I am having a problem with my Japanese maple (Woodbridge – just north of Toronto). 15′ high x 8′ wide. It appears some of the branches are dying and not growing leaves. It was planted about 5 years ago and has been thriving. It is east facing, and gets some morning sun but then is shaded most of the day. It is also shaded by my neighbor’s house. The soil is quite moist here and many of my plants do quite well. Last year I noticed some of the leaves on these branches looked scortched, but this year nothing has grown. I am worried it is phytophthora. Any help is appreciated! Thank you!
Thank you for contacting Toronto Master Gardeners.
Our website has a Japanese Maple Master Gardeners Guide: Japanese Maple
The growing condition you describe are optimum Japanese Maples. Twig die back may be from different causes as per our Gardeners guide:
This is the worst problem of maples. It can be caused by one or more of several organisms, cultural practices, climatic conditions or soil chemistry. The most serious cause of die-back is verticillium wilt. This is a fungus that enters the cambium layer, blocks the flow of nutrients within the tissues, and causes a brown streaking within the layers under the bark. New shoots, twigs, and branches will die quickly. No definitive solutions are available at this time. It is important to sterilize all pruning equipment, keep the tree healthy, and remove infected parts which are then burned. This will limit further spread.
The branches may also have died back from the past winter weather. Constant freezing followed by thawing that happens repeatedly throughout the cold months could also have caused the damage. Pruning out the dead parts is an option, this of course will change the shape of your tree.
This video by Dave Epstein Horticulturist, Japanese Maple Phytophthora and pruning out dead wood.
Pruning Dead Branches of a Japanese Maple
You may wish to reach out to a certified arborist , you can find one here