you find her in the old chateau
you have to defeat the gym leader in eterna city
gardenia is in eterna city, near the bottom.
go to Eterna city and defeat the gym leader(she has grass type pokemon).
after you batle the odeburgh gym leader you go to eterna city.
Pokemon Diamond, Pearl and Platinum has Eterna Forest.
eterna city gym leader gardenia she uses grass types
Simple. You need to beat the gym leader in Eterna City. She is only the second gym leader and her Pokemon are fairly easy.
Go to Eterna Forest at night. Only available on Pokemon Pearl.
The Eterna Forest
in eterna city
you go to the eterna forest
in eterna city