you need to train them in many grassy areas. try looking for Pokemon that match there level and are hard to compete with.
It will evolve when it learns Double Hit, which the Pokemon will learn at level 32. So, level it up to level 32.
level it up to level 32 i think and have it learn ancient power
To evolve your grotle into torterra, just level it up to Lv. 32. Get that?
When Aipon level up it learns "Double Hit" at level 32. Then he Evolves
level 32
level 32
level 32
level 32
Level 32.
Level 32.
32
level 32