and trimming within a few months. Most importantly it would be much better developed than the tree that had the ill-timed repot.

Patience is the hardest part of learning to use correct timing practises to your advantage. The temptation to plant your newly styled tree into it's first bonsai pot can be difficult to resist. However, with experience you learn that by obeying the rules of timing, your trees' progress and development will be always be much quicker.