Our huge, beautiful tree in our backyard in West Toronto by the lakeshore, developed buds in late April, but dropped most of them in early May after some serious cold in the spring. Since then we are both leafless and flowerless - now mid June. I noticed another of the same tree in the neighbourhood is in the same situation, though it's about 1/5th the size. The tree is about 25' high and I'd guess to be between 40-50 years old. Can they die suddenly like this, or is this more likely some kind of dormancy? Any suggestions greatly appreciated.