Abstract: A panel for a modular green roof system includes a bottom and four sides extending upwardly therefrom to provide an enclosure for growing medium, with a first side having a height above the bottom, the panel configured to accommodate an irrigation head. The bottom of the irrigation head is positioned below the height of the first side and connects with a water supply line running horizontally along the first side. A mold defining a first opening can be formed in the first side, the first opening configured to receive the irrigation head, the mold extending toward a side opposing the first side. A notch formed in a first side flange extending from the first side may alternatively help secure the irrigation head. The top of the irrigation head can be elevated above the height of the first side to irrigate the panel and nearby panels with pressurized water.