While battling Paul's Honchkrow in Aiding the Enemy!, Turtwig evolved into Grotle, but lost due to its lowered Speed. But after learning how to cope with its defense from Paul's Torterra when it fought Gliscor, Ash managed to make Grotle stronger and Grotle learned Rock Climb. Since evolution, Grotle managed to defeat foes like Candice's Sneasel.
After being used in a Gym Battle against Volkner, which got postponed, Grotle evolved into Torterra during a battle with Team Rocket.
With its new size and strengths, Torterra now knows more powerful moves such as Leaf Storm in addition to the moves Energy Ball, Rock Climb and Synthesis. Despite its size and power, it has been defeated in several battles against Pokémon it should have an advantage over: Volkner's Electivire, Bertha's Hippowdon and Paul's Drapion, though mostly because not only did they have moves that Toterra was vulnerable against, but they also had better maneuverability over it and it's massive size made it an easy target. Also even when it lost, it managed to at least put up a close fight.
Ash decided to leave Torterra at Professor Oak's Lab when he made a fresh start for Unova. It currently resides at Professor Oak's Lab.