As part of its ongoing efforts to promote every single Pokémon out there, The Pokémon Company has shared a special post dedicated to Turtwig:
Did you know? Photosynthesis occurs across its body under the sun. The shell on its back is actually hardened soil. It undertakes photosynthesis with its body, making oxygen. The leaf on its head wilts if it is thirsty.
Source: @Pokemon
Source: Pokemon
