A plant hanger assembly having multiple level plant trays, useful for growing plants in an upright configuration is provided for use with a trolley conveyor. A plurality of plant trays of selected size and shape are provided spaced apart along a vertical axis. A vertical support shaft has an upper end and a lower end. The plant trays may be circular in shape, with sloping sidewalls. The sloping sidewalls may be angled out sufficiently that the plant trays can be stacked in a nested configuration for storage. The plant trays include a base having grooved channels for transfer of water on the obverse side, and reinforcing ribs for strength, on the reverse side. Apertures between the obverse side and the reverse side allow excess water in an upper plant tray to drain downward into a plant tray therebelow. Shaft couplers are provided, with attachment rings or pins, to securely join the plant trays to the vertical support shaft. The plant hangers are adapted for attachment to and use with a trolley conveyor in a plant factory.