You have to beat Goldenrod's leader, then go to a house in the northeastern part of town. Talk to the woman in the house and she will give you a watering can. Go use it on the "tree" in the path by the Ruins of Alph.
It is in Kanto
Azalea Town
Newbark town
hes in magondy town
pallet town in kanto
talk with a nerd in lavender town
east of mahogany town
mahogany town
Pallet town
its in azalea town
he is in pewter town in kanto
Lavender Town.