My son in Whitby has a hydrangea tree that appears to have died.
How can you tell for sure and what causes it?
Thank you for contacting Toronto Master Gardeners.
It is still very early to be determining if a Hydrangea has made it through the winter. There are many types of hydrangeas so I am not sure which variety you have or whether it is one that flowers from new wood or on last years branches or which zone it prefers.
With many shrubs and trees if you gently scrap a small spot on the tree with a finger nail you can see if there is any living wood underneath. A healthy plant will have green hue to it. That being said if a branch appears dead the plant may sprout new branches from dormant buds.
You do not mention if the plant was healthy last year or if it showed any signs of stress or disease. Is the plant in a sheltered area or was it exposed to heavy winds, snow plows, road salt or any other environmental damage? What are the symptoms that make you suspect the plant is dead? Without knowing the type of Hydrangea and what zone it is suited for as well as the previous health of the plant and its current location it is very difficult to make any predictions on what may be causing the problem.
That all being said it is very early in the spring to be giving up on the plant. I would wait more time to see if any signs of life show over the next month.
I have included some articles on Hydrangea Trees for reference.