This weekend we did a little bit of spring cleaning on the dormant hardy bonsai. Japanese Maples only push growth from their internodes. That means when you prune them back, the remaining branch will die back to its closest internode, where new buds will break. This die-back doesn’t hurt the tree, but it can look a bit unsightly. It’s very predictable behavior, and is the reason why tightly-spaced internodes are desirable.
We trimmed off the dead stubs now that the die-back has finished. We also cut back the strongest growth from last year. Japanese Maples, like many trees, have apical dominance. This means they tend to focus their growth on the top of the tree, and is an evolutionary adaptation to having to compete for light. In bonsai this means that, unless the strong top growth is removed, the tree will continue to put its energy into those few large shoots, allowing the finer growth to die. By removing the dominant growth, the hormonal signal that prevents back buds from breaking is cut off, and the tree will put out lots of new growth on old wood.
Additionally, last year’s leaves were removed, as well as any dead branches. This allows more light to reach dormant buds, encouraging them to break.