Plant selection depends on the design intent for the roof, the climate and microclimate, irrigation, maintenance constraints and the depth of media. Shallow (less than 5″ deep) roofs without irrigation will have a relatively limited palate of plants that can be used, including sedums and a few other very drought-tolerant species. As roof media depth is increased, the roof becomes more garden-like and can support a broader range of plant species. Intensive roofs with media depth greater than 1-3′ can support trees and shrubs, as well as herbaceous annuals and perennials. More complicated plantings will increase maintenance and management requirements, including the use of irrigation.