Although defoliation is “generally” recommended as a bonsai training technique it actually requires considerable thought and it’s necessary to contemplate each specific tree and the purpose of removing foliage. Today I’ve been told that Ryan Neil and others do not recommend total defoliation of healthy maples. Unfortunately, I did not study with Ryan, whom I respect, and others. I must have skipped the defoliation chapters in the books studied. I’ve learned through intense study (both in the US and Japan) and actual practice for well over 50 years that plants, especially Japanese maple cultivars have diverse growth habits and respond differently to bonsai training techniques.
There are numerous reasons for defoliating deciduous, and even broadleaf evergreens, such as for increasing the number of twig ramification, reducing leaf size, transplanting out of season, reducing vigor on developed trees, energy balance, preparing trees for exhibits, improving air circulation and sun, improve autumn coloring, enjoying colorful spring shoots again, facilitating easier wiring, reviving dehydrated trees, eliminating pests and disease and more. The health, age, size, stage of development, climate and reason for defoliating a tree must be carefully considered, especially with established developed specimens. Undeveloped trees can generally withstand more stress than more developed trees.
June 2020 Katsura Japanese Maple Defoliated Bonsai And Garden Tree. Both Are The Same Age, My 40 Year Cuttings.
I recommend that the foliage matures and trees are fertilized before defoliating in late-spring and summer for maximum results in developing a new flush of growth for training or display. Timing is important to allow the new growth to mature before cold weather arrives. I’ve actually defoliated maples in August with good results, but do not recommend that late a date. Aftercare is important considering sun exposure, watering and fertilizer applications. The subsequent new growth can be trained for different purposes. Sometimes the fine delicate twigs are not as winter hardy as thicker branches.
Katsura Japanese Maple 2010 after growing in the garden for a few years. Before pruning.
2010 After Pruning.
I shared a few photos of my Katsura Japanese maple, Acer palmatum ‘Katsura’ in my original posts in Facebook and the Bonsai Nut Forum. The complete history of this bonsai is attached here. Both the bonsai and the garden tree are the same age, my cuttings about 40 years old and were planted in my garden in 1988. About ten to fifteen years later one of the maples had an interesting shape and it was lifted and trained for bonsai. Katsura Japanese maple is a vigorous grower and this specimen has only been in training for about 15 years after lifting from my garden. It’s a relatively large size and heavy bonsai. Since The outer canopy silhouette was the main reason for total defoliation. After removing all the leaves thick heavy branches were visible and will be corrected in the future.
May 2014, Excellent Spring Coloring.
May 2020, Spring Coloring.
June 2020 Before Defoliation.
June 2020 After Defoliation.
June 2020 After trimming, but before eliminating thick branching.
At the same time as totally defoliating the Katsura Japanese maple posted, I partially defoliated another Japanese maple, Acer palmatum, which was not posted. This special and unique tree is one of the original shohin bonsai from the Matsudaira Collection. Now over 120 years old this bonsai has an interesting history. Count Yorinaga Matsudaira and his wife created the largest shohin bonsai collection in Japan in the 1930s. He was infatuated in bonsai and wanted to see how small a bonsai could be created and maintained. Count Matsudaira, along with Norio Kobayashi established the Kokufu Bonsai Exhibition in 1934. This Japanese maple bonsai is from the Matsudaira Collection and was displayed in at least two Kokufu Bonsai Exhibitions in 1957 and 1974.
1958 Kokufu Bonsai Exhibition
1974 Kokufu Bonsai Exhibition
June 2020 After Partial Defoliation
So, this is an old bonsai and not as vigorous as younger trees so it should not be completely defoliated to maintain health. However, I have a few times totally defoliated the bonsai during the past 36 years I’ve been caring for it. It’s been fun and a privilege to be able to care and continue the training of this distinctive and historical bonsai.