My Japanese maple is about 16 ft. high and spreads about 12ft. wide. It gets morning and late afternoon sun. I have never had the soil tested, but I believe it’s clay-based. The tree has grown so beautifully up until the last few years.
There are 3 parent stems, 2 of which are a little larger than the third. Over the past few years, the bark of the 2 larger stems showed damage closer to the ground. Since that time, leaves on the lateral branches from these 2 stems have slowly stopped growing. Last summer, some leaves appeared, but this year, nothing so I’m assuming these have died.
The third, smaller plant stem seems to be fine. The leaves have grown as they normally would. I have started trimming the top branches slowly. I’d like to eventually cut the 2 damaged parent stems down to the ground. Do you think this will cause the third stem to eventually die? I’m hoping that by cutting down the other 2 stems, more energy will be transferred to the smaller, living stem and keep it going. What are your thoughts on this? Is there a way to trim the branches so as not to cause any shock to the third living stem? Also, can you recommend a good fertilizer? Any help you can offer will be much appreciated!
Thank you for contacting Toronto Master Gardeners. We receive many questions on Japanese Maples,
Our website has a Japanese Maple Master Gardeners Guide: Japanese Maple
Reasons for Japanese Maple die Back: Japanese Maple Questions Toronto Master Gardener Website
Twig die back may be from different causes as per our Gardeners guide:
Twig die-back
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 want to improve your soil for long term benefits The city of Toronto website provides information “IMPROVING YOUR SOIL ORGANICALLY FOR
SUCCESSFUL GARDENING, Successful organic gardening begins with the soil – it is the engine of the garden. Improving your Soil
If you want a quick remedy, purchase the fertilizer: make sure you follow the directions on the package and ask for assistance at the garden centre if you have questions on how to apply the fertilizer. The best time to fertilize a Japanese Maple is in the spring or this time of the year. The slow-release granular fertilizer or spikes with a nitrogen content of 10 to 15 is a good choice. It would be best if you did not leave the slow release above ground, dig holes 1.5 five times from the longest branch, all around the tree and place it in the hole. This Wikehow website provides details on how to fertilize a tree. How to Fertilize a Tree
You may wish to reach out to a certified arborist , you can find one here