An improved modular green roof system for installation on a roof includes: (a) trays, each having a surface chosen from the group of sidewall, bottom and a combination of such surfaces, and having drainage openings that limit the movement of planting media through the surface while promoting maximum root growth and water and moisture transport through the surface, (b) a water management passage, (c) a structural member that extends across each of the trays and attaches to the opposing bottom sidewall to provide rigidity to each tray, (d) locking members for use with the trays, and wherein each of the trays have a locking opening configured to accommodate one of the locking members, (e) stacking members for use with the trays, and wherein each of the trays have a stacking opening configured to accommodate the insertion of one the stacking members, (f) a slope stabilization device, a portion of which is configured to be accommodated in water management passages, and (g) a water retention medium configured for placement below and in direct contact with the trays bottom surface.
