Train it to level 40.
Ferroseed evolves into Ferrothorn at Lv. 40.
Ferrothorn
Krokorok evolves into Krookodile at level 40. Frillish evolves into Jellicent at level 40. Ferroseed evolves into Ferrothorn at level 40. Those are the only pokemon in Unova that evolve at level 40.
Ferroseed evolves at level 40
Ferroseed evolves into Ferrothorn at Level 40 Ferrothorn
Ferroseed does evolve in Ferrothorn at level 40.
Ferroseed evolves at level 45
It evolves by leveling up. Ferroseed evolves into Ferrothorn at level 40.
Lv 45
Ferroseed evolves into Ferrothorn at Lv. 40.
Ferroseed will evolve into Ferrothorn.
Level 40 ;-)
You train it to level 40
Ferroseed evolves into Ferrothorn at level 40.
Ferrothorn
Through leveling up; Ferroseed will evolve into Ferrothorn at level 40.
Krokorok evolves into Krookodile at level 40. Frillish evolves into Jellicent at level 40. Ferroseed evolves into Ferrothorn at level 40. Those are the only pokemon in Unova that evolve at level 40.