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The choice of plants for green roofs depends on factors such as substrate depth and climatic conditions such as temperature and precipitation rates. Two experiments were conducted in which plants were subjected to drought conditions and tested for their growth responses to potential limitations in the green roof environment. These limitations include different temperatures and various substrate types and depths. The first study combined the factors of temperature and drought on four species of Sedum. The second study tested 3 succulents and 2 herbaceous perennials under drought conditions in different substrate types and depths. The purpose of the temperature study was to determine if Sedums from different habitats have different physiological responses to variations in drought and temperature. Various temperature and irrigation combinations were tested on the 4 Sedums. The purpose of the substrate study was to identify the optimal and minimal substrate depth of 5 selected species which are commonly found on plants lists in North America. The results demonstrated the importance of considering substrate, depth, and drought conditions when planning the design of extensive roofs and selecting plant species. The experiments showed the variability in tolerance among drought tolerant species when subjected to other treatments. It was suggested that the original habitats and morphologies of selected taxa should be known when planning for extensive green roofs. It was determined that suitable plants for extensive green roofs include shallow-rooted perennials with low growth habits. Succulent communities predominated by Sedums will …