The leaf stone is what you use. You can get one in Castelia city.
To evolve Pansage/Panpour/Pansear you have to use a leaf stone on Pansage, a water stone on Panpour, and a fire stone on Pansear.
Pansage does not evolve by leveling up, it evolves if you use a leaf stone on it.
Pansage
It won't evolve until you've used a Leaf Stone on it.
You have to use it on him you aren't supposed to give it to him
Pansage is capable of evolving at any level because it evolves by using a Leaf Stone on it.
Pansage is capable of evolving at any level because it evolves by using a Leaf Stone on it.
Pansage evolves into Simisage when you get the leaf stone from Castellia city from a guy at the docks.
pansage
You can catch Pansage in the Lostlorn and Pinwheel Forests. You can also get it as a gift in the Dreamyard (in the top right corner of Striaton City) if you chose Tepig. This is not needed, but: Pansage evolves, using a Leaf Stone, into Simisage. You can get the Leaf Stone in Castelia City.
Pansage evolves with a Leaf Stone.
give it a leaf stone