After being used in a gym battle against Volkner, which got postponed, Ash's Grotle evolved during a battle with Team Rocket. With its new size and strengths, it 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 (however although Torterra was part Ground type he did not know any Ground type moves and his Grass type charactiristics made him more vulnerable to Drapion than most Ground types). 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.
It will reappear along with all of Ash's Pokemon in an upcoming episode of Best Wishes Season 2.
When it was a Turtwig, it had it's own way of showing affection by biting on someone's head.
Torterra is the only Pokémon in Ash's Sinnoh team that has never defeated any of Paul's Pokémon.
As a Turtwig, it was more active and very quick, but when it evolved into a Grotle it lost it's speed and became less active.
Throughout it's evolution, Torterra has relied on specific stats to battle. As a Turtwig it relied on speed, accuracy and evasiveness, as a Grotle it relied on defense, patience and precise attacks, and as a Torterra it relied on attack power, strength and healing.
After evolving from Grotle to Torterra, its was the first time Ash had 2 fully-evolved starter Pokemon from the same region.