An assembly in use forming a tray for plant material includes a holder; and at least one insert which can be respectively placed in and removed from the holder. The insert includes at least one cell defining a plant position. The cell includes at least a wall and a bottom for accommodating content in the cell during use of the assembly. The at least one wall substantially encloses the plant position. The wall and/or bottom comprises an opening through which access is provided with means for removing the content of the cell, such as a pusher or a ram.