You have to level Shroomish to level 45 (Gen V) to learn it then you can evolve, after evolution there is no way for it to learn it.
Chat with our AI personalities
Shroomish and Breloom.
I had a Shroomish once...too many powder attacks for my liking...good for catching Pokemon however. Level 23 it evolves at, into Breloom.Shroomish evolves into a breloom at level 23. There are no special conditions that need to be met for it to evolve. I recommend not evolving it until level 54 because it learns spore which breloom cannot learn.
Go for breloom since he has poison heal witch is useful with the toxic orb. Beloom also has the move spore witch is great with focus punch.
It can learn Mach Punch, but it should be able to learn upon evolution. Breloom is able to learn Mach Punch at level 23. If you think it was forgotten, it can be relearned by the Move Reminder in Fallarbor Town. If you are playing Pokemon FireRed or LeafGreen, the Move Reminder can be found in Two Island in the house next to the Game Corner.
Shroomish learns the following moves before he evolves to Breloom: Absorb (Start) Tackle (lvl 4) Stun Spore (lvl7) Leech Seed (lvl 10) Mega Drain (lvl 16) Headbutt (lvl 22) But, if you stop its evolution which starts at level 23, he can also learn these moves: Poison Powder (lvl 28) Growth (lvl 36) Giga Drain (lvl 45) Spore (lvl 54) If you want a specialized GRASS Pokemon I would keep it a Shroomish for a while, but then you'll miss out on the FIGHTING type attacks that Breloom learns like Mach Punch and Sky Uppercut