I planted a japanese maple 3 years ago and it has done well in my garden here in the Niagara Falls, ON area
This spring we had a very hard late frost and most of the upper branches have not recovered. We do have some leaves on a few select branches and we are seeing some slight growth of new leaves from the living stems and branch but it it largely empty. I wanted to replace it but the emergence of new growth show its trying and i will keep it for another year anyway to see if it bounces back next spring. Should I fertilize it this year and what product is best to stimulate the new growth and strengthen the tree
Thank you for contacting Toronto Master Gardeners with your question.
We have recently received several questions concerning weather-related damage to Japanese Maples.
To care for your tree now, the best approach is to prune back the dead branches. To check if you have pruned enough, use your fingernail to gently scrape the bark on the branches and trunk, starting at the tips and working back toward the base of the tree, until you see green, healthy wood below the bark. If you do find healthy green wood, prune the tree back to that point. Apply mulch in a ring around the trunk and water the tree regularly and deeply when soil is dry.
Your tree may revive and send out new leaves, but this is not certain. Note that a stressed tree may be a target for disease and insect damage before it is able to fully recover, so watch over it carefully and promptly address any problems that arise.
The new growth may be weak and spindly, requiring careful pruning over the next few years. Here is an excellent article on pruning, reviving and fertilizing seriously damaged Japanese Maples, published by the University of Missouri, https://ipm.missouri.edu/meg/2008/3/Caring-for-Freeze-Damaged-Japanese-Maples/
The following links offer some very helpful information on fertilizing your tree. It is recommended to feed Japanese Maples in late winter while the ground is still frozen or after the last freeze in spring. Do not apply high levels of nitrogen to the soil around your tree as this may result in excessive shoot growth which can weaken it. Try a controlled slow-release type fertilizer instead. Mulching and careful irrigation over the next few years may also help your tree to survive.
If you need to replace your tree please take a look at our tree planting guide for maximal success. https://www.torontomastergardeners.ca/gardeningguides/planting-a-tree-a-toronto-master-gardeners-guide/
Good luck reviving your Japanese Maple.