Assuming you mean Plumbago auriculata rather than any of the Ceratostigmas, in Britain, this plant is considered a houseplant or conservatory subject, but can be grown outside during summer months. At the end of summer, should be cut down and removed to a frost free greenhouse. Depending on which part of France you're in, your winter temperatures may well be lower than ours, so I'd follow the same ritual as if you were growing it here.