And on every continent, there was always a species of demon Treant that existed there.
Whether in the forest, or on the plains, it appeared frequently.
While Treant is a monster of the tree, its outward appearance is not fixed.
Stone Treant looks more like a potato.
Cactus Treant looks like a cactus.
They each had various appearances.
According to a story that I heard, there is even a type called Elder Treant that is able to manipulate water.