Why are some limbs of my Japanese maple not leafing out?

Likely this is the result of some sort of mechanical damage. Certified Arborist Wes Hopper says the tree likely has girdling roots or weed eater damage. He also lists some other possible causes. He does not suggest replanting another Japanese maple in the same location.
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Related Videos:
Japanese Maple Basics
When should Japanese maples start leafing out?

​Related Resources:
Tree Wounds
Japanese Maples