Ripen doubles the effects from held Berries when eaten in battle. This affects Berries that restore HP or PP (such as Figy Berry and Leppa Berry), Berries that reduce damage (such as Occa Berry), Berries that raise stats (such as Starf Berry), and Berries that deal damage to Pokémon attacking the holder (such as Rowap Berry). When a Pokémon with Ripen uses Leftovers or Berry Juice, Ripen displays a message but has no other effect.
Outside of battle
It is unknown if Ripen has an effect outside of battle.