How do you get breloom in Pokemon ruby?

You want a Breloom hunh? Well, catch a Shroomishin Petalburg Woods or anywhere else and train it until it evolves. If I can remember correctly, it should evolve anytime before it hits Level 40, so if possible, give your Shroomish the EXP share and take your bestPokemon to the Elite Four and fight them over and over until he levels - If you can't do the Elite Four then just find trainers, and the best trainers for training are Breeders, but any will do. - Breloom is a very useful Pokemon as it has control over considerably powerful moves.

Breloom = Under Level 40

Shroomish evolve into Breloom at level 23