We live in the city of Toronto. We have a tulip tree in our back yard. It is planted in partial sun. Every year, the leaves turn yellow with dark brown spots and end up falling off the tree. I attach a picture. What could be the issue? Thank you
There are a couple of possible issues that might be affecting your tree. Liriodendron tulipifera are known to be highly drought sensitive, and they require regular summer irrigation to prevent yellowing and leaf spotting, which is followed by early leaf drop. We have seen the stress caused to trees and other plants by the recent summer weather patterns in Toronto which feature very heavy rains followed by drought. A regular deep watering program can be helpful here.
Tulip trees are also susceptible to fungal leaf spot which causes the symptoms your tree is experiencing: brown spotting, then yellowing and early leaf drop. This is typically not a serious issue but it is important to practice good maintenance around the tree to prevent re-infection: rake up all of the affected leaves and dispose of them in the garbage rather than composting them.