Pruning Japanese Maples

A major sin in landscaping and gardening is the constant neglect of pruning and shaping our plants. So many enthusiasts get busy and let their plants, such as rhododendrons, get too high or too floppy. This is true of flowering shrubs, dwarf conifers, and even perennials in most gardens. In far to many cases we let a fine plant go unchecked for a few years and then suddenly realize that it just can’t be that big anymore and still live in its allotted space. So we have to either tear it out or prune it back drastically and start over again. The latter leads to several years of unsightliness or even worse the tree might not recover from such treatment. Thoughtful pruning and shaping should be done each year. Better still limited but constant pruning to shape a plant every season of the year is desirable. Hence, shaping should start once the young plant is established, about two to three years after planting. These detailed remarks are given to emphasize the need for pruning all Japanese maples.

Major pruning should be done during the dormant season after the leave have fallen, from late November to early January, well before the sap starts rising prior to leaf production in the spring. Corrective pruning and training can be done at any time of the year, however, except when the sap is rising and all the plant’s energy is devoted to the emergence and development of the young leaves. Cuts should be made just beyond a pair of buds on the twig. Usually, this will then produce two side shoots. When removing a larger limb, like any other pruning, the cut should be made just above the branch collar- the ridge or line where the branch joins an older branch or stem. Never cut below this natural barrier against the ingress of disease from a pruning wound. Cutting beyond this point not only gets behind the plant’s last line of defense, it also creates an even bigger wound surface for disease to attach. At the same time, an unnecessarily long “stub” should not be left, as it provides a greater food source for any disease to build up its strength before penetrating the tree’s natural defense system.

The need for SHARP pruning tools cannot be overemphasized. A clean pruning wound heals much more quickly than jagged, torn wound created by blunt tools, and the wound calluses over more effectively. To prevent spreading disease from tree to tree, it is good practice to clean and sterilize pruning tools regularly. The use of tree-wound paint on the cut surfaces is not recommended. Studies and trials in the 1980’s and 1990’s showed clearly that allowing the wound to dry out discourages the germination of disease spores which are inevitably already on the wood surface, can live like lords, well protected from the elements and with ample moisture and food to thrive.

The fine twiggy growth in some larger maples must be removed, especially from cultivars in the Dissectum Group of ACER PALMATUM. A tree that is too bushy inside invites insect and disease problems. But, perhaps more important, is proper display of the plant’s structure. The cascading, undulating, and twisting, branches in this group can be as beautiful and interesting as the foliage. Part of the beauty of these maples is the trunk and limb structure and texture. Periodically removing the inside growth of these trees enhances the display of the graceful trunk and branch structure during the winter months when the foliage is absent. In the case of “Sango kaku” (coral-red shoots) and “Aoyagi( bright green shoots), the bark and shoot color is the outstanding feature and should be exposed.

Additional resources: Deciduous Tree Pruning Calendar

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