In response to a reader request for recommendations on gardens in the south of France, my only home resource, Secret Gardens of France, listed mostly private properties, almost all of which were near Lyon or farther north, so I did some research online.  The best websites I found were these…

for Provence near Arles

a comprehensive list for southeast France, with interactive maps

a comprehensive list for southwest France, with interactive maps

I like the last two because the Google maps show where the gardens are, making it easier to know which are closest to whichever town you may be headed for.