The invention relates to a process for pruning a row of plants supported by posts spaced by a distance d from each other along said row, using a machine comprising a straddling tunnel (5) equipped with a pruner (6) with two pruning harrows (7) disposed each respectively on one side of said tunnel and operable reversibly in an open state wherein they are moved apart, said process providing for driving the machine at a speed V along the row by placing said row within the tunnel (5) to prune it on each side between the harrows (7) and for operating said harrows in their open state upon the passage of each posts between them, the opening of the harrows (7) being operated by means of an automatic procedure (H) determined by a previous learning stage (E) using several successive manual openings (E1) of the harrows (7) to determine an opening time period (T
