There may be a reason that many people who are interested in bonsai have no interest in growing bonsai stock. For me the two things are one and the same. Among other goals, I want to grow a bonsai from start to maturity and see how well I can do it. My original batch of black pines has been scattering for a while now in terms of progress; while some trees are nearing what I consider a bonsai, others are still firmly in the stock-growing phase. Smaller trees are faster to grow because fewer years are required to fatten the trunk to a good size proportional to the height of the tree. The trees that have the longest to go yet are the ones that will be medium or large-size trees in the end.
While I had originally thought that the sacrifice branches on these trees would just run on until the trunks got to the size I wanted, I have since had to revise that plan. The balance between the branching that will be used for the final design and the sacrifice branch has to be maintained; so at times I have to reduce the sacrifice branch, either by removing the central strong leader, or by removing side branching. If left unchecked, the sacrifice branch will both shade out the lower branching and also weaken it by hormone inhibition.
Practical considerations also must be taken into account. For ground growing, like that done by Chris Kirk of Telperion Farms, the sacrifice can be allowed to grow quite tall because the tree is unlikely to blow over. Instead of removing the central leader you can reduce the top by removing the side branches. However, for container growing it is impractical to allow the sacrifice to continue to get taller and taller; eventually the tree will tip over even in a gentle breeze. For my 2006 batch of Japanese Black Pines I had already removed the central leader once – back in 2011 I got so frustrated with them all blowing over in the Santa Ana winds that I topped all of them. This slows the wood production but increases the vigor of the smaller branches that are eventually more important.
Below is a photo that shows multiple years of allowing the sacrifice to grow while removing the side branching. Does this optimize the balance of wood production and light to the smaller branches below? There are as many ways to make a tree as there are trees, but this seems to be a method that gives good results.
In some cases it’s a better idea to remove the central leader, particularly if there are more than one very strong upward shoots. In the case of the tree below I had allowed it to grow without reduction for a few years and the result has been that the lower branching is too weak to decandle. Without decandling the branching eventually will become too long to use for bonsai. Before this happens I need to remove the sacrifice to reduce the hormone inhibition and encourage the lower branching.
You need a sacrifice branch to create the wood that will give your tree good proportion. But, you also need to control the tree to make sure it doesn’t escape from your intentions. I reduced these trees in the middle of the growing season both to take advantage of the spring wood production and to allow the trees to respond to the cuts prior to the end of the season.
If a sacrifice is not properly managed it will become the tree instead of the tool that creates the tree.