Why does one of my maple trees not have top leaves and turns fall colors early?

There are several reasons this could happen. Certified Arborist Wes Hopper lists the likely causes of the problem including girdling roots, squirrel damage, or verticillium wilt. He says more investigation may be necessary to determine the actual cause.
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Related Videos:
How do I keep the squirrels from stripping the bark off my maple tree?
Removing Suckers from a Maple Tree Trunk

​Related Resources:
Tree Wounds
Verticillium Wilt - A Serious Disease of Trees and Shrubs