Decandling a Japanese Black Pine is one of the techniques that allows for long term containment of established bonsai and establishment of younger trees as bonsai. The process of removing all the spring growth is well-documented and there are multiple techniques that are used by different people to good effect. Much of bonsai learning comes from exposure to articles originally published in Japan or heavily influenced by Japanese bonsai and because of that much of the information on the topic is aimed squarely at trees that are actually quite rare in the United States. How many full Japanese Black pine were in the last exhibit that you visited in the US?
Whether or not to decandle a black pine or whether to partially decandle it is much less frequently addressed in articles. In the US bonsai scene most black pine are in development stages so thorough decandling every year is not always the right answer if you desire the most expeditious development. Analyzing your goals for a particular tree will inform your decisions on whether or not to decandle the tree. Here are some examples of decandling that I performed (or didn’t) this year.
For trees that are in development ask yourself – will decandling further your design goals? Or will it just slow down the process of getting the tree to maturity? Selectively not decandling can encourage weaker branches to become the stronger parts of the tree. Any branch on an established mature specimen that begins to weaken can be left to grow while the other branches are decandled in summer. Selected branches on trees in development can be left to grow to create branch or trunk extensions or to increase the vigor of a particular part of the tree. Use critical thinking and horticultural analysis to help in your decisions.