Decandling Japanese Black Pine

This Japanese black pine came into my possession in 2003. It is probably about 60 years old. It is a mature specimen with a great deal of charm. Trained from seed for bonsai, it has a remarkable nebari and graceful, flowing curves.  The delicately fragile, flaky bark fully expresses its age. This tree's owner neglected proper decandling techniques for several years, allowing it to become very leggy. It was originally much taller than this, and was cut off where you see it now, about 18 months ago.

Since Japanese black pine will not back-bud on wood older than about ten years, future work for this tree includes grafting new buds in the interior of the tree where needed, as well as to remake the crown to show the flattened dome shape of mature Japanese black pines. You can see the first successful graft surrounded by the remains of the plastic bag used to keep moisture around the new graft. This was one of four grafts attempted. While this is not a great result, it was the first attempt I have ever made at grafting pine. You can see at the left, the leggy nature of the branches. This is the topmost branch with the base of the graft on the next lower branch at the center top of the photo.

Decandling step by step

Before proceeding, let me say that there are dozens of techniques and variations of methods of training Japanese black pines. Each tree must be treated individually according to its current stage of development and health. That being said, the multitude of articles on black pines can be confusing if one does not realize that each article is treating a specific tree and proceeding to generalize. I hope to present a simplified overview by using this older tree.

Why would we decandle Japanese black pines? There are several reasons, the least or last of which is achieving short needles. Decandling also provides short internodes and better back budding for ramification. It makes the branch more dense and compact, and it eliminates the long neck seen on the larger candles after they open to new needles. It also serves to keep the smaller branches from thickening and becoming coarse. By keeping them small, we provide great delicacy and superior scale. There are many ways and techniques to decandling Japanese black pines, but we will focus on only two.

The first and most important point is that the tree should be very strong and in excellent health. An old school method to produce short needles was to withhold water and fertilizer as much as possible from the tree in spring. This was dangerous and hard on the trees, weakening them considerably. A better way is to strengthen the tree and decandle it.

As soon as the buds begin to swell in early spring, fertilize the tree heavily with organic fertilizer. It is essential that you have a free-draining soil mix with no organic material in it, so that when you change the fertilizing schedule, the tree responds immediately. As soon as you begin decandling the Japanese black pine, remove all the fertilizer, and do not fertilize until the new needles from the second budding begin to harden off. Then fertilize moderately until fall. This technique provides plenty of strength for the second budding, but requires the tree to rely on its small reserves to produce the new needles. The new growth will be much smaller and more compact.

For New Black Pines in Training

To develop branches that still need to grow and ramify as they do so, the simplest technique is to group the candles into three groups by strength: small, medium, and large. Only cut the largest strong exterior candles at the base. This will strengthen the interior buds and induce ramification. For a branch that needs some more length, only remove half of the terminal candle on this branch. New buds will form farther out on the terminus.

To Refine a More Developed Tree

This is also used for trees to be shown in winter of the coming year. Divide the candles into four groups (very small, small, medium, and large.) Do not touch the "very small" candles. Cut the "small" candles first. Ten days (or so) later, cut the medium candles, and ten days later, the largest candles.

It is crucial that the candles be cut perpendicular to the growth of the candle so that buds that emerge are as close to the same size as possible. It is also essential not to leave any of the base of the candle (which steals energy fro the tree) or any portion of the candles that have needles (which allows buds to develop at the end of the stub.)

On the right you can see all of the "medium" candles removed from this tree. Notice how similar in size they all are. This tree is older and thus has less differentiation in candle size than younger trees. There are far fewer "large," "small," and "very small" candles.

An alternative method allows us to decandle an entire tree in one day, by thinning some remaining needles. Leave five pairs of needles where the "large" candles were removed, six pairs for the "medium," and seven pairs from the "small." These numbers are relative based on the strength of the tree. Leave more on a weaker tree.

Why Cut the Smaller Before the Larger?

As the second budding begins to appear, the longer the bud has to develop, the stronger and larger it will become. There are more reserves to feed it and a longer season in which to grow. Therefore we allow an advantage to the weaker buds by letting them get a head start. By the time the strongest candles are removed, there is a disadvantage. The result is that the buds will be much closer in strength as the reach maturity. Next year there will be far less difference in the strength of the buds.

Here is an example of a "very small" candle. It only sports about three pairs of needles. As the tree continues to grow, this candle will become stronger and offer better growth next season.

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