Question
When is the best time to trim a Japaneese Maple and how far back can you trim it?

Answer
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抯 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抯 last line of defense, it also creates an even bigger wound surface for disease to attach. At the same time, an unnecessarily long 搒tub?should not be left, as it provides a greater food source for any disease to build up its strength before penetrating the tree抯 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抯 and 1990抯 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.