Good sleuthing over the weekend! As John, Karen, Jimbo and Al suggested, there is something stuck on the side of this Norway maple (Acer platanoides, which is Latin for “maple that takes over the planet”). In fact, the reason that I, with my pathetic ID skills, know that it’s a Norway maple is because it’s a nursery tag stuck in the tree:
This type of injury really bugs me, because it’s entirely preventable. One of the cardinal rules of transplanting trees and shrubs is to remove all foreign material. And this is a perfect example of why. I don’t know the history of this tree, but this is was I think happened.
The tag was on a branch of the young tree; as the branch increased in girth, it became girdled by the plastic and died back. At the same time, the girth of the tree increased to encompass the base of the branch and the tag. The dying branch was either torn from or broke off the trunk, creating a tear in the bark and creating the horizontal scarring at the base of the wound.
If you’re hopeless with plant names (like I am), keep an electronic database of all the plants you’ve installed in your landscape, including the name, the date installed, and any notes, especially for failures (e.g. not cold hardy enough, invasive, too large, slug snack, etc.).