A tray (200) for growing organic material comprising a plurality of LEDs (204) is disclosed. The tray (200) comprises an upper side (202) and a lower side (206). The upper side (202) is arranged to carry a substrate (210) for growing organic material and the lower side (206) is arranged to radiate the light generated by the LEDs (204). The tray (200) comprises a structure which enables the tray (200) to radiate more heat, generated by the LEDs (204), at the upper side(202) than at the lower side(206) of the tray(200). The tray(200) enables to provide an improved nursery assembly (100), wherein the soil with organic material is heated up with the heat generated by the LEDs (204). In this way, the heat is not wasted to heat up the air but is used to heat up the soil such that it can have a higher average temperature than the air above the organic material.
