Typically greenhouse crop production uses 85% of the floor area for growing crops. The present invention provides a fourfold increase in the usable growing area by using a conveyor to move plants around a closed loop 11, with a plurality of carriages mounted on the conveyor and at least one tray 7 configured to be received on each of the plurality of carriages, each tray 7 configured for growing at least one plant by means of hydroculture.