Turtwig evolves into Grotle once it reaches level 18. Grotle evolves into Torterra at level 32. Also known as the Tiny Leaf Pokémon, Turtwig is one of the first Pokémon a player encounters in Generation 4 games.
To reach level 18, Turtwig needs to gain experience points in the game. Experience points can be gained by battling other Pokémon in the game. Turtwig evolves immediately once it reaches level 18 unless the player presses the B button to stop the process. Because Turtwig is one of the starter Pokémon in the game, the player should be able to level it quickly.