Last year, I pruned and partially defoliated the Korean hornbeam below in early June. The timing was just about right for the work as each shoot had a moderate amount of new growth (see “Spring maintenance” for details).
This year the tree grew more vigorously – likely a result of being repotted – and was overly full by mid-May.
Korean hornbeam in spring
I knew the tree was ready for cutback and defoliation in early May, but didn’t get to the work until this week.
As I worked on the tree, I found that a number of the interior shoots were already starting to die off. Since one of my goals for this stage of development is to improve the fine branch ramification, I need to keep after the new growth on the exterior of the tree to make sure the interior branches receive enough light to maintain vigor.
After cutback and partial defoliation -18″ tall
If I’d waited until mid-June to prune, I would have lost valuable foliage in the tree’s interior.
I don’t worry about the timing as much for bonsai in earlier stages of development as they typically lack density. For these trees, I try to prune when the spring growth hardens off.
Going forward, I’ll trim or pinch new growth that extends beyond the current outline to give the interior shoots more of opportunity to gain vigor and fill in a few gaps in the tree’s silhouette.
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