Buy it in Mystifying Forest in the Kecleon Markets for 1000 Poke Dollars
you can't.its impossible.EDIT: Wrong. You can find a leaf stone as a random prize in paradise or in the DLC dungeon "Skill Treasury"
Maybe you get it from a kecleon store not in treasure town but when adventuring
The leaf stone will evolve certain species of pokemon
You get a leaf stone underground.
Pokemon
The only Unova Pokemon that evolves with a Leaf Stone is Pansage.
u go to evolve place and give leaf stone
Pansage will evolve by using a Leaf Stone into Simisage.
Gloom and Weepinbell.I think there are some more Pokemon that evole with a leaf stone but I forgot....
Trade a green shard to the hunter to get a leaf stone.
Well i just restarted my Pokemon Xd and where i found a leaf stone was in the cipher headquarters in the room where you had to fight the peon to save Krane, it was in a chest in the corner of the room i think.
pansage = leaf lampent = dusk