In Pokemon diamond how do you change shaymin from sky form to leaf form?

To change Shaymin from Sky Form to Land Forme in Pokémon Diamond, you must use the Gracidea flower.

1. Go to the Flower Paradise.

2. In the center of the clearing, use the Gracidea flower on Shaymin.

3. Shaymin will transform from Sky Forme to Land Forme.