Baptiste Marin, Pierre Lherieau, Quentin Noyer and Julien Morin from the French city of Nantes spent three weeks in the Welsh capital in May.
The four gardeners honed their language as well as horticulture skills while working with the parks service at Cardiff Castle Nursery, Bute Park, Roath Park, Cardiff Bay and Parc Cefn Onn.
They teamed up with the community rangers, parks apprentices Maggie Szczerbnska and Anthony Davies and worked in the landscape design office.
Last year apprentices Ben Light and Alex Sibley went with landscape officer Mark Lawton to Nantes to help them finish their final year of the apprenticeship scheme.
Councillor Nigel Howells said: "These partnership arrangements show Cardiff Council's commitment to training and development opportunities."