Selective Pruning on Japanese Maples
Proper pruning of a Japanese maple is important to maintain the structure and over-all health of the tree. Several tasks should be performed routinely to ensure proper development of the tree. The best time to prune, however, is in late fall to mid-winter when the trees are dormant. Having a sterile pair of hand pruners is very important. If the same pruners are used to cut out diseased branches and live branches, the disease could spread. This can be easily prevented by sterilizing them with a bleach or alcohol solution.
One must remove the dead wood to prevent the diseased branch from affecting the health of the rest of the tree. It is best to cut the diseased branch all the way back to the healthy wood to ensure its entire removal. General structural pruning is necessary to encourage proper branching structure, as well. For instance, it is necessary to remove a branch if it is resting on or overlapping with another. Select the branch that is heading in the most desirable direction before deciding which one to remove.
Pruning smaller branches to maintain a rounded, neater shape to your tree is another essential step in caring for maples. However, this type of pruning requires more time and patience. Maples have branches with opposite buds at each leaf node. It is best to trim down to just above these buds, such that they are at the tip of the branch. If some of the stem is left above these buds, the branch will have a dead tip with no new growing points that could allow disease to develop.
Some variegated and dwarf cultivars can develop faster-growing branches with green leaves, called reversions. Because these mutations no longer possess the characteristics of the original plant, they too need to be trimmed out to maintain the colorful, variegated leaves.
A similar type of pruning should take place on newly-grafted maples and conifers. The selected variety is grafted onto an average Japanese maple with green leaves. Especially when the plant is young, this "rootstock" as it is commonly called, can regenerate vigorous foliage of a typical green color from the plant's base. If these are not hastily removed, the young graft can quickly become overtaken by the foliage of the rootstock.