We have a japanese maple that is about 7 years old. It has been very health since we planted it, but this year, for some reason, many of the branches were either leafless or very sparse and is very unhealthy. We had strung christmas lights on them this year and not sure if that is what cause it’s demise. I had them removed and it’s still sick. What can I do. Half the tree is dead. It’s our pride and joy. Please help.
Thank you for contacting Toronto Master Gardeners.
From your picture several possibilities come to mind.
It is difficult to tell but the tree maybe planted too deeply. Trees need to be planted so the spot on the trunk where the roots begin to flair out is flush with the ground. If the trunk is planted deeper the tree will do fine for a few years then start to struggle. The mulch looks like it is right up against the trunk. Pull all the dirt and mulch away from around the trunk and dig down to where the roots begin branching out. Is this below the surface? If so you may want to consider replanting it in the fall so it is at the right height. While you are looking double check you do not see any roots girdling ( growing) around the trunk. This can cause issues after a few years in as well. If you find one you will want to cut the root out so it is no longer pressing on the trunk. When you are done leave the trunk exposed to air so it can dry out. Mulch should be put in a ring around the tree like a donut so there is none touching the trunk.
Another issue this year was the very wet spring then the hot dry summer. Does the area drain well after rain or was the tree sitting in water this spring? during the heat of the summer has the tree been watered? Slow deep watering with a soaker hose over a few hours is more effective than a quick surface watering.
I can not see the leaves in your picture. If your tree has a disease such as wilt you would see discolouring then browning and curling of leaves . What did the leaves on the dead branches look like before they fell off? the following link shows different diseases of Japanese Maples which may help you identify the problem: https://extension.illinois.edu/hortanswers/PlantDetail.cfm?PlantID=342&PlantTypeID=8
No matter what the issue turns out to be you will need to prune back the dead branches. They should be cut back to the first healthy main branch they attach to. If you lightly scratch the bark with your finger nail you can see if it is green underneath, if so the branch is alive.
Another option would be to call an arborist to get their opinion. You can find certified arborists at https://landscapeontario.com/
Good Luck, I hope you can find the problem.