Question
I planted a 16 canadian hemlock 15 years ago in a hedge with 13 other canadian hemlocks.   Since last last fall it has been defoliated from the top down about 65 percent.  It is fairly green with new growth on the bottom.  None of the other trees are having this problem.  I am at a loss but would desperately love to save this tree.  Help!  Than you for your time.

Answer
Dear Charles, This is one of the most frustrating problems in landscaping.  You have this wonderful hedge and one plant has a problem creating a gap in an otherwise perfect row of plants.  The most probable cause for your hemlock's defoliation is either damage or borers, but I think it is probably due to some damage on the trunk of the tree.  The problem is that the top of the tree will not grow new leaves, and you would have to somehow cut off that top of the tree and seal it up with pruning paint just to get rid of the damaged part.  This is always very difficult on evergreens.  The tree might otherwise survive with no further treatment, but it will grow in unevenly, not have a nice top shape to it, and always be out of sync with the other trees in the hedge.  Since it is part of a hedge, I would seriously recommend replacing the tree since leaving it will always leave an uneven area in the hedge.  Plus there is always the possibility that the damage in the tree could cause it to die back further.  You could always dig it up and plant it somewhere else in case it survives.  I wish I had better news, but I hope this information helps.  Please write back if you have further questions.  Good luck, Melissa