Hello – We’d very much appreciate your opinion on our Japanese Maple. We want to prune it into a vase shape so it can stop hitting visitors and let us see other plantings. It’s about 20 years old. The trunk is made up of two 13″ diam trunks. (Together they’re 17″ diam.) The three branches we want to prune off are 4″ diam each. Can we prune them all off now or should we space out the work to avoid stressing the tree? We’d ideally like to prune them all off in July so the tree doesn’t look lopsided. Thank you.
Thank you for contacting the Toronto Master Gardeners.
Any kind of severe pruning will always stress a tree. When and how you prune can reduce this stress. You mentioned that you wanted to complete the pruning in July. This could be an issue if the weather becomes more summer like soon. You should never prune a Japanese Maple if the temperature is above 26 degrees celsius. Have a look at your tree to determine whether the removal of your three branches will expose leaves that are currently being shaded. This could result in scalding of these protected leaves.
Thank you for sending a photo of the trunk from where the three branches are growing. Please make sure you do not cut the branch flush with the collar on the tree. One half inch away from he collar is ideal. The collar has a self healing mechanism so you do not need to add any kind of commercial healing compound. As well, since your branches are quite thick, it will require three steps o remove the branch. The first cut is made on the underside of the branch, the second on top of the branch and the third cut one half inch from the collar. This way you avoid breaking the branch accidentally. The following web site may be helpful in this endeavour.