The invention comprises at least one spacer element (1) and a drainage collection channel (3), where the spacer element (1) is arranged in the channel (3), and a substrate contained inside a container element such as a plant pot or a bag is arranged on the spacer element (1). The spacer element (1) comprises a grid structure (1a) on the upper face of which is arranged the substrate-containing element； and supporting legs (1b) which extend from the lower face of the grid structure (1 a) and stand on the bottom of the channel (3). The spacer element (1) is fixed to sides (3b) of the channel (3) by means of anchoring frames (2).
