In a continuation of our growing bonsai trunks series, now we discuss the method known as the sacrifice branch technique. This is a good method for all species. However, as species that do not backbud easily are less suitable for the previously explained cut-and-grow or the cut-and-grow-and-cut techniques, this is particularly usefull for pines etc.
The basic idea of this method is very simple: Allow a side-branch to grow out while keeping the rest of the plant under control. The side-branch will create a quick thickening of the trunk.
How to grow sacrifice branches
Any side-branch on your tree can be used as sacrifice branch. When selecting which branch you want to grow out, keep in mind that you will create a branch that is very thick: After removing this branch, a scar will remain. For several years you will need to work on closing the wound in the bark. So ideally you pick a branch in a spot on the back of the tree, or in the bend og the trunk. Wire this branch sideways a little, so that there is a straigh angle between the branch and the trunk. This will do two things: The attachment to the trunk will be as small as possible later on, and the branch will move away from the trunk as quick as possible.
As the branch grows, it will add girth to the trunk below the attachment point. Everything above the branch will not get thicker as a result of the sacrifice branch. Therefor this is an ideal way to increase taper: Select a branch halfway up the trunk, and you will thicken the lower half, leaving the upper half alone. Also, it may be used to correct invers taper problems: By letting sacrifica branches grow out at strategic spots, local lin areas may be assisted in getting thicker.
In order to avoid that all the other branches die, it is important to allow for some growth on all the other branches. So let the branches grow some 4 branches, and then trim back to one leaf. Also, ensure that the secrifice branch does not shade the branches directly around it. This can be assisted by removing floiage and smaller branches in the first 30cm or so of the sacrifice branch (Naturally depending on the size of your bonsai).
Now just let the branch grow, untill the girth you want is reached. Then cut the branch flush with the trunk using concave cutters. By letting the tree grow ‘wild’ for a season afterwards, you can assist in the healing of the resulting wound.
Multiple sacrifice branches
When letting multiple branches in succession grow out, you can abtain a smoother taper in the trunk by letting branches grow in multiple heights along the trunk. For the best results, you start with branches high in the canopy, moving down as you grow more branches. This gives the best taper. Is also is the worst way for healing wounds (With growth in girth you will also close wounds on the trunk.). In order to assist in healing the wounds, you can choose to grow a few smaller sacrifice branches in the canopy. Therse will help to heal wounds all over the trunk.
How big you want a branch to grow, is a question of personal taste. On the one hand: A big branch gets bigger very quickly. So leaving a branch for several years and growing them several meters long may be the quickest way to increase girth (This is often done for pines that do not easily create new side-branches). It does however create bigger cut marks that heal slowly. Creating several sacrificy branches which are for instance cut off each year is slower. It does however leave the tree with smaller cut marks, which heal much quicker and leave a smaller scar. The age-old choice between speed and beauty.
- Sacrifice branches assist in growing nicely tapered trunks
- When growing multiple sacrificy branches, start high up in the tree, moving down
- Let the branches grow untill you reacht the girth you want (This may be several meters tall in some cases!)
- To close the wounds, grow sacrifice branches high in the tree