Half-dead Maple

Question:

My maple tree is ten feet from the west side of our white garage, which is attached to a two story white home. Half of the tree has many dead branches, the other side is in full leaf. What causes this?

Minnesota Master Gardeners say:

 If 1/2 of the tree has dead branches, I'd presume that the roots that feed that part of the tree were damaged somehow. Was any construction done in that area? The roots spread far and wide in maples, so any damage to them will affect part of the tree. Another possibility could be from winter injury that caused sunscald or bark crack on a large branch or the trunk of the tree. Check this site for more information:

http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/P466winterinjury.html

Cankers on maple can cause a section of the tree to die too. Check the limbs that lead to the injured part of the tree for a lesion. Check this site for more information on cankers on maple:

http://www.extension.umn.edu/distribution/horticulture/DG6659.html#maple

Since part of the tree is dead, that section can be removed, but it would be important to determine if the tree is stable. If it is a hazardous tree that could fall on the garage or house, it should be taken down. If this is a large tree, I would have a certified arborist examine the tree to see if it can be saved.

You might also read this on shade tree decline:

http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h412shadetreedecline.html

and this on verticillium wilt:
http://www.extension.umn.edu/distribution/horticulture/DG1164.html