Effect of Nutrient Level On Production of Mixed Species Green Roof Modules

Green roofs, rooftops that are vegetated, are desirable for their numerous environmental benefits. The sedum vegetated green roof modular system is gaining popularity as a green roofing method due to its ease of delivery and installation and immediate rooftop aesthetic value. Sedum plants are tolerant of adverse rooftop conditions including drought, high heat, direct sunlight, wind and snow load. The expanding green roof market and high demand for modules has created a situation where current module production methods are unable to meet demand. The influence of two different rates of control release fertilizer (30 g and 70 g of Scott’s Osmocote Plus 15-9-12, 3-4 month formulation) and two different rates of soluble fertilizer in weekly applications (50 ppm and 200 ppm of 20-10-20 Jack’s Professional) on recently propagated modules (40 cm × 30 cm × 10 cm) containing equal proportions of five different Sedum species (0.1 g of 3-5 cm cuttings per species) were evaluated. These species were album, pachyclados, reflexum, rupestre, and tetractinum. All fertilizer treatments produced fully vegetated modules in six weeks under greenhouse conditions. Species response to the different fertilizer treatments varied, and by the end of the experiment species composition differed dramatically between the fertilizer programs. These findings suggest that there are complex interactions between fertility program and amount of species, and necessitate the need for comprehensive fertility studies with both a single species system and a mixed species system to optimize module production.