Zemnarihah’s Tree is the tree on which Zemnarihah was hanged. “And their leader, Zemnarihah, was taken and hanged upon a tree, yea, even upon the top thereof until he was dead” (3 Nephi 4:28).
After Zemnarihah was dead, those who had hanged him “did fell the tree to the earth” (3 Nephi 4:28).