Maybe I should have trimmed some more vines before backing in there.
I had sawed off that privet. It was supposed to push to the side when I backed the tractor with mower in.
Instead, the grapevines and Smilax decided that invasive exotic Chinese privet would go up on top of the tractor canopy.
Probably I would have noticed earlier, but I was concentrating on not backing into a tree and not getting caught around the throat by catbriars. You know those Smilax with the stout sharp thorns and thick stems: Smilax bona-nox.
Note to self: next time take a machete. Cutting each vine with clippers took a while.