The 2012 ASHS Annual Conference

The effect of fertility on sedum green roof module production and maintenance was studied. Three starting proportions of cuttings and three fertility rates were evaluated for six popular green roof module sedum species. In only 8 weeks, 80% of modules were at least 95% vegetated and ready for sale using a moderate controlled-release fertilizer rate of 78 g/ft2. Final proportions of species may not be the same as initial proportions of species depending on which species are combined in modules. In a second study, the ability of inorganic and organic fertilizers to maintain green roof aesthetics was compared. Two different organic fertilizers (4N-0.9P-1.7K and 8N-2.2P-4.5K) were compared to an inorganic granular fertilizer (10N-4.4P-8.3K) and an inorganic controlled-release fertilizer (14N-6.1P-11.6K, 6-month formulation). Fertilizers were applied once at a rate of 2 lb N per 1000 ft2 or twice at a rate of 1 lb N per 1000 ft2 except for the controlled-release fertilizer which was applied only once at a rate of 2 lb N per 1000 ft2. Fertilizer treatments were rated visually based on foliage color and coverage. The single application inorganic granular fertilizer treatment performed the best, followed by the double application inorganic granular fertilizer treatment. The no fertilizer control and the controlled-release fertilizer performed the worst and the organic fertilizer treatments were intermediate. The single application of organic 8N-2.2P-4.5K fertilizer produced better results than the other three organic fertilizer applications.