A tray is a shallow container used for growing microgreens. In the context of microgreen cultivation, the tray holds the growing medium (typically a thin layer of soil, coconut coir, or hemp mat), retains moisture, and provides the surface area across which seeds are spread for even germination.
The most common tray size is the 10-by-20-inch nursery flat, available in depths from one to two inches. Growing setups often use two trays: a perforated tray that holds the growing medium and a solid tray beneath that serves as a water reservoir for bottom-watering. This arrangement delivers moisture to the roots through capillary action without wetting the leaf surface, which reduces the risk of mold and damping off — a fungal condition that kills seedlings at the stem base.
Tray material and condition affect food safety and harvest quality. Plastic trays should be food-safe rated and free of cracks where bacteria can accumulate. Reusable trays need sanitizing between crops. Some growers prefer trays with textured bottoms that grip the growing medium and prevent it from shifting when the tray is moved. The depth of the tray determines root space: deeper trays allow longer growth periods but use more medium, while shallower trays are sufficient for fast-growing varieties harvested within seven to fourteen days.