I have a black birch tree that is the centrepiece of my back yard. Last year I noticed it did not leaf out near the top and this year it is still only 4/5ths foliage. A few days ago I found a part of the branch that had some buds on it lying on the lawn. Where it was cut from the tree it was almost saw-like straight. The wood was brown and dark at the cut, but green and live further up. I do have a free arborist call-in service that I was going to use, but thought I would also post here, to see if anyone could help with what might be wrong.
Thanks in advance.