How trees grow
Before delving into pruning techniques, it's beneficial to grasp some fundamental knowledge about how trees grow. This understanding will help us effectively prune bonsai trees.
Trees naturally exhibit apical dominance, meaning that the central stem of the plant grows more vigorously than its side branches. For instance, on a branch, the main stem of the branch dominates over its smaller twigs. This innate mechanism enables trees to grow taller, ensuring they are not overshadowed by competing trees. However, this growth pattern leads to the eventual death of inner and lower branches while causing the top branches to become disproportionately large, which is undesirable in bonsai aesthetics.
By comprehending trees' natural growth patterns, we can employ pruning techniques to counteract apical dominance. Since dominant growth occurs in a tree's central stems, we focus on pruning the top and outer parts more extensively. This redirection of growth encourages the development of inner and lower branches, granting us control over the tree's growth and design.
There are two forms of pruning in bonsai: Bonsai maintenance pruning and Structural Bonsai pruning.
Bonsai Maintenance Pruning
The purpose of maintenance pruning is to preserve and refine the shape of a bonsai tree. As mentioned earlier, trees tend to concentrate their growth on the top and outer parts of their branches. Therefore, it is crucial to regularly prune these areas to stimulate growth closer to the inner parts of the tree.
When to Prune Bonsai?
Maintenance pruning can be performed throughout the growing season, typically from early spring to late fall for outdoor bonsai. Indoor bonsai can be pruned year-round.
How to Prune?
Maintenance pruning involves trimming branches and shoots that have exceeded the desired canopy shape using twig shears or regular cutters. Utilizing proper bonsai tools is highly recommended. Don't hesitate to prune your bonsai regularly, as it is essential to encourage even growth distribution and the development of dense foliage. For most trees, pruning two to four times a year is recommended. If you are new to bonsai, our online bonsai course specifically designed for beginners covers the topic of bonsai pruning.
Pine trees and certain conifers should be pinched by hand rather than cut with scissors. Pruning certain conifer species with scissors or shears can result in browning and death of the foliage at the cut area. To prevent this, gently hold the tip of the shoot between your thumb and index finger and carefully pull it away. The shoot will naturally snap at its weakest point, avoiding browning or dead ends. Different species require specific pruning and pinching techniques, and some may even benefit from a combination of both methods.
Another technique used in bonsai pruning is defoliation, which involves removing leaves from deciduous or broadleaf evergreen trees during the summer to stimulate the growth of new leaves. This method is employed to reduce leaf size and enhance ramification (branching).
Structural Bonsai Pruning
Shaping a bonsai tree often involves the pruning of larger branches. Determining which branches to keep and which ones to remove can be a challenging decision. This is because it is an irreversible action that will significantly impact the tree's overall appearance.
When to Prune?
Generally, the optimal time for structural pruning is in early spring or, in some cases, late autumn, just before or after the growing season. The specific timing varies depending on the tree species. You can find species-specific information in the tree species section, as different trees, such as a Ficus bonsai or a Juniper bonsai, have different requirements.
How to Prune a Bonsai?
Position your tree on a table at eye level. Begin by removing any dead branches from the tree. Once that is done, carefully examine your tree and determine which branches need to be removed to achieve your desired design. While we provide some guidelines in the accompanying image, designing your tree is a creative process that is not strictly governed by rules.
Pruning a Bonsai tree illustration
Pruning thick branches can often result in unsightly scars, but using special concave cutters can significantly reduce the scarring effect. We recommend applying cut paste, which can be found at most online bonsai shops, to seal large wounds. This paste helps protect the wounds from infections and promotes faster healing of the tree. Once again, using the appropriate bonsai tools is crucial for achieving optimal results.
A healthy tree can generally handle the pruning of up to one-third of its foliage without issue. Some suggest cutting or removing an equal percentage of roots after styling a tree. However, most experts advise performing only one significant maintenance task at a time or even once a year. For example, if you perform structural pruning in the spring, it is advisable to wait until the following spring for any repotting or root pruning, allowing the tree to fully recover from the structural pruning.