A tray has a plurality of receptacles. A receptacle is enabled to receive a container with a locking device. The container contains a potted plant. The locking device contains a protrusion, the protrusion being a protrusion on a wall of the container when the locking device is in a neutral position. The protrusion can move inwards and outwards from the neutral position relative to the wall when an inward or outward force is applied. The container is in a secured position in the receptacle when the protrusion mates with an opening in the receptacle. The protrusion has a slanted side allowing the protrusion to be lifted from the opening by rotating the container around a vertical axis.