A tree being part Ground-type makes a lot of sense to me, since they are (in the real world) rooted in the ground.
Plus, in Pokémon logic, trees can be Rock-types, so the Grass/Ground-type isn't that strange.
Edit: I know this tree can walk, but it doesn't mean that it can't take root itself in. A lot Ground-type Pokémon don't live underground.
Plus, in Pokémon logic, trees can be Rock-types, so the Grass/Ground-type isn't that strange.
Edit: I know this tree can walk, but it doesn't mean that it can't take root itself in. A lot Ground-type Pokémon don't live underground.