Thank you for contacting the Toronto Master Gardeners.
Redbud, Cercis,is a beautiful native tree to southern Ontario. Toronto is approaching the northern limit of the range. Trees like your eastern redbud (Cercis canadensis), although really hardy, may be damaged or even destroyed during unusually harsh winters, where temperatures are very cold, drop quickly or fluctuate from warm to very cold. Late spring and early autumn frosts tend to do the most damage to active plant tissues that have not hardened off enough to tolerate the cold. All parts of the plant can be injured, including flower buds, vegetative buds and stems. Damage begins with the softest, actively growing tissues, such as new leaves and tender shoots. Stem damage may not be evident until active spring growth starts.
This year has been extremely difficult on the Redbuds.The warming temperatures in February followed by the freezing rain in April caused severe damage to numerous deciduous trees as well as evergreens. In fact, numerous branches on my Redbud did not leaf out. I also panicked until I checked the branch to make sure if it was still alive. To check if branches are alive carefully scrap off some of the outer bark. If the branch is green underneath then that branch is still alive. These live branches were slow to push out their leaves but with the increase in temperatures they are slowly catching up to the rest of the tree. Make sure to remove any damaged/dead branches.
You mention that you had the fence replaced last year. Another possibility why your Redbud is struggling this year is construction damage to roots from digging machinery. Soil compaction from heavy equipment diminishes soil particle space, therefore limiting oxygen & water retaining qualities and creating a hostile environment for root penetration & growth.
To help your tree recover from it’s trauma and stress I would suggest the following:
Deep thorough watering now and continuing until freeze up.
Remove any competition from around the base of the tree such as grass, other perennials or weeds.
Top dress with well rotted compost.
Add 1-2 inches of mulch around the base of the tree but not right up against the trunk bark. This will provide moisture retention & weed suppression.
You mention that the bark is peeling off of the tree. The bark of a tree is the external vascular system that carries water and nutrients vital to a tree’s survival. Therefore any damage to a tree’s bark can have potentially fatal consequences. What is the extent of the bark damage? If the area of torn bark is more than 25% of the circumference of the branch or trunk, then you may need to consult an arborist. To find a certified arborist, start here:
https://www.isaontario.com/content/find-certified-arborist
Good Luck!