Pruning is an essential practice for removing unwanted branches, maintaining your bonsai form or to encourage new growth. It also helps to decongest the look of the bonsai to make sure it is proportion and realistic. Removing selected branches will open up the tree structure and provide more space for the tree to grow into – this should be done annually and can sometimes be quite significant but will be for the better of your tree.
Pruning must be undertaken at the right time of year and wounds that are created must be neat and unobtrusive to not affect the bonsai trees aesthetic, so we have put together a useful set of guidelines to help with pruning your bonsai tree.
General branch pruning is best done in autumn, while maintenance pruning should be undertaken in late winter or early spring as the tree is active and begins healing immediately. Meanwhile regenerative pruning is best done in mid-summer when the tree is growing at its fastest possible rate.
Make sure to use the correct bonsai tools to minimize damage to your bonsai tree. A concave cutter is best to leave a small indentation behind resulting in a smaller scar.
Small twigs can be cut off close to the trunk with a pair of shears, however heavier branches will require using the concave cutter. For larger, very heavy branches a saw or heavy duty secateurs/shears must be first used to remove the majority of the branch and then cleaned up using the concave cutters to remove the remaining stub.
Then pruning cuts must be sealed immediately using a paste. A putty-like substance to keep the newly cut edge moist to prevent contraction of the surrounding tissue which can produce a nasty looking scar. Preferably using Japanese cut paste is best but as an alternative children’s synthetic modeling clay mixed with a little olive oil to prevent it from hardening. Other alternatives are PVA wood glue or even bathroom mastic. The paste can then be removed once the edges of the wound have begun rolling in.
Generating New Growth
In certain situations you may want a branch to fork into multiple branches to regenerate growth in a certain area. To achieve this, cut the branch where you want it to branch out and cut straight through using a fine saw or angled cutter. Then apply Japanese cut paste to seal the wound, if you cannot use the proper compound then do not use any other alternative and leave the wound as is but protected from the sun.
New buds will then grow from the cut end and once each small branch has three or four leaves decide which new growth you want to keep and cut back any unwanted branches.
One of the most important ongoing bonsai tree care methods is maintenance pruning to keep the balance between roots and foliage while maintaining the desired aesthetic. The annual growth of the tree must be kept under control, so you have to reduce the number of outer twigs to allow enough space for the following years growth and not just nipping the tips of the new shoots. Every two to four years (depending on your bonsai trees species and size) a vigorous cut back will be required to remove quite old sections of branches to rebuild their structure.
This type of pruning is best done when your bonsai is during a resting period. For conifers this means in late autumn except for Junipers who prefer early summer. Broadleaf’s respond best to maintenance pruning in late winter.