Bonsai defoliation (leaf-cutting)
What means bonsai defoliation ?
Bonsai defoliation (or leaf cutting) is a technique of bonsai styling in which all or a large part of the leaves and all buds at the end of each shoot are removed with a sharp bonsai scissors.
After a few days (e.g. elm bonsai) or weeks (e.g. Horse chestnut) the buds of the bonsai will sprout completely new. Many "sleeping buds" are activated and the branching increases significantly. In most cases the new leaves are also much smaller.
What are sleeping buds ?
A tree competes with other plants. When a seedling grows it needs light to grow. The grasses and bushes around the seedling also need light. In order for the tree to get the light it needs and not to be overgrown it has to grow up quickly. To do that fast the tree grows above all at the top.
The stronger the tip grows the more plant hormones it produces which prevent the buds below from growing and sprouting out. The tree does not want to "waste" energy on buds that would get too little light in the grass or under bushes. In order to survive the tree must grow large as quickly as possible.
This ability to produce plant hormones to inhibit the buds below is called apical dominance (apex = tip, dominus (or domina) = decision maker). Absolutely sensible in nature and essential for survival. But this is rather a hindrance for the bonsai stylist.
How can you reduce the apical dominance ?
Quite simply - by removing the top buds (terminal buds). The same every allotment gardener is doing during cutting his hedge. Fewer number of top buds = fewer inhibitory plant hormones. If these plant hormones are missing the buds begin to sprout further down on the tree. And often very numerous. Exactly what the bonsai friend wants.
A lot is written in the internet about the leaf cutting of bonsai trees, about pros and cons. For someone who sometimes defoliate 50 bonsai trees per day in a bonsai nursery the arguments presented are often funny. It's all pretty simple and works very well with most bonsai tree species.
Defoliation of bonsai: What is important ?
- The bonsai species must be suitable. Many deciduous trees (maple bonsai, apple tree bonsai, hornbeam, spindle tree) are suitable for this technique
- The bonsai tree must be healthy and should have enought growth vigor
- The time for leaf cutting must be right: end of june - early july is perfect
- In the case of a total defoliation all tip buds must be removed
- A bonsai defoliation (leaf cut) reduces the size of renewable leaves on the bonsai tree
- Buds inside the crown sprout out. The fine ramnification of the bonsai increases
- Reduction of shock when repotting a bonsai during the growing season by reducing evaporation
- After bonsai leaf cutting in summer, it is easier to wiring a bonsai. The bonsai wire can stay on the tree until next spring
Linden bonsai: Leaf cut + revision
Bonsai defoliation - how is it function ?
- The best period for defoliation is in the middle of the growing season (June - Juli)
- Partial leaf cutting: All leaves and shoot tips on a branch are removed
- Complete leaf cut: All leaves and shoot tips on the tree are removed
- Remove everything at once or first 50% and after 14 days the rest
- Shade the bonsai lightly until the new buds sprout completely
- Do not fertilize until new shoots begins to grow. Without leaves, the tree cannot utilize the fertilizer
- Reduce watering after a leaf cut. Fewer numbers of leaves = less evaporation
- Leaves are not completely removed during defoliation of a branch (or the total tree) -> tree does not sprout again
- Shoot top tips are not completely removed -> tree only sprouts at the tip
- Bonsai leaf cutting on weak trees -> The bonsai may die or more weaken
- Over-watering -> The tree evaporates less water and the roots can rot
- Leaf cutting was performed too late -> no new shoots coming out in the same year
- Leaves will be cut in half but not removed later -> new shoots will likely not appear
Suitable tree species
- Almost all deciduous trees with large leaves (e.g. linden) are suitable
- Healthy and robust plants