Acer palmatum - Japanese maple : how to prune ?

Bonsai pruning

With their very graphic architecture and slow growth, Japanese maples are bushes suitable for bonsai cultivation.

1. Perform a structural pruning in late autumn, as soon as the plant has entered its dormant phase. This is quite a severe pruning, which allows you to give it its general shape. Before acting, take the time to carefully observe the silhouette of the bush and visualise the shape you wish to achieve.
2. During the growing season, carry out maintenance pruning to remove any poorly positioned, damaged, or unsightly shoots. This helps refine the shape of the bonsai. Use scissors to prune mainly the shoots located at the tips, and remove those with very spaced internodes.
3. At the beginning of summer, proceed with defoliation: cut the leaves of your maple to stimulate the appearance of new, smaller, and denser leaves. Be careful: avoid performing this pruning on a subject that is already weakened or sick. You can do this every two years, avoiding the year of repotting, to not further disturb the plant.

When performing significant pruning, you should also cut the roots to the same extent, to balance the root volume and the aerial volume.

We recommend applying mastic to the larger wounds to facilitate healing.

Water your bonsai daily, especially in summer. Provide fertiliser at least once a month. Repot every two years in spring, trimming some of the roots.

Acer palmatum ‘Kiyo-Hime’, pruned as bonsai! (photo Ragesoss)

The training pruning in niwaki

Niwaki pruning, or cloud pruning, is an ancient Japanese pruning technique. It highlights the architecture of the tree and showcases the unique shape of the trunk. It enhances certain characters of the plant, creating the impression of an old tree with a twisted, tortured trunk that has endured the ravages of time… The bush simultaneously takes on a very airy appearance that allows light to pass through. Plants pruned in niwaki style integrate beautifully into zen gardens.

Perform structural pruning between late autumn and early spring, while the tree is dormant. This allows you to give it its overall shape. Form the clouds when the plant is in growth, from spring to autumn.

1. Preferably select a bush with a twisted or leaning trunk. If you have a choice, avoid the straighter specimens.
2. Before intervening, take the time to carefully observe the overall architecture of the plant. Start to visualise the shape you wish to give it.
3. Remove dead or damaged branches, then select the main branches, preferably horizontal branches that are spaced apart. You can also artificially bend them using strings or ropes. Eliminate other small branches and twigs by cutting them back to the base, leaving only clouds of leaves at the tips of the main branches. Distribute these clouds evenly and spaced throughout the tree.

Prune the clouds of leaves at the tips of the main branches. They should form horizontal layers, with enough space between them.

Cares after pruning

Japanese maples do very well without pruning; however, you may choose to intervene to restore a harmonious and balanced shape. Prune in winter, when the tree is dormant, to give it its general form. Remove damaged or malformed branches, as well as those that overlap or cross each other. You can also carry out light pruning during the growing season, from spring to autumn, to identify and remove dead wood, which is much more visible during this period.

The elegant and graphic silhouette of Acer palmatum! Here, at the Botanical Garden of the University of Münster in Germany (photo Rüdiger Wölk, Münster)