Bellosem(i spelled it wrong i know)or you can use a leaf stone to evolve it into to veleplume
Use a leaf stone on your Gloom. Ta-da! You now have Vileplume!OR use a Sun-Stone on it. Ta-da! BELLOSSOM!!!!
Just give a leaf stone to it tomake it evolve into vileplume and a sun stone into bellossom
Gloom evolves into vileplume by leveling up or leaf stone. It also evolves into bellossom by a sun stone
Use a leaf stone on a Gloom if you want a Vileplume, but if you want a Bellosem use a Sun stone on a Gloom. Oddish evolves into Gloom at lvl21
Gloom evolves into 2 different pokemon. If you use a leaf stone, it will become Vileplume. If you use a sun stone, it will become Bellossom. Also, level it up after you give it the stone.