This article revisists a doctoral research project (2015-2018) carried out via an industrial agreement for training through research (CIFRE) for a public interest group located on the "right bank" area of Bordeaux metropolis (Grand Projet des Villes Rive Droite, GPV), in France. It draws theoretical and practical lessons from the conduct of a landscape project aimed at "greening" the gardening practices of a group of public/private parks, "Parc des Coteaux". The ParcLAB (Laboratoire du Parc des Coteaux), an experimental action mechanism set up by the landscape researcher, constituted the main field of research. Based on a reflexive approach about the conditions of this experience, the author puts forward a hypothesis about the concept of "landscape garden management" and discusses its principles and orientations. Such gardening management of landscapes is based on double cooperation involving human actors cooperating among themselves, and involving the cooperation of these actors with non-human actors.