Urban green roof (GR) agriculture provides an alternative growing space to supply fresh produce and herbs to local markets or restaurants, which can also help to address food security concerns in cities, by providing nutritional produce in urban and often underserved locations. Although many vegetables can be grown on extensive GRs, few studies have evaluated the performance of edibles grown on green roof environments to those grown under typical field conditions. Unlike traditional agriculture, plants on extensive GRs are grown in a shallow engineered soil to reduce the weight load on the roof. Therefore, an experiment was conducted in 2023 on the Southern Illinois University – Carbondale Agriculture building extensive green roof and at the Horticulture Research Center. This experiment evaluated ‘Dazzling Blue’ and ‘Red Russian' Kale [Brassica oleracea (Acephala Group)], and ‘Green Wave’ Mustard (Brassica juncea) productivity in both an extensive green roof environment and open field conditions. Similar cultural practices were followed regarding plant spacing, fertilizer and water management in both systems. The experiment was setup as a CRD with two treatment locations evaluating three edible green varieties with four replications. Results indicated a significant yield cost for these leafy edibles when gown on the greenroof compared to the conventional field environment. Fresh weight of ‘Dazzling Blue’ and ‘Red Russian Kale were reduced by 85% and 80% when grown in the GR environment, respectively, while that for ‘Green Wave’ Mustard was decreased by 70%. Data for other growth variables, such as plant height and vigor, leaf count, and dry weight were also generally reduced in an extensive GR environment and will be presented and discussed further. Although our research indicates that extensive GRs do not provide similar yields for leafy green edibles as conventional field production, this alternative urban space used to grow fresh food for an urban community may more than make up for the loss in yield due to the various significant positive impacts that GRs can provide.
