One of my major interests and goals in the study of bonsai is growing a tree from start to maturity, and see how well I can do it. Over the years that I've been starting black pines from seed, I've learned a lot about growing, reducing, and removing a sacrifice branch in the development of a good bonsai tree. 

I originally thought that the sacrifice branches on these trees would just run on until the trunks got to the size I wanted. I revised that plan when I realized that to maintain the balance between the branching that I'll use for the final design and the sacrifice branch, at times I'd have to reduce the sacrifice branch, either by removing the central strong leader, or by removing side branching. If left unchecked, the sacrifice branch would both shade out the lower branching and also weaken it by hormone inhibition.

I also need to take practical considerations into account. For ground growing, 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 in 2011. While this slowed the wood production, it increased the vigor of the smaller branches that are eventually more important. 

The small branches that are being maintained for the final design on this tree are strong enough to decandle. But, the sacrifice branch also needs to be reduced or hormone inhibition and shading will make these branches too weak.

In some cases it’s a better idea to remove the central leader, particularly when there is more than one very strong upward shoot. I allowed the tree below to grow without reduction for a few years, which resulted in the lower branching being too weak to decandle. Without decandling the branching would eventually become too long to use for bonsai. I needed to remove the sacrifice before that happened to reduce the hormone inhibition and encourage the lower branching.

It took nearly ten years of growing to get this tree to be taller than me, and it will only take a two minutes to reduce the height to a more manageable level.

Using a saw I remove approximately 75% of the top branching.

Both the central leader and all it’s upper branching are gone, leaving just one strong side branch. Side note: why do I look so serious?

After reducing the tree it will be much easier to manage and the side branch on the top will become the new sacrifice.

You need a sacrifice branch to create the wood that will give your tree good proportion. 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.