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Pruning
Tree Care

Pruning

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Hard Pruning/ Removing Branches
Pruning of branches is nearly always carried out when the trees' growth slows down in late Autumn through to Spring to avoid excessive sap-loss. When pruning in Winter it is always best to leave a small stub rather than cut back close to the trunk. Leaving a stub when pruning pines is advantageous as it leaves open the opportunity in the future of creating jins and it also allows time for the sap-flow to bypass the missing branch, reducing sap-loss through bleeding. Pruning close to the trunk and hollowing out is best carried out whilst still semi-dormant in early Spring as scars will heal quickest with the Spring growth that follows.

It is better to be conservative when hard-pruning and reducing Pines. Severe reduction without allowing for recovery time can be fatal particularly with old or large trees. Reduce large trunks and/or branches gradually over a number of seasons so that the tree is able to adjust.

Needle Plucking
Needle plucking is a very useful tool for pine maintenance. It allows air and light to penetrate the outer foliage to increase the health and vigour of inner shoots and branches. It also helps to spread energy throughout the tree in the same way that bud selection and candle pinching do.

In late Autumn or early Winter, both old and new needles are plucked according to their position on the tree. The principal behind needle plucking is that the more foliage or needles a branch has, the more vigorous it is; by reducing the amount of needles on a vigorous area of the tree (such as the apex) in comparison to the number of needles a weak area has, vigour is distributed more evenly.
Diagram showing shoots that have been needle-plucked according to their position on the tree
From left to right
Image 1: Lower or inner shoot
Image 2: Mid-level shoot
Image 3: Upper or Outer shoot

As a basic rule leave less needle-pairs on the upper shoots and more on the weaker, lower and inner shoots. Often no needles are plucked from inner shoots to preserve their vigour. The actual numbers of needles that are removed will depend on the needs and strength of the tree. With a very vigorous tree it may be possible to leave as little as 4 pairs of needles on the upper branches, 6 or 7 pairs on the mid-level branches and 8-12 on the lower branches. Base your starting number on the lowest, weakest shoots since you can only decrease strength with this technique and not increase it. Do not remove so many needles that the overall vigour of the tree or branch is lost.

Shoot Trimming and Forcing Back-Budding
To force a Pine to back-bud is difficult ordinarily. However, shoot trimming is a useful technique for trying to force back budding and generally increasing the number of buds on a tree.

All shoots should be allowed to grow unhindered throughout the growing season. In Autumn, all the current years' growth is removed leaving only the previous years needles. This will cause the tree to produce a large number of buds at branch tips and further back along the branches, sometimes even into old wood. This technique is however very stressful for the tree and should only be carried out on healthy, vigorous specimens.

Bud Selection
The development of foliage pads or branch structure on a bonsai dictates that the branch tips should fork and sub-divide into only two smaller sub-branches. As previously stated, Pine buds most often emerge in clusters or whorls at the end of branch tips. The basic rule in Bud Selection is to select two of the buds and remove the rest so that when the buds extend as shoots they form a two-pronged fork.

Selection of buds according to position on tree

From Left to Right;

Image 1: Example of a typical bud-cluster
Image 2: A cluster in a dominant area should be reduced to two weak buds
Image 3: A cluster in a weaker area should be reduced to 2 or 3 stronger buds

 

Buds continually need to be reduced to two as they appear, in Autumn and in Spring. Deciding which 2 buds in a bud cluster should be retained needs some consideration. As previously stated pines are apically dominant, upper and outer areas can (and should) be restrained by careful bud selection and elimination. Apical areas of a pine can produce 5 or more buds to a shoot terminal, by removing the largest and strongest buds and retaining the two smallest and weakest, vigour is re-directed to wards inner and lower areas of the tree. Conversely, weaker lower branches are allowed to retain their largest, most vigorous two or three buds to encourage more vigour to them. If a third bud is retained on a weak branch it can be removed at a later date when its job is done.

To encourage good branch structure and proper formation of foliage pads, whenever possible, buds that appear on the sides of a shoot should be retained rather than those than on top or below.

Extension of buds into new sub-branches

From left to right;

Image 1: Appearance of shoot tip before bud selection in Spring.
Image 2: After bud selection.
Image 3: After extension of the buds into new sub-branches in Summer. Note the appearance of a further set of buds developing at the new shoot-tips.

Candle Pinching
During the Spring, the buds that you have retained will elongate into candles, their size being in relation to each candle's individual strength and vigour. To ensure that growth extension is regulated and energy is dispersed evenly throughout the whole tree; these candles need to be pinched back. The amount that each candle is reduced depends on its position within the structure of the tree and its future purpose. After the candles have extended into new shoots and branches, it is at their tips that new buds for next year will form.

Just as in bud selection, candles growing in more vigorous areas of the tree should be reduced by far more than candles growing in weaker, inner areas. If a new branch or sub-branch is required the candle can be left unpruned to extend; however it should be noted that more of the trees energy will be directed to it at the expense of other areas. Candles left unpruned to encourage vigour in weak areas or to develop new branches can then be cut back to a desirable length once they have fully elongated and hardened, this will soon be followed by the appearance of buds at the tip.

The timing of pinching out candles will affect where the new buds that follow will form. Pinching the candles before the new needles appear will cause new needles to form at the base of the candle. Pinching the candles after the needles begin to appear and start to elongate will cause the buds that follow to form at the end of the new shoot.

Don't pinch out all the candles at once. Start pinching out the weaker areas of the tree first and finish with the strongest areas 2-3 weeks later. Generally, as a rule of thumb, candles growing in vigorous areas of a Pine should be reduced by at least 1/2 to 2/3, candles in weak areas should be reduced by no more than a 1/3.

 NEEDLE REDUCTION
It is often necessary with all but the largest Pine bonsai to reduce the length of the needles to help refine the image of the tree.
It has often been that recommended that needle reduction can be achieved by reducing the amount of water and fertiliser available to the tree during the Spring so that new needle growth is limited; literally 'starving' the tree. This is not a satisfactory technique as it entails deliberately weakening the tree and reducing its vigour for a number of weeks.

These days, there is a new technique which helps reduce the length of needles by limiting the time the tree has to grow it needles before growth slows or stops for the Winter.

Allow shoots to grow through the Spring and Summer. In mid-Summer, cut the new shoots leaving only last year's needles. Over the course of the next few weeks new buds will form; these will need to be reduced to two as outlined previously. These new buds will not develop into candles, but will sprout new needles as soon as possible. They will not have enough time in the remainder of the season to grow long resulting in a set of reduced needles.

Trimming back shoots in Summer

From left to right:

Image 1: Two candles that have been allowed to fully extend into shoots.
Image 2: After trimming back in Summer
Image 3: Resulting buds.
 

This technique should only be carried out on Pines that have an established trunk and branch structure. Using this technique will decrease the vigour of the tree and its ability to thicken up branches and trunks; needle reduction should be regarded as the last stage of developing a pine bonsai.