Instructions
Travel to Route 36. Splash water on the bush blocking the path; a Sudowoodo will then attack you.
Defeat the Sudowoodo with one of your Pokemon. It is weak against Water-type Pokemon as well as status effects such as Sleep and Paralysis.
Speak with the girl near the tree, close to the bush; she will give you four Berry Pots as a reward.
Purchase one of the four types of fertilizer from the girl or from the flower shop in Goldenrod. Each type of fertilizer cost 200p.