I'm writing from Vancouver Canada. In the courtyard of the housing co-op
we have a magnolia that's been growing there for years. In the last
month or so I've noticed that the leaves of the tree are yellowing and
dropping off. They are everywhere.

I know nothing about the maintainance of magnolias but the full-scale
shedding of leaves, at the beginning of summer can't be normal. What is
wrong with the tree and what can we do about? Any advice would be
appreciated.