i live in toronto with clay soil & use lots of leaves as mulch. my tree is about 5 yrs old. for the past 2 years i’ve had scant leaves & blooms. ive removed all dead wood & cannot find any holes from borers. i haven’t tried fertilizing but it was planted with lots of my compost. it’s looking sick.
The Cornus kousa ‘China Girl’ Tree, or Flowering Chinese Dogwood Tree, is a very beautiful tree. Those of us who have lost trees will share in your sadness and disappointment that your tree is not doing well. My neighbor has one of these magnificent trees and it is in full bloom with rich green leaves. The fact that your tree has had scant leaves and blooms is not a good sign.
As a previous Toronto Master Gardener wrote, there are a few reasons why the tree is not leafing out normally. We had a very cold spring in Toronto this year, and that means that the buds could have been killed in the late frost that occurred in May. The website listed below may help you assess whether the branches are still alive. If they are alive wait a little longer to see if the branches will leaf out. If they are dead, they should be pruned.
https://extension.oregonstate.edu/news/how-examine-deciduous-tree-leaf-out-problems
Another possibility is that the wet spring has caused the soil around the tree to become compacted. This will affect the roots and may lead to branches dying. This is more likely to occur with clay soils. For more information how to address soil compaction, review the following sites:
https://trees-energy-conservation.extension.org/how-to-correct-soil-compaction/
https://worldpermacultureassociation.com/soil-compaction-in-your-garden-fix-it/
However, sadly, from your description, your Cornus kousa may be beyond help. Since it has not leafed out for flowered well for at least two years in a row, this is an indication that it has been under constant stress. The life cycle of deciduous trees depends upon the annual leafing out process to provide the tree with the energy it needs to complete its energy reserves for upcoming winter dormancy and spring leaf-out. Chinese dogwoods do not do well in extremely wet or extremely dry soils. They also prefer an acidic soil pH (5.5 – 6.5). If your garden’s soil pH is higher, this may have contributed to decreased vigour and hence an increased vulnerability to other stress factors. (You can check your soil pH level with kits that are readily available at home and garden centres and nurseries).
Just because it may be the last hope, why don’t you try and transplant it to another spot in your garden, and see if that helps? Find a nice spot that is weed free, add a lot of organic matter, but do not mulch with bark around its trunk, and make sure it is well-watered when you transplant it. Trees do not usually thrive from being transplanted, but maybe it is just a bit unhappy where it is, and a move will do it good. This Master Gardener Guide may be helpful to you: https://www.torontomastergardeners.ca/gardeningguides/planting-a-tree-a-toronto-master-gardeners-guide/