Before I get started let me caution that defoliation is not for beginners in bonsai. I am very commonly asked about defoliation of immature and or sick trees that are desperately clinging to life and holding on to a few large and weak leaves. Defoliation is a very valuable and powerful technique but not to be used by new bonsai growers or those with trees that are not devastatingly healthy and growing. I would suggest that if you have not grown bonsai for at least 1-2 years and have trouble with plants staying alive and healthy under your care do not practice defoliation techniques. Defoliation is the deliberate complete or partial removal of the leaves of a bonsai tree. The technique is used to reduce the leaf size thus making the new, replacement leaves smaller and in better scale to the tree's size. Defoliation is often done prior to exhibiting or photographing the tree. Another benefit of defoliation is the increase in branch ramification that occurs with defoliation. This to me is THE main reason to defoliate. |
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HOW TO DEFOLIATE The process of defoliation is simple; using a sharp scissors cut off each leaf leaving the petiole or stem. This may take a few seconds on a very small tree or many hours on a large tree. On some species of tree it may be possible to pull the leaves off by hand and save the time of cutting each leaf off individually. Often the tips of the branches will pull off along with the leaves. If this occurs leaf removal with scissors is the way to go.
The residual leaf stem/petiole will fall off in several days. In two to four weeks the tree will begin putting out new leaves. Many of these new leaves will be in areas of the tree that never had any foliage.
This process is called creating back-breaks. If done properly each twig may develop anywhere from none to three or more new branchlets on each branch.
Back-breaks are a really nice help to creating more twig density on the tree and advancing the look of maturity. Most of the new leaves will simply replace the old ones, but the new leaves will be much smaller, cleaner and undamaged making the bonsai look very refreshed. After the first new leaf emerges and enlarges a second and third leaf will shortly emerge. As each successive leaf emerges and hardens off it will be larger than its predecessor. Usually by the 4-6th new leaf the plant's normal leaf size is reached. All growth after that point will be of the normally sized leaf. If you wish to keep the newly growing leaves small you must stop the growth after the second or third new leaf by pinching all the tips back. This will hold the plant another two weeks until growth starts again. Unfortunately this second growth will usually be with normally large leaves.
HOW OFTEN TO DEFOLIATE
Under typical indoor cultivation I would not recommend defoliation be used except every one to two years. In tropical areas with trees growing outdoors the fig may be leaf pruned or defoliated two, three or more times per year.
But these trees are under ideal growing conditions and are much stronger and able to tolerate the stress of defoliation. If you are experienced and are growing your trees under strong artificial illumination then defoliation can be done two or even three times each year.
Outdoor tropical growers are lucky and with healthy trees can defoliate even more frequently. Defoliation is a useful technique but the goal is not to see how many defoliations you can accomplish each year but to move your tree along to a more mature design.
BEFORE DEFOLIATION
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| DEFOLIATION IS STRESSFUL TO TREES
Any partial or complete defoliation is a stress to the tree. All green plants with leaves need the leaves to photosynthesize. Photosynthesis is the only source of energy for green plants to grow and survive. When leaves are removed photosynthesis is greatly reduced until new leaves equal to the ones removed are replaced on the tree. The tree must use its stored energy reserves in the branches, trunks, and roots to survive and eventually to replace all the removed leaves. Until this happens the tree is in deficit mode. The stores are depleted and can only be restored after the new leaves come out and begin photosynthesizing for several months. Should the tree be further stressed by chilling, over watering, insects etc. the whole tree or parts of it may die.
CARE AFTER DEFOLIATION
After defoliating the tree must be kept in its normal light position. If the tree is moved to less light the new leaves may actually grow out larger than the original leaves. Watering is reduced since the tree without leaves will not require a normal amount of water. Keeping the tree wet may result in root rot and damage to the tree. No fertilization of the tree is required until the tree puts out at least two new leaves on each of its growth points. Do not repot the tree after defoliation; if a change of pot is needed this should be done two months or more before or after defoliation. The double stress of simultaneous repotting and defoliation is not advised. Wiring after defoliation is a very useful tool. Post defoliation the tree’s structure can be studied and appropriate measures taken to improve the shape of the tree. This is an additional stress to the tree and should only be done by experienced growers. Wiring at this time is also much easier as leaves are not in the way and small buds hidden by the leaves can be avoided.
WHEN TO DEFOLIATE
Defoliate when the tree is actively growing. That means when the tree has put out and matured at least three new leaves at each growth point. A resting or dormant tree can be defoliated but I do not advise this for indoor fig growers. If the tree is under stress such as disease, insects, change of location, large changes in temperature then do not defoliate. Defoliate three weeks before you wish the tree to be at its peak beauty. This may be prior to photographing or displaying the tree in a show.
PARTIAL DEFOLIATION
Defoliation of only some of the tree is used in specific circumstances. Sometimes one branch of a tree is thinner or weaker than it should be. Defoliate the whole tree but leave the weak branch alone. This will allows the weak branch to grow more vigorously and catch up with the defoliated portions of the tree. The non-defoliated branch will continue to grow while the defoliated branches are busy putting out new leaves and not thickening quite as much. Done repetitively over a few years a thin branch can catch up to its neighbors. Theoretically a branch that is too heavy can be defoliated while leaving the rest of the tree with full foliage. This slows down the growth of the too heavy branch and the process repeated over some years will allow the defoliated branch to come back into scale with the rest of the tree. I do not recommend this as these discouraged branches can die back or die completely.
When a tree needs some leaf reduction but the tree is not splendidly healthy it may be possible to remove the largest leaves. This weakens the tree slightly and the replacement leaves may be smaller. Also some trees will have an assortment of leaf sizes present. By removing only the large leaves the whole tree is brought into more harmony. Another option is to cut all the leaves on the tree in half. Most figs will respond by sending out new leaves that are smaller but not as small as with total defoliation. It's a less stressful means to reduce the leaf size but probably the leaf size reduction is less than maximum. During this time the tree also looks quite scruffy since it has rather funny cut leaves. These cut leaves are removed after the new leaves are hardened off.
SIGNS OF PROBLEMS
All these indicate that you goofed. Likely the tree was not as healthy as it should have been. Do not do anything more to stress the tree and allow it grow for one year without interference, and keep your fingers crossed.
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 Ficus in 1992 with large leaves and coarse branching
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The same ficus in 2002 showing dense branching, defoliated, wire
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TREES TO DEFOLIATE
Trees that I find particularly suitable for defoliation are most species of figs and Schefflera and Brassaia.
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TREES NOT TO DEFOLIATE
Dwarf/Miniature tree forms Shohin bonsai Trees that need repotting Needled/coniferous trees
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 Same tree after defoliation, tight canopy and smaller leaves |
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CONCLUSION
Defoliation is a fabulous tool when used properly. Defoliation is not for all trees and should not be done by beginners until they are confident in their horticultural skills and familiar with the species of tree. Properly done defoliation can speed up the process of advancing your tree to a higher level. Done improperly and the tree may be dead or ruined. - - - Jerry "Bonsaihunk" (www.bonsaihunk.us )
NOTE BY DAVID: Defoliation is a great technique provided your trees are growing vigorously. Our True Indoor Bonsai are the easiest and most successful but to improve and train them, they must be healthy and growing well. Give it good light on a window sill and contact Jerry or I if you have questions or if we can be of assistance. ~~~David (david.f@fukubonsai.com)
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