Abstract: A support rail for use in supporting a planting tray during its initial growing period in a greenhouse. The support rail is especially suited for use with trays having a high-density matrix of small-sized soil plugs, and comprises a horizontally extending, vertically disposed web member and a pair of support members projecting from opposite sides of the web member at its lower extremity. The support members are angled downward from the horizontal so that a tray resting on support member will be supported along the tray's lower edges and not along the bottom surface. The rails are arranged in a uniformly spaced, parallel configuration, which provides stable support for a plurality of trays without providing a preferential growing environment for those soil plugs closest to the edges of the trays.