Our ornamental cherry tree has some dead branches in it, which were there last year too. I think the two very cold winters we had might be the cause. I have been water, water, watering and have added fertilizing spikes but I’m wondering if I should lop off the dead branches. Some of the branches look to have life at the bottom but look dead at the top. Thank you for your help.
Thank you for contacting Toronto Master Gardeners.
When trees have dead branches they should be trimmed off back to healthy growth.
Once a woody branch has died it will not start growing again even with watering and nutrients. The area just under the surface of the bark is called cambium. In the cambium are the structures that allows water and nutrients to flow up and down the branch. When the cambium stops working and dies the tree can not replace this structure as there is no flow to the branches.
A quick way to see if the cambium is still alive on a branch is to gently scratch the bark in a small area with your finger nail. If the area is green under the bark, it is still alive; if it is brown the branch has died.
Cherry trees are susceptible to many infections so it is important to remove any dead branches. Trim the dead material back to the main branch where there is living tissue. Dispose of the branches and make sure there is no debris around the tree that could be causing any disease. If you need to do any pruning to restore shape or increase air flow through the canopy, it is best to do the pruning in the winter when the tree is dormant.
Continue monitoring your tree and water if it is dry but make sure you do not over water and have a damp environment which will promote disease.
Fertilizing may or may not be useful depending on the nutrients in your soil. Be sure you do not give too much Nitrogen as that will promote green growth rather than fruit. Do not fertilize late in the summer as promoting new growth late in the season encourages winter damage to the branches as they do not have time to prepare for the winter.
I am including a link with further pruning information for you.
Good luck.
https://homeguides.sfgate.com/prune-flowering-cherry-44171.html