What kind of vegetation is typically planted in extensive vegetated rooftops?

Extensive vegetated rooftops are designed with a specific focus on lightweight, low-maintenance vegetation that can thrive in limited soil depth and varying microclimate conditions found on rooftops. Drought-tolerant vegetation is the most suitable choice for these types of green roofs due to its ability to withstand periods of minimal water availability, which is crucial in a rooftop setting. This type of vegetation typically includes sedums, mosses, and other drought-resistant plants that have adapted to survive in harsh environments.

The other options, while beneficial in certain garden contexts, do not align well with the primary goals and conditions of extensive green roofs. Fruit-bearing plants require more substantial soil depth and maintenance for proper growth and fruit production. Flowering shrubs often need more water and soil than what is available on extensive roofs. Trees and large shrubs not only require deeper soil systems but can also impose significant structural loads, which are not advisable in extensive green roof design, where the emphasis is on minimizing weight and maintenance.