you can buy it at the pokeathlon with the points you win.
You have to use a leaf stone on your eevee. Sorry, I don't know where to find a leaf stone though. : ) hope this helped!
evolve pokemon
I'm pretty sure you need to find a Leaf Stone.
at the pokeathlon dome on Thursday
use a leaf stone on your weepingbell.
Oddish-Lvl 21-Gloom-Leaf Stone-Vileplume Exeggcute-Leaf Stone-Exeggutor Bellsprout-Lvl 24-Weepinbell-Leaf Stone-Victreebell Seedot-Lvl 14-Nuzleaf-Leaf Stone-Shiftry
If you're talking about soulsilver then you can get them at the pokeathlon by exchanging your points for it.
you can earn it in the pokeathlon dome on specific days
if you have a leaf stone weepinbell will evolve
gloom
On Monday you can get a leaf stone, Tuesday you can get a fire stone, Wednesday you can get a water stone
In SoulSilver he gives you a Leaf Stone if you show him an Oddish :) Hope that helped-- Taylor